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Ordering number : ENA1439
LA5757TP
Overview
Monolithic Linear IC
Separately-excited Step-down
Switching Regulator (Variable Type)
The LA5757TP is a separately-excited step-down switching regulator (variable type).
Features
* Output smoothing condenser can use a Low ESR condenser for the reliability improvement * High efficiency * Four external parts * Time-base generator (300kHz) incorporated * Current limiter incorporated * Thermal shutdown circuit incorporated * Soft start circuit incorporated
Specifications
Maximum Ratings at Ta = 25C
Parameter Input voltage Output current SW pin application reverse Allowable power dissipation Operating temperature Storage temperature Symbol VIN max IO max VSW Pd max Topr Tstg Mounted on a specified board* Conditions Ratings 34 1.5 -1 1.1 -30 to +125 -40 to +150 Unit V A V W C C
* Specified board: 114.3mm x 76.1mm x 1.6mm, glass epoxy board.
Recommended Operating Conditions at Ta = 25C
Parameter Input voltage range Symbol VIN Conditions Ratings 4.5 to 32 Unit V
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 (home appliances, AV equipment, communication device, office equipment, industrial equipment etc.). 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 applications outside the standard applications of our customer who is considering such use and/or outside the scope of our intended standard applications, please consult with us 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. 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.
40809 MS 20090326-S00004 No.A1439-1/6
LA5757TP
Electrical Characteristics at Ta = 25C, VO = 5V
Parameter Reference voltage Efficiency Switching frequency Line regulation Load regulation Output voltage temperature coefficient Ripple attenuation factor Current limiter operating voltage Thermal shutdown operating temperature Thermal shutdown hysteresis width Symbol VOS f VOLINE VOLOAD VO/Ta RREJ IS TSD TSD VIN = 15V, IO = 1.0A VIN= 8 to 20V, IO=1.0A VIN = 15V, IO = 0.5 to 1.5A Designed target value* f = 100 to 120Hz VIN = 15V Designed target value* Designed target value* 1.6 165 15 240 Conditions min 1.230 Ratings typ 1.255 83 300 40 10 0.5 45 360 100 30 max 1.280 V % kHz mV mV mV/C dB A C C Unit
* Designed target value: No measurement made.
Package Dimensions
unit : mm (typ) 3332
1.4
Pd max -- Ta
Specified board: 114.3x76.1x1.6mm3 glass epoxy board. With specified board
6.5
Allowable power dissipation, Pd max -- W
2.3
1.2 1.1 1
1.5
5.0
0.5
(5.5) 7.0
0.8
0.8
2.5
1.2
0.6
0.4 0.22
0.6 (0.65) 12 1.3 5 0.5 0.5
0.2 1.2
0.2 0 --30--20
0
20
40
60
80
100
120
140
Ambient temperature, Ta -- C
SANYO : TP5HFA
Pin Assignment
(1)VIN (2)SWOUT (3)GND (4)VOS (5)SS
No.A0951-2/5
LA5757TP
Block Diagram
VIN 1 Constnt Current Circuit Reg. OCP 2 SWOUT
OSC
RESET DRIVE
Comp.
TSD 2 VOS
Amp.
ON/OFF Comp. 0.4V
VREF
5 SS
3 GND
Application Circuit Example
L1
VIN
SWOUT
LA5757TP
C1 D1 C2
VOS SS
C3
GND
R2 R1
Notes: C3 is for the soft start function. Delete C3 and keep the SS pin open when the soft function is not necessary.
Description of Functional Settings
1. Calculation equation to set the output voltage This IC controls the switching output so that the VOS pin voltage becomes 1.255V (typ). The equation to set the output voltage is as follows:
R2 VO = 1+ x 1.255V(typ) R1
The VOS pin has the inrush current of 1A (typ). Therefore, the error becomes larger when R1 and R2 resistance values are large.
No.A0951-3/5
LA5757TP
2. Start delay function The SS pin has the internally-connected 10A (typ) constant-current supply. When the voltage of SS pin exceeds the threshold voltage, the regulator starts operation. As the threshold is 0.62V(typ), the start delay time can be calculated as follows: ex. For setting at 1F
Td = C x V 1 x 0.62 = = 28.2 msec 22 i
3. Soft start function The internal PWM waveform has the voltage value as shown in the right. If down-conversion from the voltage of VIN = 15V to 3.3V output to be made, for example, the PWM-ON duty has the value as shown below.
VOUT + VF PWMduty = = 25% VIN - Vsat + VF
1.5V
0.62V PWM wave
(Note that calculation is made with Vsat = 1V and VF = 0.2V) The output voltage of error amplifier, which is 3.3V, is the value with PWM = 25%, as calculated in the above equation, so that this voltage is determined as follows: Ver = (VPWM) x PWMduty + VPWML = 0.88V x 0.25 + 0.62V = 0.84V (VPWM is the PWM amplitude value or 0.88V(typ) while VPWML is the lower limit voltage of PWM waveform or 0.62V(typ)) SS pin and error amplifier output voltages are designed to prefer the lower voltages, so that VOUT will reach the designed regulation voltage in timing when the SS pin voltage exceeds the error amplifier output. Therefore, the soft strt time is calculated as follows:
Tss = C x VPWM x PWMduty C x 0.88 x PWMduty = 22A i
For the set conditions of C = 1F and PWMduty = 25%:
Tss = 1 x 0.88V x 0.25 = 10msec 22A
No.A0951-4/5
LA5757TP
Timing Chart
VIN
SWOUT
VOUT
Td
Tss
8 7 6 5 4 3 2
Overcurrent protection characteristic
VIN = 12V VO = 5V CIN = 1000F COUT = 470F L = 68H
90
Efficiency -- VIN
85
Output voltage, VO -- V
IO = 0.5 A
Efficiency -- %
80
1.5A
1.0A
75
70
65 1 0 60
0
0.4
0.8
1.2
1.6
2.0
0
10
20
30
40
Load current, IL -- A
1.6
VOsat -- ISW
Input voltage, VIN -- V
250
ISTB -- VIN
Output saturation voltage, VOsat -- V
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0
Standby current, ISTB -- A
200
150
100
50
0
0.25
0.5
0.75
1.0
1.25
1.5
0
10
20
30
40
Switch current, ISW -- A
Input voltage, VIN -- V
No.A0951-5/5
LA5757TP
1.0
LR -- IL
2.5
INR -- VIN
2.0
Load regulation, LR -- %
0.5
Input regulation, INR -- %
1.5
0
1.0
0.5
-0.5
0
-1.0
0
0.25
0.5
0.75
1.0
1.25
1.5
-0.5
0
5
10
15
20
25
30
Load current, IL -- A
Input voltage, VIN -- V
SANYO Semiconductor Co.,Ltd. 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 SANYO Semiconductor Co.,Ltd. products described or contained herein. SANYO Semiconductor Co.,Ltd. strives to supply high-quality high-reliability products, however, any and all semiconductor products fail or malfunction with some probability. It is possible that these probabilistic 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 damage 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. 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. Any and all information described or contained herein are subject to change without notice due to product/technology improvement, etc. When designing equipment, refer to the "Delivery Specification" for the SANYO Semiconductor Co.,Ltd. product that you intend to use. Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for volume production. 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.
This catalog provides information as of April, 2009. Specifications and information herein are subject to change without notice. PS No.A1439-6/6

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