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| zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 1 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated 60v high accuracy buck/boost/buck-boost led driver-controller with aec-q100 description the zxld1370 is an led driver controller ic for driving external mosfets to drive high current leds. it is a multi-topology controller enabling it to efficiently control the current through series connected leds. the multi- topology enables it to operate in buck, boost and buck- boost configurations. the 60v capability coupled with its multi-topology capability enables it to be used in a wide range of applications and drive in excess of 15 leds in series. the zxld1370 is a modified hysteretic controller using a patent pending control sch eme providing high output current accuracy in all three modes of operation. high accuracy dimming is achieved through dc control and high frequency pwm control. the zxld1370 uses two pins for fault diagnosis. a flag output highlights a fault, while the multi-level status pin gives further informati on on the exact fault. pin assignments tssop-16ep curve showing led current vs. t led 85? c 70? c i led 100% 10% t led thermal network response in buck configuration with: rth = 2k ? and th1=10k ? (beta =3900) re f tad rth th1 features ? 0.5% typical output current accuracy ? 6 to 60v operating voltage range ? led driver supports buck, boost and buck-boost ? configurations ? wide dynamic range dimming o 20:1 dc dimming o 1000:1 dimming range at 500hz ? up to 1mhz switching ? high temperature control of led current using tadj ? aec-q100 grade 1 ? available in ?green? molding compound (no br, sb) with lead free finish/ rohs compliant (note 1) note 1: eu directive 2002/95/ec (rohs). all applicable rohs exemptions applied. please visit our website at http://www.diodes.com/products/lead_free.html . typical application circuit buck-boost diagram utilizing thermistor and t adj
zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 2 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated pin descriptions pin name pin type (note 2) description adj 1 i adjust input (for dc output current control) connect to ref to set 100% output current. drive with dc voltage (125mv zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 4 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated absolute maximum ratings (voltages to gnd unless otherwise stated) symbol paramete r rating unit v in input supply voltage relative to gnd -0.3 to 65 v v aux auxiliary supply voltage relative to gnd -0.3 to 65 v v ism current monitor input relati ve to gnd -0.3 to 65 v v sense current monitor sense voltage (v in -v ism ) -0.3 to 5 v v gate gate driver output voltage -0.3 to 20 v i gate gate driver continuous output current 18 ma v flag flag output voltage (note 3) -0.3 to 40 v v pwm , v adj , v tadj , v gi , v pwm other input pins (note 3) -0.3 to 5.5 v t j maximum junction temperature 150 c t st storage temperature -55 to 150 c these are stress ratings only. operation outside the absolute maximum ratings may cause device failure. operation at the absolute maximum rating for extended periods may reduce device reliability. semiconductor devices are esd sensitive and may be damaged by expos ure to esd events. suitable esd precautions should be taken when handling and transporting these devices. package thermal data thermal resistance package typical unit junction-to-ambient, ja (note 4) tssop-16 ep 50 c/w junction-to-case, jc tssop-16 ep 23 c/w recommended operating conditions symbol paramete r performance/comment min max unit v in input supply voltage range normal operation 8 60 v functional (note 5) 6.3 v aux auxiliary supply voltage range (note 6) normal operation 8 60 v functional 6.3 v ism current sense monitor input range 6.3 60 v v sense differential input voltage v vin -v ism , with 0 v adj 2.5 0 450 mv v adj external dc control voltage applied to adj pin to adjust output current dc brightness control mode from 10% to 200% 0.125 2.5 v i ref reference external load current ref sourcing current 1 ma f max recommended switching frequency range (note 7) 300 1000 khz v tadj temperature adjustment (t adj ) input voltage range 0 v ref v f pwm recommended pwm dimming frequency range (note 4) to achieve 1000:1 resolution 100 500 hz to achieve 500:1 resolution 100 1000 hz t pwmh/l pwm pulse width in dimming mode pwm input high or low 0.002 10 ms v pwmh pwm pin high level input voltage 2 5.5 v v pwml pwm pin low level input voltage 0 0.4 v t j operating junction temperature range -40 125 c gi gain setting ratio for boost and buck-boost modes ratio= v gi /v adj 0.20 0.50 notes: 3.for correct operation sgnd and pgnd should always be connected together. 4. measured on high effective thermal c onductivity test board" according jesd51. 5. the functional range of v in is the voltage range over which the device will function. output current and device param eters may deviate from their normal values for v in and v aux voltages between 6.3v and 8v, depending upon load and conditions. 6. v aux can be driven from a voltage higher than v in to provide higher efficiency at low v in voltages, but to avoid false operation; a voltage should not be applied to v aux in the absence of a voltage at v in . 7. the device contains circuitry to control the switching frequency to approximately 400khz. the maximum and minimum operating frequency is not tested in production. zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 5 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated electrical characteristics (test conditions: v in = v aux = 12v, t a = 25c, unless otherwise specified.) symbol paramete r conditions min typ max units supply and reference paramete r s v uv- under-voltage detection threshold normal operation to switch disabled v in or v aux falling 5.2 5.6 6.3 v v uv+ under-voltage detection threshold switch disabled to normal operation v in or v aux rising 5.5 6 6.5 v i q-in quiescent current into v in pwm pin floating. output not switching 1.5 3 ma i q-aux quiescent current into v aux 150 300 a i sb-in standby current into v in . pwm pin grounded for more than 15ms 90 150 a i sb-aux standby current into v aux . 