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unisonic technologies co., ltd lxxld50 cmos ic www.unisonic.com.tw 1 of 11 copyright ? 2011 unisonic technologies co., ltd qw-r502-474.b 0.8v reference ultra low dropout linear regulator ? description the utc lxxld50 is a 5a ultra low dropout linear regulator providing designers with well supply voltage for applications of nb and front-side-bus termination on motherboards. a control voltage for the circuitry and a main supply voltage for power conversion are needed as supply voltages to reduce power dissipation and provide extremely low dropout. the utc lxxld50 contains some function circuits. a power-on- reset (por) circuit monitors both supply voltages to prevent undesired operations. a thermal shutdown and curr ent limit circuits prevent this device from being damaged due to thermal and current over-loads. a pok indicates the output status with a pre-set time delay. it can control other converter for power sequence. the utc lxxld50 can be enabled by other power system. pulling and holding the en pin below 0.3v shuts off the output. the utc lxxld50 is ideal for applications,such as front side bus vtt (1.2v/5a), note book pc applications, and motherboard applications. ? features * low dropout v d =0.2v(typ.) @ i out =5a * low esr output capacitor * v ref =0.8v * high output accuracy : 1.5% over line, load and temperature * fast transient response * 1.2v, 1.5v, 1.8v, 2.5v output options by connecting adj to gnd and output voltage can be adjusted by external resistors * power-on-reset monitoring both supply voltages ( v cntl and v in pins) * protection function: internal soft-start current-limit protection under-voltage protection thermal shutdown with hysteresis over-voltage protection * power-ok output with a delay time * shutdown for standby or suspend mode * lead free available (rohs compliant) ? ordering information ordering number lead free halogen free package packing lxxld50l-sh2-r LXXLD50G-SH2-R hsop-8 tape reel note: xx: output voltage, refer to marki ng information.
lxxld50 cmos ic unisonic technologies co., ltd 2 of 11 www.unisonic.com.tw qw-r502-474.b ? marking information package voltage code marking hsop-8 25 : 2.5v ad: adj ? pin configuration ? pin description pin no. pin name description 1 gnd ground pin of the circuitry. all voltage levels are measured with respect to this pin. 2 adj this pin, when grounded, sets the output vo ltage by the internal feedback resistors; if external feedback resistors are used, the output voltage will be v out =0.8 (1+r1/r2) (v) where r1 is connected from vout to adj with kelvin sensing and r2 is connected from adj to gnd. a bypass capacitor may be connected with r1in parallel to improve load transient response. the recommended r2 and r1 are in the range of 100~10k ? . 3 v out 4 v out output of the regulator. please connect pi n 3 and 4 together using wide tracks. it is necessary to connect a output capacitor with this pin for closed-loop compensation and improving transient responses. 5 v in main supply input pins for power conversions. the exposed pad provide a very low impedance input path for the main supply voltage. please tie the exposed pad and vin pin (pin 8) together to reduce the dropout voltage. the voltage at this pins is monitored for power-on reset purpose. 6 v cntl power input pin of the control circuitry. connecting this pin to a +5v (recommended) supply voltage provides the bi as for the control circuitry. the voltage at this pin is monitored for power-on reset purpose. 7 p ok power-ok signal output pin. this pin is an open-drain output used to indicate status of output voltage by sensing fb voltage. this pin is pulled low when the rising fb voltage is not above the vpok threshold or the falling fb voltage is below the vpnok threshold, indicating t he output is not ok. 8 en enable control pin. pulling and holding th is pin below 0.3v shuts down the output. when re-enabled, the ic undergoes a new soft-start cycle . left this pin open, an internal current source 10ma pulls this pin up to v cntl voltage, enabling the regulator.
