specifications of any and all sanyo semiconductor co.,ltd. products described or contained herein stipulate the performance, characteristics, and functions of the described products in the independent state, and are not guarantees of the performance, characteristics, and functions of the described products as mounted in the customer ' s products or equipment. to verify symptoms and states that cannot be evaluated in an independent device, the customer should always evaluate and test devices mounted in the customer ' s products or equipment. any and all sanyo semiconductor co.,ltd. products described or contained herein are, with regard to "standard application", intended for the use as general electronics equipment. the products mentioned herein shall not be intended for use for any "special application" (medical equipment whose purpose is to sustain life, aerospace instrument, nuclear control device, burning appliances, transportation machine, traffic signal system, safety equipment etc.) that shall require extremely high level of reliability and can directly threaten human lives in case of failure or malfunction of the product or may cause harm to human bodies, nor shall they grant any guarantee thereof. if you should intend to use our products for new introduction or other application different from current conditions on the usage of automotive device, communication device, office equipment, industrial equipment etc. , please consult with us about usage conditi on (temperature, operation time etc.) prior to the intended use. if there is no consultation or inquiry before the intended use, our customer shall be solely responsible for the use. 32812 sy 20120207-s00002 no.a2022-1/6 LA5735MC overview the LA5735MC is a separately-excited step-d own switching regulator (variable type). functions ? time-base generator (300khz) incorporated. ? current limiter incorporated. ? thermal shutdown circuit incorporated. specifications absolute maximum ratings at ta = 25 c parameter symbol conditions ratings unit input voltage v in 34 v sw pin application reverse voltage v sw -1 v vos pin application voltage v vos -0.2 to 7 v allowable power dissipation pd max mounted on a circuit board.* 0.75 w operating temperature topr -30 to +125 c storage temperature tstg -40 to +150 c junction temperature tjmax 150 c * specified circuit board : 114.3 76.1 1.6mm 3 , glass epoxy board. caution 1) absolute maximum ratings represent the va lue which cannot be exceeded for any length of time. caution 2) even when the device is used within the range of absolu te maximum ratings, as a result of continuous usage under hig h temperature, high current, high voltage, or drastic temperature change, the reliability of the ic may be degraded. please contact us for the further details. recommended operating conditions at ta = 25 c parameter symbol conditions ratings unit input voltage range v in 4.5 to 32 v monolithic linear ic separately-excited step-down switching regulator (variable type) orderin g numbe r : ena2022
LA5735MC no.a2022-2/6 electrical characteristics at ta = 25 c, v in = 15v parameter symbol conditions ratings unit min typ max reference voltage v os i o = 0.3a 1.20 1.23 1.26 v reference pin bias current i fb 1 2 a switching frequency fosc 240 300 360 khz short-circuit protection circuit operating switching frequency fscp 15 khz saturation voltage vsat i out = 0.3a, v os = 0v 1 1.15 v maximum on duty d max v os = 0v 100 % minimum on duty d min v os = 5v 0 % output leakage current ilk sw out = -0.4v 200 a supply current iin v os = 2v 5 10 ma current limiter operating current i s 0.7 a thermal shutdown operating temperature tsd designed target value. * 165 c thermal shutdown hysteresis width tsd designed target value. * 15 c * design target value : design guarantee values are replaced with electrical measurements, and are not measured by temperature. package dimensions unit : mm (typ) 3424 pd max -- ta 0 0.2 0.4 0.6 0.8 1 --30 0 30 60 0.15 150 90 120 0.75 ambient temperature, ta - c allowable power dissipation, pd max - w mounted on a board designated board : 114.3 76.1 1.6mm 3 glass epoxy sanyo : soic8 4.9 3.9 6.0 12 8 0.835 0.375 0.2 0.42 1.27 0.175 1.75 max
LA5735MC no.a2022-3/6 pin assignment block diagram note : since the nc pins are not connected within the ic package, they can be used as connection points. application circuit example note: insome cases, the output may not turn on if power is app lied when a load is connected. if this is a problem, increase the value of the inductor. nc nc gnd nc v in nc sw out v os 1 v in 2 nc 5 nc 7 nc 8 nc reg. osc reset drive ocp tsd vref amp. comp. 3 sw ou t 4 v os 6 gnd v in sw out v os gnd + + l1 c1 r1 r2 c2 d1 LA5735MC c3
LA5735MC no.a2022-4/6 protection circuit functional descriptions 1. overcurrent protection function the overcurrent protection function detects, on a pulse-by-pulse basis, the output transistor current and turns off that output transistor current if it exceeds 0.7a in a pulse- by-pulse manner. 2. short circuit protection function this ic prevents the current from increasing when the ou tputs are shorted by setting the switching frequency to 15khz if the v os pin voltage falls below 0.8v. note : at startup, since the switching frequency will be 15khz while the v os pin voltage is 0.8v or lower, the current capacity is reduced. if the load is applied at startup and th e applications has trouble st arting, increase the value of the inductor to resolve this problem. timing chart limit current inductor current sw out voltage 0v 0.8v 1.23v 30khz 160khz v in voltage sw out voltage v os voltage