0.7 10 a v ref internal refe rence voltage no load 1.237 1.25 1.263 v v ref change in reference voltage with output current sourcing 1ma -5 mv sinking 100 a 5 v ref _ line reference voltage line regulation v in = v aux , 6.5v zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 7 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated typical characteristics ? buck mode ? r s = 150m ? ? l = 33h - i led = 1.5a 1.430 1.440 1.450 1.460 1.470 1.480 1.490 1.500 6.5 11 15.5 20 24.5 29 33.5 38 42.5 47 51.5 56 60.5 input voltage (v) figure 1: load current vs. input voltage & number of led 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds led curr ent (a) 0 100 200 300 400 500 600 700 800 900 1000 6.5 11 15.5 20 24.5 29 33.5 38 42.5 47 51.5 56 60.5 input voltage (v) figure 2: frequency vs. input voltage & number of led 1 led 3 leds 5 leds 7 leds 9 leds 11 le ds 13 leds 15 leds t = 25c v = v a au x in switching frequency (khz) 60% 65% 70% 75% 80% 85% 90% 95% 100% 6.5 11 15.5 20 24.5 29 33.5 38 42.5 47 51.5 56 60.5 input voltage (v) figure 3: efficiency vs. input & number of led efficiency zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 8 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated typical characteristics ? buck mode ? rs = 300m ? - l = 47h - i led = 750ma 0.715 0.720 0.725 0.730 0.735 0.740 6.5 11 15.5 20 24.5 29 33.5 38 42.5 47 51.5 56 60.5 input voltage (v) figure 4: i vs. input & number of led led 2 leds 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds led current (a) t = 25c v = v a aux i n 0 100 200 300 400 500 600 700 800 900 1000 input voltage (v) figure 5: frequency zxld1370 - buck mode - l47 h 2 leds 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds switching frequency (khz) t = 25c v = v a au x in 6.5 11 15.5 20 24.5 29 33.5 38 42.5 47 51.5 56 60.5 60% 65% 70% 75% 80% 85% 90% 95% 100% input voltage (v) figure 6: efficiency vs. input voltage & number of led 2 leds 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds t = 25c v = v a au x in efficiency 6.5 11 15.5 20 24.5 29 33.5 38 42.5 47 51.5 56 60.5 zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 9 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated typical characteristics ? boost mode ? i led = 350ma ? r s = 150m ? ? gi ratio = 0.23 0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400 6.5 10 13.5 17 20.5 24 27.5 31 34.5 38 41.5 45 48.5 input voltage (v) figure 7: i vs. input voltage & number of led led 3 leds 4 leds 6 leds 8 leds 10 leds 12 leds 14 leds 16 leds led curr ent (a) t = 25c v = v a au x in 50 100 150 200 250 300 350 400 450 500 6.5 10 13.5 17 20.5 24 27.5 31 34.5 38 41.5 45 48.5 input voltage (v) figure 8: frequency vs. input voltage & number of led 3 leds 4 leds 6 leds 8 leds 10 leds 12 leds 14 leds 16 leds switching frequency (khz) t = 25c v = v a au x in boosted voltage across leds approaching vin 60% 65% 70% 75% 80% 85% 90% 95% 100 % 6.5 10 13.5 17 20.5 24 27.5 31 34.5 38 41.5 45 48.5 input voltage (v) figure 9: efficiency vs. input voltage & number of led 3 leds 4 leds 6 leds 8 leds 10 leds 12 leds 14 leds 16 leds efficiency t = 25c v = v a au x in zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 10 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated typical characteristics ? buck-boost mode ? r s =150m ? - i led = 350ma - gi ratio = 0.23 0.330 0.335 0.340 0.345 0.350 0.355 0.360 0.365 0.370 6.5 8 9.5 11 12.5 14 15.5 17 input voltage (v) figure 10: led current vs. input voltage & number of led 3 leds 4 leds 5 leds 6 leds 7 leds 8 leds led current (a) 0 100 200 300 400 500 600 700 800 6.5 8 9.5 11 12.5 14 15.5 17 input voltage (v) figure 11: switching frequency vs. input voltage & number of led 3 leds 4 leds 5 leds 6 leds 7 leds 8 leds switching frequency (khz) 60% 65% 70% 75% 80% 85% 90% 95% 100% 6.5 8 9.5 11 12.51415.517 input voltage (v) figure 12: efficiency vs. input voltage & n umber of led 3 leds 4 leds 5 leds 6 leds 7 leds 8 leds efficiency zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 11 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information the zxld1370 is a high accuracy hysteretic inductive buck/ boost/buck-boost controller designed to be used with an external nmos switch for current-driving single or multiple series-connected leds. t he device can be configured to operate in buck, boost, or buck-boost modes by suitable conf iguration of the external components as shown in the schematics shown in the device operation description. device operation a) buck mode ? the most simple buck circuit is shown in figure 13 led current control in buck mode is achieved by sensing the coil current in the sense resistor rs, connected between the two inputs of a current monitor within the control loop block. an outpu t from the control loop drives the input of a comparator wh ich drives the gate of the external nmos switch transisto r m1 via the internal gate driver. when the switch is on, current flows from v in , via rs, led, coil and switch to ground. this current ramps up until an upper threshold value is reached. at this point gate goes low, the switch is turned off and the current flows via rs, led, coil and d1 back to v in . when the coil current has ramped down to a lower threshold value, gate goes high, the switch is turned on again and the cycle of events repeats, resulting in continuous oscillation. figure 13. buck configuration the average current in the led and coil is equal to the aver age of the maximum and minimum threshold currents. the ripple current (hysteresis) is equal to the difference between the thresholds. the control loop maintains the average led current at the set level by adjusting the thresholds continuously to forc e the average current in the coil to the value demanded by the voltage on the adj pin. this minimizes variation in output current with changes in op erating conditions. the control loop also attempts to minimize changes in switching frequency by varyi ng the level of hysteresis. the hysteresis has a defined minimum (typ 5%) and a maximum (typ 30%), the frequency may deviate from nominal in extreme conditions. loop compensation is achieved by a single external capacitor c2, connected between shp and sgnd. figure 14. operating waveforms (buck mode) ~15 v 0v v vin v vin -225mv 225mv /r s 0a gate v oltage ism voltage coil / led current t off t on zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 12 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) b) boost and buck-boost modes control in boost and buck-boost mode is achieved by sensing the coil current in the series resistor rs, connected between the two inputs of a current monitor within the control loop block. an outpu t from the control loop drives the input of a comparator wh ich drives the gate of the external nmos switch transisto r m1 via the internal gate driver. in boost and buck-boost modes, when the switch is on, current flows from v in , via rs, coil and switch to ground. this current ramps up until an upper threshold value is reached. at this point gate goes low, the switch