input parameter conditions min. typ. max. units input voltage range 7.0 12 16.0 vdc maximum input voltage 0.5 sec 20.0 vdc input filter internal capacitor output parameter conditions min. typ. max. units output voltage range v in = 16v 2 14 vdc output current see model selection guide output current accuracy see model selection guide output power see model selection guide ef ciency see model selection guide capacitive load 47 f operating frequency 60 400 khz ripple & noise (20 mhz) see model selection guide temperature coef cient ?.03 %/ c thermal impedance natural convection +35 c/w output short circuit regulated at rated output current environmental parameter conditions min. typ. max. units operating temperature range ambient -40 +25 +85 c case +105 storage temperature range -40 +125 c cooling free air convection humidity rh, non-condensing 95 % lead temperature (solder) 1.5 mm from case for 10 sec 260 ? physical case size 0.50 x 0.40 x 0.27 inches (12.70 x 10.16 x 6.85 mm) case material non-conductive black plastic (ul94-v0) weight 0.064 oz (1.8g) remote on/off control parameter conditions min. typ. max. units dc/dc on open or 0.3v < v adj <1.25v dc/dc off v adj <0.15v remote pin drive current v adj = 1.25v 1 ma quiescent input current (shutdown mode) v in = 16v 25 a pwm dimming parameter conditions min. typ. max. units operation frequency recommended maximum 1.0 khz switch on time 200 ns switch off time 200 ns analog dimming parameter conditions min. typ. max. units input voltage range at v adj input (pin 7) 0.0 1.25 vdc output current adjustment 25 100 % control voltage range limits on 0.30 1.25 vdc off 0.0 0.15 drive current v adj = 1.25v 1.0 ma emc compliance emi/rfi radiated/conducted en 55015 (cispr22) electrostatic discharge (esd) class a iec/en 61000-4-2, -6, -8 rf field susceptibility class a iec/en 61000-4-3 electrical fast transients/bursts on mains class a iec/en 61000-4-4 ems immunity en61547 reliability speci cations parameter conditions min. typ. max. units mtbf mil hdbk 217f, 25 c, gnd benign 3.3 mhours micropower direct 292 page street suite d stoughton, ma 02072 usa t: (781) 344-8226 f: (781) 344-8481 e: sales@micropowerdirect.com w: www.micropowerdirect.com www.micropowerdirect.com electrical speci cations speci cations typical @ +25?, nominal input voltage & rated output current, unless otherwise noted. speci cations subject to change without notice. LDM12-xx-xxx miniature, wide input constant current dc/dc led drivers key features: constant current output wide 7v to 16v input range 93% ef ciency miniature minidip case 300 ma to 1a output meets en 60950 ?3.3 mhrs mtbf digital & analog dimming!
model selection guide 292 page street ste d stoughton, ma 02072 tel: (781) 344-8226 fax: (781) 344-8481 e-mail: sales@micropowerdirect.com www.micropowerdirect.com typical connection: dc/dc input model number input output maximum power (w) ripple & noise (mv p-p, max) ef ciency (%, typ) package voltage (vdc) voltage (vdc) current range range max (ma) accuracy (%) LDM12-04-300 7.0 - 16.0 2.0 - 14.0 300 ? 4.2 120 93 8 -pin minidip LDM12-05-350 7.0 - 16.0 2.0 - 14.0 350 ? 4.9 150 93 8 -pin minidip LDM12-07-500 7.0 - 16.0 2.0 - 14.0 500 ? 7.0 200 93 8 -pin minidip LDM12-08-600 7.0 - 16.0 2.0 - 14.0 600 ? 8.4 200 93 8 -pin minidip LDM12-10-700 7.0 - 16.0 2.0 - 14.0 700 ? 9.8 250 93 8 -pin minidip LDM12-14-1000 7.0 - 16.0 2.0 - 14.0 1,000 ? 14.0 250 93 8 -pin minidip notes: 1. a reversed power source could damage the unit. 4. the v adj input should be left open if not used. grounding v adj will shut the unit down. connecting v adj to v in may damage the unit. 2. no connection should be made between input ground and the output. 3. these are step-down devices, the maximum output open voltage is equal to the input voltage. 5. exceeding the speci ed maximum output power could cause damage to the unit. typical connection: ac/dc input connection notes: to comply with en61000-4-5, a tvs should be installed before the input lter components. a 3.0smcj15a or smcj16a is recommended. the tvs max clamping voltage (@max peak pulse current v c ) must be 20v. this will prevent any surge from exceeding the maximum input of the driver (20 vdc). exceeding the maximum input rating could damage the driver. the lter shown (c 1 , c 2, c 3 and l 1 ) will help to meet conducted emission requirements. with the addition of the lter, the unit should meet the levels of en 55015. connection notes: this is a distributed (or two-stage) ac connection. in this con guration, the ac line in (85 to 264 vac) is connected to the mpm-20s-15epb , a compact 20w ac/dc power supply. the mpm-20s-15epb provides a tightly regulated 15 vdc output at 1,330 ma. the 15 vdc output powers the led driver. the two stage approach can simplify the safety approval process (most ac/dc power supplies on the market are approved to en 60950) and may increase design ex- ibility. besides the output voltage/current ratings, other speci cations to consider when selecting the input ac/dc supply might include input range, case size, ef ciency, emi ratings and operating temperature range. note: the output current adjustment circuit shown in both connection diagrams is discussed on page 4.