lxxld50 cmos ic unisonic technologies co., ltd 3 of 11 www.unisonic.com.tw qw-r502-474.b ? block diagram
lxxld50 cmos ic unisonic technologies co., ltd 4 of 11 www.unisonic.com.tw qw-r502-474.b ? absolute maximum rating parameter symbol ratings unit vcntl supply voltage (v cntl to gnd) v cntl -0.3 ~ 7 v vin supply voltage (v in to gnd) v in -0.3 ~ 3.3 v en and fb to gnd v i/o -0.3 ~ v cntl +0.3 v pok to gnd v pok -0.3 ~ 7 v average power dissipation p d 3 w peak power dissipation (<20ms) p peak 20 w junction temperature t j 150 c storage temperature t stg -65 ~ 150 c note: absolute maximum ratings are those values beyond which the device could be permanently damaged. absolute maximum ratings are stress ratings only and functional device oper ation is not implied. ? thermal characteristics parameter symbol ratings unit junction to ambient ja 40 c/w note: ja is measured with the component mounted on a high effe ctive thermal conductivity test board in free air. the exposed pad of sop-8-p is soldered directly on the pcb. ? recommended operating conditions parameter symbol ratings unit v cntl supply voltage v cntl 3.1 ~ 6 v v in supply voltage v in 1.1 ~ 3.3 v v cntl =3.35% 0.8 ~ 1.2 v output voltage v cntl =5.05% v out +0.8 ~ v in -0.2 v v out output current i out 0 ~ 6 a operating junction temperature t j -25 ~ 125 ? electrical characteristics (refer to the typical application circ uit. these specifications apply over, v cntl = 5v, v in = 1.5v, v out = 1.2v or v in = 1.8v, v out = 1.5v or v in = 2.1v, v out = 1.8v or v in = 2.8v, v out = 2.5v and t a = 0 ~ 70c, unless otherwise specified. typical values refer to t a = 25c.) parameter symbol test conditions min typ max unit supply current v cntl supply current i cntl en = v cntl, 0.4 1 8 ma v cntl shutdown current i sd en = gnd 200 380 a power-on-reset v cntl por threshold v cntl rising 2.7 2.9 3.1 v v cntl por hysteresis 0.4 v v in por threshold v in rising 0.8 0.9 1.0 v in por hysteresis 0.5 v output voltage reference voltage v ref adj =v out 0.8 v output voltage accuracy i out =0a ~ 5a, t j = -25 ~125c -1.5 +1.5 % line regulation v cntl =3.3 ~ 5.5v 0.06 0.3 % load regulation i out =0a ~ 5a 0.06 0.15 % dropout voltage i out = 5a, v cntl =5v, t j = 25c 0.2 0.25 v dropout voltage i out = 5a, v cntl =5v, t j = -50~125c 0.3 v
lxxld50 cmos ic unisonic technologies co., ltd 5 of 11 www.unisonic.com.tw qw-r502-474.b ? electrical characteristics (cont.) parameter symbol test conditions min typ max unit protection v cntl =5v, t j = 25c 7 8 9 a v cntl =5v, t j = -25 ~ 125c 6 a v cntl =3.3v, t j = 25c 6.3 6.7 8.8 a current limit i limit v cntl =3.3v, t j = -25 ~ 125c 6 a thermal shutdown temperature t sd t j rising 150 c thermal shutdown hysteresis 25 c under-voltage threshold adj falling 0.4 v over-voltage threshold v ovp /v normal output voltage up regulation voltage 125 % enable and soft-start en logic high threshold voltage v en rising 0.3 0.4 0.5 v en hysteresis 30 mv en pin pull-up current en=gnd 10 a soft-start interval t ss 1.2 ms power ok and delay p ok threshold voltage for power ok v pok v adj rising 90% 92% 94% v ref p ok threshold voltage for power not ok v pnok v adj falling 79% 81% 83% v ref p ok low voltage pok sinks 5ma 0.2 0.4 v p ok delay time t delay 1 1.5 10 ms adj adjust pin threshold 0.1 0.2 0.4 v
lxxld50 cmos ic unisonic technologies co., ltd 6 of 11 www.unisonic.com.tw qw-r502-474.b ? functional description power-on-reset a por (power-on-reset) circuit is designed to monitor the two supply voltages at v cntl pin and v in pin to avoid the unexpected operations. during powering on proce ss, the por circuit would initiate a soft-start process after the two supply voltages above their rising por thres hold voltages. the por function also pulls low the p ok pin regardless the output volta ge when the voltage at v cntl pin drops below its falling por threshold. internal soft-start the built-in soft-start circuit controls rise rate of the output voltage to limit the current surge at start-up. the soft-start interval is approximately 1.2ms (typ.). output voltage regulation the error amplifier compares a temperature-compensated 0.8v reference with the feedback voltage, which is characterized with high bandwidth and dc gain to prov ide fast transient response and less load regulation. the output voltage can be adjusted by an output nmos to get the preset voltage. the difference which is amplified by the error amplifier provides load current from v in pin to v out pin. current-limit the current-limit protection circuit is used to protect this device against the maximum current, which occurs in overload or short-circuit conditions. for the utc lxxld50 , the current is monitored through the output nmos. under-voltage protection (uvp) the utc lxxld50 monitors the voltage on internal feed back si gnal after soft-start process is finished. thus, the under-voltage circuit is inactive during soft-start. when the voltage on fb signal goes below the under-voltage threshold, the uvp circuit shuts off t he output immediately. last for a period, this device starts a new soft-start to regulate output. over-voltage protection (ovp) the utc lxxld50 monitors the output volt age. when the voltage on v out pin goes high beyond normal regulation voltage by 25%, the ovp circuit shuts off the output immediately. after a while, the lxxld50 starts a new soft-start to regulate output. thermal shutdown the thermal shutdown protection circuit is designed to pr event the junction temperat ure beyond a certain value. if the junction temperature becomes higher than +150c, the output nmos is turned off through a thermal sensor, allowing the device to cool down. the regulator regulates the output again through initiation of a new soft-start cycle after the junction temperature cools by 25c, resulting in a pulsed output during continuous thermal overload conditions. the average junction temperature is reduced by the 25 c hysteresis during continuous thermal overload conditions, making this device use longer. also, the power dissi pation should be externally limited to ensure junction temperature under +125c during normal operation. enable control if the en pin is applied to a logic low signal (v en < 0.3v), the output would be sh ut down. following a shutdown, a logic high signal re-enables the output through initiation of a new soft-start cycle. left open, this pin is pulled up by an internal current source (10 a typical) to enable operation. for a low cost-effectiveness, an external transistor is not required. power-ok and delay for the utc lxxld50 , the power-ok circuit indicates the status of the output voltage by monitoring the internal feedback voltage (v fb ). when the feedback voltage becomes e qual to the rising power-ok threshold (v pok ), an internal delay function starts to perform a delay time. at the end of the delay time, the ic shuts off the internal nmos of the pok to indicate the output is ok. when t he feedback voltage becomes equal to the falling power-ok threshold (v pnok ), the ic immediately turns on the nmos of the p ok to indicate the output is not ok without a delay time.