is turned off and the current flows via rs, coil, d1 and led back to v in (buck-boost mode), or gnd (boost mode). when the coil current has ramped down to a lower threshold value, gate goes high, the switch is turned on again and the cycle of events repeats, resulting in continuous oscillation. the average current in the coil is equal to the average of the maximum and minimum threshold currents and the ripple current (hysteresis) is equal to the difference between the thresholds. figure 15. boost and buck-boost configuration the average current in the led is always less than the average current in the co il and the ratio between these currents is set by the values of external resistors r gi1 and r gi2 . the peak led current is equal to the peak coil current. the control loop maintains the average led current at the set level by adjus ting the thresholds and the hysteresis continuously to force the average current in the coil to the value demanded by th e voltage on the adj and gi pins. this minimises variation in output current with changes in operating conditions. loop co mpensation is achieved by a single external capacitor c2, connected between shp and sgnd. figure 16. operating waveforms (boost and buck-boost modes) note: in boost and buck-boost modes, average i led = average i coil x r gi1 /(r gi1 +r gi2 ) for more detailed descriptions of device operation and for c hoosing external components, please refer to the application circuits and descriptions in the later sections of this specification. ~15v 0 v v vin v vin -225mv 225 mv / r s 0 a gate voltage ism voltage coil current 225 mv / r s 0 a led current a verage led current t off t on zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 13 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated application information (continued) a basic zxld1370 application circuit is shown in figures 13 and 15. external component selection is driven by the characteristics of the load and the input supply, since this will determine the kind of topology being used for the system. component selection starts with the current setting procedure, the inductor/frequency setting and the mosfet selection. finally after selecting the freewheeling diode and the output capac itor (if needed), the application section will cover the pwm dimming and thermal feedback. setting the output current the first choice when defining the output current is whether the devic e is operating with the load in series with the sense resistor (buck mode) or whether the load is not in series with the sense resistor (boost and buck-boost modes). the output current setting depends on the choi ce of the sense resistor rs, the volt age on the adj pin and the voltage on the gi pin, according to the device working mode. the sense resistor rs sets the coil current i rs . the adj pin may be connected directly to the internal 1.25v reference (v ref ) to define the nominal 100% led current. the adj pin can also be overdriven with an external dc voltage bet ween 125mv and 2.5v to adjust the led current proportionally between 10% and 200% of the nominal value. adj and gi are high impedance inputs within their normal operat ing voltage ranges. an internal 2.6v clamp protects the device against excessive input voltage and limits the maximu m output current to approx imately 4% above the maximum current set by v adj if the maximum input voltage is exceeded. below are provided the details of the led current calculation bot h when the load in series with the sense resistor (buck mode) and when the load is not in series with the sense resistor (boost and buck-boost modes). in buck mode, gi is connected to adj which results in the average led current (i led ) equal to the average sens e resistor/coil current (i rs ). a loop gain compensation factor, k, compensates for gi being connected to adj. this gives the following equation for i led : = == ref adj s rs led v v r mv225 ki i where k= 0.97 ref adj s v v r mv218 = if adj (and gi pin) is directly connected to v ref , this becomes: s rs led r mv218 i i == therefore: led i mv218 s r = r s ism vin ref adj gi sgnd figure 17. buck configuration in boost and buck-boost mode gi is connected to adj through a voltage divider . the ratio of average led current (i led ) to average sense resistor/coil current is determined by voltage divider ratio (defined by the resistor divider) at the gi pin. ? ? = d1 i i led coil standard boost converter equation d1 ri riv sled s coil rs ? == ? sense resistor voltage now i led = = s ref adj adj gi r mv225 v v v v = s ref adj 2gi1gi 1gi r mv225 v v )r(r r + rearranging gives : ref adj led2gi1gi 1gi s v v i mv225 )r(r r r + = r s ism vin ref adj gi sgnd r gi2 r gi1 figure 18. boost and buck-boost connection zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 14 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) when the adj pin is directly connected to the ref pin, this becomes: led2gi1gi 1gi s i mv225 )r(r r r + = note that the average led current for a boost or buck-boost converter is always less than the average sense resistor current. for the zxld1370, the recommended potential divider ratio is given by: 50.0 ) 2gi r 1gi r( 1gi r 2.0 + it is possible to use a different combination of gi pin voltages and sense resistor values to set the led current. in general the design procedure to follow is: - define input conditions in terms of v in and i in - set output conditions in terms of led current and the number of leds - define controller topology ? buck, boost or buck-boost calculate the maximum duty-cycle as: buck mode minin v leds v max d = boost mode leds v minin v leds v max d ? = buck-boost mode minin v leds v leds v max d + = set the appropriate gi ratio according to the circuit duty and the max switch current admissible cycle limitations max d1 ) 2gi r 1gi (r 1gi r adj v gi v ? + = - set rgi1 as: ??? k200 1gi rk10 - calculate rgi2 as: 1gi rx max d1 max d 2gi r ? - calculate the sense resistor as: led i mv225 ) 2gi r 1gi (r 1gi r s r + = if the potential divider ratio is greater than 0.64, the device detects that buck-mode operation is desired and the output curr ent will deviate from the desired value. for example, as in the typical application circuit, in order to get i led = 350ma with irs=1.5a the ratio has to be set as: 23.0 ) 2gi r 1gi (r 1gi r adj v gi v rs i led i + = = zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 15 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) setting r gi1 = 33k ? gives =? = k110)1 gi v adj v ( 1gi r 2gi r this will result in: = + = m150 led i mv225 ) 2gi r 1gi (r 1gi r s r table 1 shows typical resistor values used to determine gi ratio with e24 series resistors table 1 gi ratio rgi1 rg2 0.2 30k 120k 0.25 33k 100k 0.3 39k 91k 0.35 30k 56k 0.4 100k 150k 0.45 51k 62k 0.5 30k 30k inductor/frequency selection recommended inductor values for the zxld1370 are in the range 22 h to 100 h. the chosen coil should have a saturation current higher than the peak sensed current and a continuous current rating above the required mean sensed current by at least 50%. the inductor value should be chosen to maintain operating duty cycle and switch 'on'/'off' times within the recommended limits over the supply voltage and load current range. the frequency compensation mechanism inside the chip tends to keep the frequency within the range 300khz ? 