micropower direct 292 page street ste d stoughton, ma 02072 tel: (781) 344-8226 fax: (781) 344-8481 e-mail: sales@micropowerdirect.com www.micropowerdirect.com pwm output current control an led operates at its maximum ef ciency when operated at the rated drive current speci ed by the manufacturer. operating an led at lower than its rated forward current not only decreases the system ef ciency; but may cause color (or wave- length) shifting. in illumination applications, this could cause visible changes to lighting. a preferred method is using pulse width modula- tion (pwm). as shown at left, the output current is adjusted by applying a pwm signal to the v adj input. by varying the signal duty cycle the average output current is adjusted up or down. to avoid visible icker, the pwm signal should be greater than 200 hz. for duty cycles (dpwm) between 0.1 and 1, the output current is derived by the formula: iixd nom max pwm = the v adj input may be driven via an open collec- tor transistor (as shown). the diode and resistor suppress high amplitude negative spikes that may be caused by the drain-source capacitance of the transistor. negative spikes on the control input of the unit could cause errors in output current or erratic operation. the v adj input can also be driven by the open drain output of a microcontroller. again, any high amplitude negative spikes that may be caused by the drain- source capacitance of the fet must be supressed. pwm control signals pwm dimming application a simple method of achieving digital (or pwm) dimming is by using a 555 timer to apply a series of pulses to the v adj input, as illustrated above. the 555 oper- ates over a supply voltage range of 4.5 vdc to 18vdc. here it is connected to the 15 vdc output of the sr7805 switching regulator (this is also the v in of the led driver). care should be taken to minimize ripple at the v cc input. excess ripple could cause timing errors. the timer is connected for astable (free run) operation. the frequency is set by r 1 , r 2 and c 4 . the timing capacitor (c 4 ) charges through r 1 and d 2 . when it reaches the level of 2 /3 v cc , the discharge pin (pin 7) goes low and c 4 will discharge through d 1 and r 2 to the internal discharge transistor. when the c 4 voltage drops to 1 /3 v cc , the discharge pin goes high and c 4 begins to charge again. the formulas for calculating the frequency and duty cycle are included in the mpd application note driving leds? the diodes (d 1 and d 2 ) allow duty cycles below 50% to be set. diode d 1 bypasses r 2 while c 4 is charging. diode d 2 is optional (but recommended), essentially blocking r 2 during the charge period. theoretically, this circuit will allow for duty cycles over a range of approximately 5% to 95%. if manual adjustment is desired, a potentiometer may be substituted for r 2 (with some adjustment of the circuit). the size of c 4 is generally not critical, but it should be as low leakage as pos- sible. in order to avoid excessive current ow through the internal discharge transistor, it is recommended that r 1 be at least 5 k .
micropower direct we power your success - for less! 292 page street ste d stoughton, ma 02072 tel: (781) 344-8226 fax: (781) 344-8481 e-mail: sales@micropowerdirect.com www.micropowerdirect.com notes: all dimensions are typical in inches (mm) tolerance x.xx = ?.02 (?.50) pin 1 is marked by a ?ot or indentation on the top of the unit mechanical dimensions analog output current control (v cnt = 5v) in the second circuit, the 5 vdc regulator (sr 2 ) is replaced by the shunt regulator (d 1 ) circuit connected in parallel with the resis- tor network. the regulator will maintain the voltage across r 2 and r 3 at 2.5 vdc, insuring that the 1.25 vdc limit on the v adj pin will not be exceeded. when using the analog control input, the nominal output current is equal to: . iix v 125 nom max adj = the v adj input should be left open if not used. grounding v adj will shut the unit down. connecting v adj to directly to +v in may damage the unit. analog output current control (5 - 16 vdc in) pin connections pin function 1+v in +dc supply 4 +led led anode conn. 5 -led led cathode conn. 7v adj pwm, on/off 8-v in -dc supply the output current of the unit can also be set by adjusting the voltage level on the v adj input to a value between 0.3v to 1.25v (i out will vary from 25% to 100% of rated output current). care must be taken not to exceed 1.25v on this input, or the driver may be damaged. a simple analog circuit using two low cost, switching regulators is shown at left. w orking from inputs that can range from 20 to 32 vdc,the top regulator (sr 1 ) keeps the input to the led driver at 15 vdc. the other regulator (sr 2 ), driven off the same input line maintains the control voltage (for the v adj input) at 5 vdc. the resister network of r 1 and r 2 can now be used to set the output current level of the led driver. this level is equal to: v rr r xv 12 2 adj ctrl = + get a full explanation of the circuits in this datasheet and more in driving leds ? available free at the mpd website
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