lxxld50 cmos ic unisonic technologies co., ltd 7 of 11 www.unisonic.com.tw qw-r502-474.b ? application information power sequencing less consideration could be taken into the power sequencing of v in and v cntl . but do not apply a voltage to v out for a long time when the main voltage applied at v in is not present. the reason is the internal parasitic diode from v out to v in conducts and dissipates power without protections due to the forward-voltage. output capacitor for the maximum device performance and improving system stability, transient response over temperature and current, a well-suitable output capacitor is needed. the selected output capacit or should be qualified perfect esr (equivalent series resistance) and capacitor value for a better system stability and load transient. the utc lxxld50 is designed with a programmable feedback compensation adjusted by an external feedback network for the use of wide ranges of esr and capacitance in all applicatio ns. the output capacitors can be ultra-low-esr capacitors, such as ceramic chip capacitors; low-esr bulk capacitors, such as solid tantalum, poscap, and aluminum electrolytic capacitors, and their values can be increased without limit. during load transients, the output capacitors, depending on the stepping amplitude and slew rate of load current, are used to reduce the slew rate of the current seen by the utc lxxld50 and help the device to minimize the variations of output voltage for good transient response. therefore, low-esr bulk capacitors are universally to be expected for the applications with large stepping load current. in addition, decoupling ceramic capacitors must be loca ted to the load and gnd as close as possible and the layout?s impedance should be maintained minimum. input capacitor the input capacitors should be chosen properly due to s upply current to protect the input rail against dropping during stepping load transients. because the parasitic inductor from the voltag e sources or other bulk capacitors to the vin pin limit the slew rate of t he surge currents. more parasitic induct ance needs more input capacitance. more capacitance reduces the variations of the v in pin voltage. for the utc lxxld50 , input capacitors with low-esr are not needed. ultra-low-esr capacitors (such as ceramic chip capacitors) are good options, and an aluminum electrolytic capacitor (>100 f, esr <300m ? ) is recommended as the input capacitor. feedback network in the following, the feedback network between v out , gnd and fb pins is shown in figure 1. it works with the internal error amplifier to provide proper frequency response for the linear regulator. as seen in figure 1, the esr is the equivalent series resistanc e of the output capacitor. the c out is ideal capacitance in the output capacitor. the v out is the setting of the output voltage.
lxxld50 cmos ic unisonic technologies co., ltd 8 of 11 www.unisonic.com.tw qw-r502-474.b ? typical application circuit 1. using an output capacitor with esr 18m ? adj mode p ok en gnd adj v out v out v in v cntl p ok en enable r3 1k c cntl 1f c in 100f c out 220f r1 1k c1 33nf r2 2k v out v in +1.5v v cntl +5v (in the range of 12 ~ 48nf) 7 8 2 4 3 5 1 6 fixed voltage mode
lxxld50 cmos ic unisonic technologies co., ltd 9 of 11 www.unisonic.com.tw qw-r502-474.b ? typical application circuit (cont.) 2. using an mlcc as the output capacitor adj mode fixed voltage mode v out (v) r1 (k ? ) r2 (k ? ) c1 (pf) 1.05 43 137.6 47 1.5 27 30.86 82 1.8 15 12 150
lxxld50 cmos ic unisonic technologies co., ltd 10 of 11 www.unisonic.com.tw qw-r502-474.b ? typical characteristics quiescent current,i q (ma) temperature, ( c) 20 40 60 80 100 120 -40 -20 0 0.6 0.7 0.8 1.0 0.9 1.1 v cntl supply current vs. junction temperature 140 reference voltage vs. junction temperature reference voltage,v ref (v) temperature, ( c) 20 40 60 80 100 120 -40 -20 0 0.79 140 0.793 0.796 0.799 0.805 0.802 output current, i out (a) output voltage, v out (mv) output voltage, v out (v) enable voltage, v en (v) power-ok voltage, v p-ok (v) pok delay time (s) output voltage, v out (v) v out1 power-ok voltage, v p-ok (v) v in = 1.5v, v cntl = 5v,v out = 1.2v -c out = 220f/6.3v, c in = 100f/6.3v, r l =1 v out v pok
lxxld50 cmos ic unisonic technologies co., ltd 11 of 11 www.unisonic.com.tw qw-r502-474.b utc assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all utc products described or contained herein. utc products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. the information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice.

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