400khz in most of the operating conditions. nonetheless, the controller a llows for higher frequencies when either the number of leds or the input voltage increases. the graphs below can be used to select a recommended inductor to maintain the zxld1370 switching frequency within a predetermined range when used in different topologies. buck inductor selection: ? zxld1370 buck mode 1.5a minimum recommended inductor target switching frequency - 400khz 0 1 02 03 04 05 06 0 1 3 5 7 9 11 13 15 number of leds supply voltage (v) l=10h l=22h l=33h l=47h figure 19. 1.5a buck mode inductor selection for target frequency of 400 khz zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 16 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) ? zxld1370 buck mode 1.5a minimum recommended inductor ta r g et switching frequency > 500khz 0 1 02 03 04 05 06 0 1 3 5 7 9 11 13 15 nu m ber of leds supply voltage (v) l=10h l=22h l=33h l=47h figure 20. 1.5a buck mode inductor sel ection for target frequency > 500khz for example, in a buck configuration (v in =24v and 6 leds), with a load current of 1.5a; if the target frequency is around 400 khz, the ideal inductor size is l= 33h. the same kind of graphs can be used to select the right inductor for a buck configuration and a led current of 750ma, as shown in figures 21 and 22. ? zxld1370 buck mode 750ma minimum recommended inductor target switching frequency 400khz 0 1 02 03 0 4 05 06 0 1 3 5 7 9 11 13 15 number of leds supply voltage (v) l=33h l=47h l=68h l=100h figure 21. 750ma buck mode inductor selection for target frequency 400khz zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 17 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) ? zxld1370 buck mode 750ma minimum recommended inductor target switching frequency > 500khz 0 1 02 0 3 0 4 05 0 6 0 1 3 5 7 9 11 13 15 number of leds supply voltage (v) l=33h l=47h l=68h l=100h figure 22. 750ma buck mode inductor selection for target frequency > 500khz in the case of the buck-boost topology, the following graphs guide the designer to select the inductor for a target frequency of 400khz (figure 23) or higher than 500khz (figure 24). ? zxld1370 buck-boost mode 350ma minimum recommended inductor tar get switching frequency - 400khz 0 1 0 2 03 04 0 5 06 0 1 3 5 7 9 11 13 15 number of leds supply voltage (v) l=22h l=33h l=47h figure 23. 350ma buck-boost mode inductor selection for ta rget frequency 400khz zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 18 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) ? zxld1370 buck-boost mode 350ma minimum recommended inductor tar get switching frequency > 500khz 0 1 0 2 03 0 4 05 06 0 1 3 5 7 9 11 13 15 number of leds supply voltage (v) l=22h l=33h l=47h figure 24. 350ma buck-boost mode i nductor selection for targ et frequency > 500khz for example, in a buck-bust configuration (vin =10-18v and 4 leds), with a load current of 350ma; if the target frequency is around 400khz, the ideal inductor size is l= 33uh. the same size of inductor can be used if the target frequency is higher than 500khz driving 6leds with a current of 350ma from a vin =12-24v. in the case of the boost topology, the following graphs guide the designer to select the inductor for a target frequency of 400khz (figure 25) or higher than 500khz (figure 26). ? zxld1370 boost mode 350ma minimum recommended inductor target switching frequency - 400khz 0 1 0 2 03 0 4 05 06 0 1 3 5 7 9 11 13 15 numbe r of leds supply voltage (v) l=22h l=33h l=47h figure 25. 350ma boost mode inductor selection for target frequency 400khz zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 19 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) ? zxld1370 boost mode 350ma minimum recommended inductor target switching frequency > 500khz 0 1 0 2 03 0 4 05 06 0 1 3 5 7 9 11 13 15 number of leds supply voltage (v) l=22h l=33h l=47h figure 26. 350ma buck-boost mode inductor selection for target frequency > 500khz suitable coils for use with the zxld1370 may be selected from the mss range manufactured by coilcraft, or the npis range manufactured by nic components. the following websites may be useful in finding suitable components www.coilcraft.com www.niccomp.com www.wuerth-elektronik.de mosfet selection the zxld130 requires an external nmos fet as the main power switch with a voltage rating at least 15% higher than the maximum transistor voltage to ensure safe operation during the ringing of the switch node. the current rating is recommended to be at least 10% higher than the average transistor current. the power rating is then verified by calculating the resistive and switching power losses. switching p resistive pp + = resistive power losses the resistive power losses are calculated using the rms transistor current and the mosfet on-resistance. calculate the current for the different topologies as follows: buck mode led ix max d max mosfet i = ? boost / buck-boost mode led ix max d1 max d max mosfet i ? = ? the approximate rms current in the mosfet will be: buck mode d led i rms mosfet i = ? zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 20 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) boost / buck-boost mode led ix d1 d rms mosfet i ? = ? the resistive power dissipation of the mosfet is: onds rx 2 rms mosfet i resistive p ? ? = switching power losses calculating the switching mosfet's switching loss depends on many factors that influenc e both turn-on and turn-off. using a first order rough approximation, the switching power dissipation of the mosfet is: gate i load ix sw fx in 2 vx rss c switching p = where c rss is the mosfet's reverse-transfer capacitance (a data sheet parameter), f sw is the switching frequency, i gate is the mosfet gate-driver's sink/source cu rrent at the mosfet's turn-on threshold. matching the mosfet with the controller is primarily based on the rise and fall time of the gate voltage. the best rise/fall time in