LA5735MC no.a2022-5/6 part selection and set 1. resistors r1 and r2 r1 and r2 are resistors to set the output voltage. when th e large resistance value is set, the error of set voltage increases due to the v os pin current. the output voltage may also in creases due to the leak current of switching transistor at light load. in consequence, it is e ssential to see r1 and r2 currnet to around 500 a. r1= 1.23v 500 a 2.4k we recommend values in the range 2.0 to 2.4k r2= v out 1.23v -1 r1 the following equation gives the output voltage set by r1 and r2. v o = (1+ r2 r1 ) 1.23v (typ) 2. capacitor c1, c2 and c3 the large ripple current flows through c1 and c2, so that the high-frequency low-impedance product for switching power supply must be used. do not use, for c2, a capacitor eith extremely small equivalent series resistance (esr), such as ceramic capacitor, tantalum capacitor. otherwise, the output waveform may develop abnormal oscillation. the c2 capacitance and esr value stabilization conditions are as follows: 1 2 c2 esr 20khz c3 is a capacitor for phase compensation of the feedback loop. abnormal oscillation may occur when the c2 capacitance value is small or the equivalent series resistance is small. in this case, a ddition od the capacitance of c3 enables phase compensation, contributing to stabilization of power supply. 3. input capacitor: effective-value current the ac ripple currents flowing in the input capacitor is large than that in the output capacitor. the equation expressing the effective-value current is as follo ws. use the capacitor within the rated current range. ic1= ) ir 12 1 ) vin vout 1 ( iout ( vin vout 2 2 + ? [arms] 4. output capacitor: ef fective-value current the ac ripple current flowing in the output capacitor is the triabgular wave. therefor e, its effective value is obtained from the following equation. select the output cap acitor so that it does not exceed the allowable ripple current value. ic2 = 1 2 3 v out (v in - v out ) l fsw v in [arms] fsw = switching frequency 300khz 5. choke coil l1 note that choke coil heating due to overload or load shorting may be a problem.the inductance value can be determined from the following equation once the input voltage, output voltage, and current ripple conditions are known. ir indicates the ripple current value. reference example : v in = 12v, v out = 5v, ir = 150ma l = v in - v out - vsat ir ton = 12 - 5.0 - 1.0 0.15 1.58 10 -6 68 h ton = t (( v in - v out - vsat )/( v out + vf )) + 1 toff = t - ton t : switching repetition period 3.33 s is assumed for the calculation vf : schottky diode forward voltage 0.4v is assumed for the calculation
LA5735MC ps no.a2022-6/6 6. inductance curr ent : peak value the ripple current peak value must be held within the rated current values for the inductor used. here, irp is the ripple current. irp can be determined from the following equation. reference example : v in = 12v, v out = 5v, i out = 0.5a, l = 68 h irp = i out + v in - v out - vsat 2l ton = 0.5 + 12 - 5.0 - 1.0 2 68 10 -6 1.58 10 -6 0.57a 7. inductance current : ripple current value here ir is the ripple current. ir can be determined from the following e quation. if the load current becomes less than one half the ripple current, the inductor current will become discontinuous. ir = v in - v out - vsat l ton = 12 - 5.0 - 1.0 68 10 -6 1.58 10 -6 0.15 a 8. diode d1 a schottky barrier diode must be used for this diode. if a fast recovery diode is used, it is possible that the ic could be destroyed by the applied reverse voltage due to the recovery and the on-state voltage. 9. diode current: peak current applications must be designed so that the peak value of the diode current remains within the rated current of the diode. the peak value of the diode current will be the same current as the peak value of the inductor current. 10. repetitive peak reverse voltage applications must be designed so that the repetitive peak reverse voltage remains within the voltage rating of the diode. here, v rrm is the repetitive peak reverse voltage. v rrm can be determined from the following equation. v rrm v cc since noise voltage and other terms will be added in actual operation, the voltage handling capacity of the device should be about 1.5 times that given by the above calculation. this catalog provides information as of march, 2012. specifications and information herein are subject to change without notice. sanyo semiconductor co.,ltd. assumes no responsib ility 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 sanyo semiconductor co.,ltd. products described or contained herein. sanyo semiconductor co.,ltd. strives to supply high-quality high-reliab ility pr oducts, however, any and all semiconductor products fail or malfunction with some probab ility. it is possible that these pr obab ilistic failures or malfunction could give rise to accidents or events that could endanger human lives, trouble that could give rise to smoke or fire, or accidents that could cause dam age to other property. when designing equipment, adopt safety measures so that these kinds of accidents or events cannot occur. such measures include but are not limited to protective circuits and error prevention circuits for safe design, redundant design, and structural design. upon using the technical information or products described herein, neither warranty nor license shall be granted with regard to intellectual property rights or any other rights of sanyo semiconductor co.,ltd. or any third party. sanyo semiconductor co.,ltd. shall not be liable for any claim or suits with regard to a third party's intellctual property rights which has resulted from the use of the technical information and products mentioned above. any and all information described or contained herein are subject to change without notice due to product/technology improvement, etc. when designing equip ment, refer to the "delivery specification" for the sanyo semiconductor co.,ltd. product that you intend to use. in the event that any or all sanyo semiconductor co.,ltd. products described or contained herein are controlled under any of applicable local export control laws and regulations, such products may require the export license from the authorities concerned in accordance with the above law. no part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or any information storage or retrieval system, or otherwise, without the prior written consent of sanyo semiconductor co.,ltd.
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