the application is based on many requirements, such as emi (conducted and radiated), switching losses, lead/circuit inductance, switching frequency, etc. how fast a mosfet can be turned on and off is related to how fast the gate capacitance of the mosfet can be charged and discharged. the relationship between c (and the relative total gate charge qg), turn-on/turn-off time and the mosfet driver current rating can be written as: i qg i cdv dt = ? = where dt = turn-on/turn-off time dv = gate voltage c = gate capacitance = qg/v i = drive current ? constant current source (for the given voltage value) here the constant current source? i ? usually is approximated wi th the peak drive current at a given driver input voltage. example 1) using the dmn6068 mosfet (v ds(max) = 60v, i d(max) = 8.5a): ? q g = 10.3nc at v gs = 10v zxld1370 i peak = i gate = 300ma ns35 ma300 nc3.10 peak i g q dt = = = assuming that cumulatively the rise time and fall time can account for a maximum of 10% of the period, the maximum frequency allowed in this condition is: t period = 20*dt ? f = 1/ t period = 1.43mhz this frequency is well above the max frequency the device can handle, therefore the dnm6068 can be used with the zxld1370 in the whole spectrum of frequencies recommended for the device (from 300khz to 1mhz). example 2) using the zxmn6a09k (v ds(max) = 60v, i d(max) = 12.2a): ? q g = 29nc at v gs = 10v zxld1370 i peak = 300ma ns97 ma300 nc29 peak i g q dt = = = zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 21 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) assuming that cumulatively the rise time and fall time can account for a maximum of 10% of the period, the maximum frequency allowed in this condition is: t period = 20*dt ? f = 1/ t period = 515khz this frequency is within the recommended frequency range the device can handle, therefore the zxmn6a09k is recommended to be used with the zxld1370 for frequencies from 300khz to 500khz). the recommended total gate charge for the mosfet used in conjunction with the zxld1370 is less than 30nc. junction temperature estimation finally, the zxld1370 junction temperature can be estimated using the following equations: total supply current of zxld1370: i qtot i q + f ? q g where i q = total quiescent current i q-in + i q-aux power consumed by zxld1370 p ic = v in ? (i q + f ? qg) or in case of separate voltage supply, with v aux < 15v p ic = v in ? i q-in + v aux ? (i q-aux + f ? qg) t j = t a + p ic ? ja = t a + p ic ? ( jc + ca) where the total quiescent current iq tot consists of the static supply current (iq) and the current required to charge and discharge the gate of the power mosfet. moreover the part of thermal resistance between case and ambient depends on the pcb characteristics. 0 0.5 1 1.5 2 2.5 -40-25-10 5 203550658095110125 ambient temperature (c) power dissipation (mw) figure 27. power derating curve for zxld1370 mounted on test board according to jesd51 zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 22 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) diode selection for maximum efficiency and performance, the rectifier (d1) should be a fast low capacitance schottky diode* with low reverse leakage at the maximum operating voltage and temperature. the schottky diode also provides better efficiency than silicon pn diodes, due to a combination of lower forward voltage and reduced recovery time. it is important to select parts with a peak current rating abov e the peak coil current and a continuous current rating higher than the maximum output load current. in particular, it is recommended to have a voltage rating at least 15% higher than the maximum transistor voltage to ensure safe operation during the ringing of the switch node and a current rating at least 10% higher than the average diode current. the power rating is verified by calculating the power loss through the diode. the higher forward voltage and overshoot due to reverse recovery time in silicon diodes will increase the peak voltage on the drain of the external mosfet. if a silicon diode is used, care should be taken to ensure that the total voltage appearing on the drain of the external mosfet, including supply ripple, does not exceed the specified maximum value. *a suitable schottky diode would be pds3100 (diodes inc). output capacitor an output capacitor may be required to limit interference or for specific emc purposes. for boost and buck-boost regulators, the output capacitor provides energy to the load when the freewheeling diode is reverse biased during the first switching subinterval. an output capacitor in a buck topology will simply reduce the led current ripple below the inductor current ripple. in other words, this capacitor changes the current waveform through the led(s) from a triangular ramp to a more sinusoidal version without altering the mean current value. in all cases, the output capacitor is chosen to provide a desired current ripple of the led current (usually recommended to be less than 40% of the average led current). buck: ppled ix led rx sw fx8 ppl i output c ? ? = boost and buck-boost ppled ix led rx sw f ppled ixd output c ? ? = where: ? i l is the ripple of the inductor current, usually 20% of the average sensed current ? i led is the ripple of the led current, it should be <40% of the leds average current ? f sw is the switching frequency (from graphs and calculator) ? r led is the dynamic resistance of the leds string (n times the dynamic resistance of the single led from the datasheet of the led manufacturer). the output capacitor should be chosen to account for derating du e to temperature and operating voltage. it must also have the necessary rms current rating. the minimum rms curr ent for the output capacitor is calculated as follows: buck 12 ppled i rms coutput i ? = ? boost and buck-boost max d1 max d led i rms coutput i ? = ? ceramic capacitors with x7r dielectric are the best choice due to their high ripple current rating, long lifetime, and performance over the voltage and temperature ranges. zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 23 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) input capacitor the input capacitor can be calculated knowing the input voltage ripple v in-pp as follows: buck ppin vx sw f led ix)d1(xd in c ? ? = use d = 0.5 as worst case boost ppin vx sw fx8 ppl i in c ? ? = buck-boost ppin vx sw f led ixd in c ? = use d = d max as worst case the minimum rms current for the output capacitor is calculated as follows: buck )d1(dxx led i rmscin i ? = ? use d=0.5 as worst case boost 12 ppl i rms cin i ? = ? buck-boost )d1( d x led i rmscin i ? = ? use d=d max as worst case zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 24 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) pwm output current control & dimming the zxld1370 has a dedicated pwm dimming input that allows a wide dimming frequency range from 100hz to 1khz with up to 1000:1 resolution; however higher dimming frequencies can be used ? at the expense of dimming dynamic range and accuracy. typically, for a pwm frequency of 1khz, the error on the current linearity is lower than 5%; in particular the accuracy is better than 1% for pwm from 5% to 100%. this is shown in the graph below: buck mode - l=33uh - rs = 150m ? - pwm @ 1khz 0.00 250.00 500.00 750.00 1000.00 1250.00 1500.00 0 102030405060708090100 pwm led current [ma] 0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% error pwm @ 1khz error figure 28: led current linearity and accuracy with pwm dimming at 1khz for a pwm frequency of 100hz, the error on the current linearity is lower than 2.5%; it becomes negligible for pwm greater than 5%. this is shown in the graph below: buck mode - l=33uh - rs = 150m ? - pwm @ 100hz 0.00 250.00 500.00 750.00 1000.00 1250.00 1500.00 0 102030405060708090100 pwm led current [ma] 0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% error pwm @ 100hz error figure 29: led current linearity and accuracy with pwm dimming at 100hz the pwm pin is designed to be driven by both 3.3v and 5v l ogic levels. it can be driven also by an open drain/collector transistor. in this case the designer can either use the inte rnal pull-up network or an external pull-up network in order to speed-up pwm transitions, as shown in the boost/ buck-boost section. zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 25 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) figure 30. pwm dimming from open collector switch figure 31. pwm dimming from mcu led current can be adjusted digitally, by applying a low frequency pwm logic signal to the pwm pin to turn the controller on and off. this will produce an average output current proportional to the duty cycle of the control signal. during pwm operation, the device remains powered up and only the output switch is gated by the control signal. the pwm signal can achieve very high led current resolution. in fact, dimming down from 100% to 0, a minimum pulse width of 2s can be achieved resulting in very high accuracy. while the maximum recommended pulse is for the pwm signal is10ms. pwm 0v < 10 ms 0v 2s gate < 10 ms 2 s figure 32. pwm dimming minimum and maximum pulse the device can be put in standby by taking the pwm pin to ground, or pulling it to a voltage below 0.4v with a suitable open collector npn or open drain nmos transistor, for a time exceeding 15ms (nominal). in the shutdown state, most of the circuitry inside the device is switched off and residual quiescent current will be typically 90a. in particular, the status p in will go down to gnd while the flag and ref pins will stay at their nominal values. fig 33. stand-by state from pwm signal zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 26 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) t adj pin - thermal control of led current the ?thermal control? circuit monitors the voltage on the t adj pin and reduces output current if the voltage on this pin falls below 625mv. an external ntc thermistor and resistor can therefore be connected as shown below to set the voltage on the t adj pin to 625mv at the required temperature threshold. this will give 100% led current below the threshold temperature and a falling current above it as shown in the gr aph. the temperature threshold can be altered by adjusting the value of rth and/or the thermistor to su it the requirements of the chosen led. the thermal control feature can be disabled by connecting t adj to ref. here is a simple procedure to design the thermal feedback circuit: 1) select the temperature threshold t threshold at which the current must start to decrease 2) select the thermistor th1 (both resistive value at 25 ? c and beta) 3) select the value of the resistor r th as r th = th at t threshold figure 34. thermal feedback network for example, 1) temperature threshold t threshold = 70 ? c 2) th1 = 10k ? at 25 ? c and beta= 3500 ? th = 3.3k ? @ 70 ? c 3) r th = th at t threshold = 3.3k ? over-temperature shutdown the zxld1370 incorporates an over-temperature shutdown circuit to protect against damage caused by excessive die temperature. a warning signal is generated on the status output when die tem perature exceeds 125c nominal and the output is disabled when die temperature exceeds 150c nomi nal. normal operation resumes when the device cools back down to 125c. zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 27 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) flag/status outputs the flag/status outputs provide a warning of extreme operating or fault conditions. flag is an open-drain logic output, which is normally off, but switches low to indicate that a warn ing, or fault condition exists. status is a dac output, which is normally high (4.5v), but switches to a lower voltage to indicate the nature of the warning/fault. conditions monitored, the method of detection and the nominal status output voltage are given in the following table: table 2 warning/fault condition severity (note 14) monitored parameters flag nominal status voltage normal operation h 4.5 supply under-voltage 1 v aux <5.6v l 4.5 2 v in <5.6v l 3.6 output current out of regulation (note 15) 2 v shp outside normal voltage range l 3.6 driver stalled with switch ?on?, or ?off? (note 16) 2 t on , or t off >100s l 3.6 device temperature above maximum recommended operating value 3 t j >125c l 1.8 sense resistor current i rs above specified maximum 4 v sense >0.32v l 0.9 notes: 14. severity 1 denotes lowest severity. 15. this warning will be indicated if the output power demand is higher than the available input power; the loop may not be ab le to maintain regulation. 16. this warning will be indicated if the gate pin stays at the same level for greater than 100us (e.g. the output transistor cannot pass enough current to reach the upper switching threshold). vref 0v 0a flag voltage status voltage normal operations severity 4.5v 3.6v 2.7v 1.8v 0.9v vaux uvlo - vin uvlo - stall - out of reg over temperature over current 0 1 2 3 4 figure 35. status levels in the event of more than one fault/warning condition occurring, the higher severity condition will take precedence. e.g. ?excessive coil current? and ?out of regulation? occurring to gether will produce an output of 0.9v on the status pin. if v adj >1.7v, v sense may be greater than the excess coil current threshold in normal operation and an error will be reported. hence, status and flag are only guaranteed for v adj <=v ref . zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 28 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) diagnostic signals should be ignored during the device start ? up for 100 s. the device start up sequence will be initiated both during the first power on of the device or after the pwm signal is kept low for more than 15ms, initiating the standby state of the device. in particular, during the first 100 s the diagnostic is signaling an over-current then an out-of-regulation status. these two events are due to the charging of the inductor and are not true fault conditions. vref 0v over c urrent 225m v/r 1 0a flag status coil current out of regulation 100us fig 36. diagnostic during start-up boosting v aux supply voltage in boost and buck-boost mode when the input voltage is lower than 8v, the gate volt age will also be lower 8v. this means that depending on the characteristics of the external mosfet, the gate voltage ma y not be enough to fully enhance the power mosfet. this boosting technique is particularly important when the output mosfet is operating at full current, since the boost circuit allows the gate voltage to be higher than 12v. this guarantees that the mosfet is fully enhanced reducing both the power dissipation and the risk of thermal runaway of the mosfet it self. an extra diode d2 and decoupling capacitor c3 can be used, as shown below in figure 36, to generate a boosted voltage at v aux when the input supply voltage at v in is below 8v. this enables the device to operate with full output current when v in is at the minimum value of 6v. in the case of a low voltage threshold mosfet, the bootstrap circuit is generally not required. fig 37. bootstrap circuit for boost and buck-boost low voltage operations the resistor r2 can be used to limit the current in the bootstrap circuit in order to reduce the impact of the circuit itself o n the led accuracy. the impact on the led current is usually a decrease of maximum 5% compared to the nominal current value set by the sense resistor. the zener diode d3 is used to limit the voltage on the v aux pin to less than 60v. due to the increased number of components and the loss of current accuracy, the bootstrap circuit is recommended only when the system has to operate continuously in conditions of low input voltage (between 6 and 8v) and high load current. other circumstances such as low input voltage at low load curren t, or transient low input voltage at high current should be evaluated keeping account of the external mosfet power dissipation. zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 29 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) over-voltage protection the zxld1370 is inherently protected against open-circuit load when used in buck configuration. however care has to be taken with open-circuit load conditions in buck-boost or boost c onfigurations. this is because in these configurations there is no internal open-circuit protection mechanism for the external mosfet. in this case an over-voltage-protection (ovp) network should be provided externally to the mosfet to avoi d damage due to open circuit conditions. this is shown in figure 38 below, highlighted in the dotted blue box. figure 38. ovp circuit the zener voltage is determined according to: vz = v ledmax +10% where v ledmax is maximum led chain voltage. if the leda voltage exceeds v z the gate of mosfet q2 will rise turning q2 on. this will pull the pwm pin low and switch off q1 until the voltage on the drain of q1 falls below vz. if the voltage at leda remains above v z for longer than 20ms then the zxld1370 will enter into a shutdown state. care should be taken such that the maximum gate voltage of the q2 mosfet is not exceeded. take care of the max voltage drop on the q2 mosfet gate. zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 30 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) pcb layout considerations pcb layout is a fundamental activity to get the most of the device in all configurations. in the following section it is possi ble to find some important insight to design with the zxld1370 both in buck and buck-boost/boost configurations. figure 39: circuit layout here are some considerations useful for the pcb layout: ? in order to avoid ringing due to stray inductances, the inductor l1, the anode of d1 and the drain of q1 should be placed as close together as possible. ? the shaping capacitor c1 is fundamental for the stability of the control loop. to this end it should be placed no more than 5mm from the shp pin. ? input voltage pins, vin and vaux, need to be decoupled. it is recommended to use two ceramic capacitors of 2.2uf, x7r, 100v (c3 and c4). in addition to these capacitors, it is suggested to add two ceramic capacitors of 1uf, x7r, 100v each (c2, c8), as well as a further decoup ling capacitor of 100nf close to the vin/vaux pins (c9). vin and vaux pins can be short-circuited when the device is used in buck mode, or can be driven from a separate supply. application examples example 1: 2.8a buck led driver in this application example, the zxld1370 is connected as a buck led driver. the schematic and parts list are shown below. the led driver is able to deliver 2.8a of led current with an input voltage range of 8v to 24v. in order to achieve high efficiency at high led current, a super barrier rectifier (sbr) with a low forward voltage is used as the free wheeling rectifier. this led driver is suitable for applications which require hi gh led current such as led projector, automatic led lighting etc. shp pin v in / v aux decou p lin g inductor, switch and freewheeling diode zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 31 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) figure 40. application circuit: 2.8a buck led driver table 3: bill of material ref no. value part no. manufacturer u1 60v led driver zxld1370 diodes inc q1 60v mosfet zxmn6a09k diodes inc d1 45v 10a sbr sbr10u45sp5 diodes inc l1 33h 4.2a 744770933 wurth electronik c1 100pf 50v smd 0805/0603 generic c2 1uf 50v x7r smd1206 generic c3 c4 c5 4.7f 50v x7r smd1210 generic r1 r2 r3 300m ? 1% smd1206 generic r4 400m ? 1% smd1206 generic r5 0 ? smd 0805/0603 generic typical performance efficiency vs input voltage 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 10 12 14 16 18 20 22 24 input voltage (v) efficiency (%) 1 led 2 led figure 41. efficiency led current vs input voltage 0 500 1000 1500 2000 2500 3000 10 12 14 16 18 20 22 24 input voltage (v) led current (ma) figure 42. line regulation zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 32 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) example 2: 400ma boost led driver in this application example, the zxld1370 is connected as a boost led driver. the schemat ic and parts list are shown below. the led driver is able to deliver 400ma of led current into 12 high-brightness leds with an input voltage range of 16v to 32v. the overall high efficiency of 92%+ makes it ideal for applic ations such as solar led street lighting and general led illuminations. figure 43. application circuit - 400ma boost led driver table4. bill of material ref no. value part no. manufacturer u1 60v led driver zxld1370 diodes inc q1 60v mosfet zxmn6a25g diodes inc q2 60v mosfet 2n7002a diodes inc d1 100v 3a schottky pds3100-13 diodes inc z1 47v 410mw zener bzt52c47 diodes inc l1 68h 2.1a 744771168 wurth electronik c1 100pf 50v smd 0805/0603 generic c3 c9 4.7f 50v x7r smd1210 generic c2 1f 50v x7r smd1206 generic r1 r2 560m ? 1% smd1206 generic r9 r10 33k ? 1% smd 0805/0603 generic r12 0 ? smd 0805/0603 generic r15 2.7k ? smd 0805/0603 generic zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 33 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) typical performance efficiency vs input voltage 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 16 18 20 22 24 26 28 30 32 input voltage efficiency figure 44. efficiency led current vs input voltage 0 50 100 150 200 250 300 350 400 450 16 18 20 22 24 26 28 30 32 input voltage led current figure 45. line regulation example 3: 700ma buck-boost led driver in this application example, the zxld1370 is connected as a buck-boost led driver. the schematic and parts list are shown below. the led driver is able to deliver 700ma of led current into 4 high-brightness leds with an input voltage range of 7v to 20v. since the buck-boost led driver handles an input voltage range from below and above the total led voltage, the versatile input voltage range make it ideal for automotive lighting applications. figure 46. application circuit - 700ma buck-boost led driver zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 34 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated applications information (continued) table 5: bill of material ref no. value part no. manufacturer u1 60v led driver zxld1370 diodes inc q1 60v mosfet zxmn6a25g diodes inc q2 60v mosfet 2n7002a diodes inc d1 100v 5a schottky pds5100-13 diodes inc z1 47v 410mw zener bzt52c47 diodes inc l1 22h 2.1a 744771122 wurth electronik c1 100pf 50v smd 0805/0603 generic c3 c9 4.7f 50v x7r smd1210 generic c2 1f 50v x7r smd1206 generic r1 r2 r3 300m ? 1% smd1206 generic r9 33k ? 1% smd 0805/0603 generic r10 15k ? 1% smd 0805/0603 generic r12 0 ? smd 0805/0603 generic r15 2.7k ? smd 0805/0603 generic typical performance efficiency vs input voltage 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 7 8 9 1011121314151617181920 input voltage efficiency figure 47. efficiency led current vs input voltage 0 100 200 300 400 500 600 700 800 7 8 9 10 11 12 13 14 15 16 17 18 19 20 input voltage led current figure 48. line regulation zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 35 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated ordering information device packaging status part marking reel quantity tape width reel size ZXLD1370EST16TC tssop-16ep active zxld 1370 yyww 2500 16mm 13? where yy is last two digits of year and ww is two digit week number package data tssop-16ep zxld1370 zxld1370 document number: ds32165 rev. 4 - 2 36 of 36 www.diodes.com march 2011 ? diodes incorporated a product line o f diodes incorporated important notice diodes incorporated makes no warranty of any kind, express or implied, with regards to this document, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose (and their equivalents under the laws of any jurisdiction). diodes incorporated and its subsidiaries rese rve the right to make modifications, enhanc ements, improvements, corrections or ot her changes without further notice to this document and any product described herein. diodes incorporated does not assume any liability arising out of the application or use of this document or any product described her ein; neither does diodes incorporated convey any license under its patent or trademark rights, nor the rights of others. any customer or us er of this document or products described herein in such applica tions shall assume all risks of such use and will agree to hold diodes in corporated and all the companies whose products are represented on diodes incorporated website, harmless against all damages. diodes incorporated does not warrant or accept any liability what soever in respect of any pr oducts purchased through unauthoriz ed sales channel. should customers purchase or use diodes in corporated products for any unintended or unauthorized application, customers shall i ndemnify and hold diodes incorporated and its representatives harmless a gainst all claims, damages, expens es, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application. products described herein may be covered by one or more united states, international or foreign patents pending. product names and markings noted herein may also be covered by one or mo re united states, international or foreign trademarks. life support diodes incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the chief executive officer of diodes incorporated. as used herein: a. life support devices or syst ems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when prop erly used in accordance with instructions for use provided in the labeling can be reasonably expected to re sult in significant injury to the user. b. a critical component is any component in a life support devic e or system whose failure to perform can be reasonably expect ed to cause the failure of the life support device or to affect its safety or effectiveness. customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support dev ices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of diodes incorporated products in such safety-cri tical, life support devices or systems, notwithstanding any devic es- or systems- related information or support that may be provided by diodes inco rporated. further, customers must fully indemnify diodes inc orporated and its representatives against any damages aris ing out of the use of diodes incorporated products in such safety-critical, life su pport devices or systems. copyright ? 2011, diodes incorporated www.diodes.com |
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