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Ordering number : ENA0717C
Monolithic Linear IC
LA5744
Overview
Separately-Excited Step-Down
Switching Regulator (Variable Type)
The LA5744 is a separately-excited step-down switching regulator (variable type).
Functions
* High efficiency. * 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 Maximum output current SW pin application reverse voltage Allowable power dissipation Symbol VIN IO max VSW Pd max1 Pd max2 Operating temperature Storage temperature Junction temperature Topr Tstg Tj max No heat sink Infinite heat sink Conditions Ratings 30 3 -1 1.75 7.5 -30 to +125 -40 to +150 150 Unit V A V W W C C C
* Specified circuit board : 76.1x114.3x1.6mm3 : Copper foil ratio 60% FR4
Recommended Operating Conditions at Ta = 25C
Parameter Input voltage range Symbol VIN Conditions Ratings 4.5 to 28 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.
52307 MS PC 20070522-S00004 / 42507 MS PC / 31407 MS PC / 30707 MS PC 20070215-S00001 No.A0717-1/5
LA5744
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 * Design target value : No measurement made. TSD Designed target value. * 15 C RREJ IS TSD f = 100 to 120Hz VIN = 15V Designed target value. * 3.1 165 45 dB A C Symbol VOS f VOLINE VOLOAD VO/Ta Conditions min VIN = 15V, IO = 1.0A VIN = 15V, IO = 1.0A VIN = 15V, IO = 1.0A VIN = 8 to 20V, IO = 1.0A VIN = 20V, IO = 0.5 to 1.5A Designed target value. * 240 1.20 Ratings typ 1.23 83 300 40 10 0.5 360 100 30 max 1.26 V % kHz mV mV mV/C Unit
Package Dimensions
unit : mm (typ) 3343
10.0
Pd max -- Ta
10.4MAX 3.6 10.0
4.5 1.3
Allowable power dissipation, Pd max -- W
8.0 7.5
100x100x1.5mm3
Infinite heat sink jc=5C
2.7
6.0 5.6
50x50x1.5mm3 Al heat sink mounting torque 39Ncm silicone grease applied
40 60 80 100 120 140 160 MSG07021
15.0
(8.8)
15.3
4.0 3.3 2.0 1.75
30x30x1.5mm3 No heat sink
21.7
0.9 2.7 1 2 5 0.8 (1.6) 1.7 0.4 4.5 8.4
23.0
0 -30 -20
0
20
Ambient temperature, Ta -- C
SANYO : 220-5HK
Pin Assignment
(1) VIN (2) SWOUT (3) GND (4) VOS (5) SS
No.A0717-2/5
LA5744
Block Diagram
VIN 1 Constant current circuit Reg. OCP
2 SWOUT
OSC
Reset
Drive
Comp.
TSD 4 VOS VREF
ON/OFF Comp. 0.4V 5 SS 3
Amp.
GND
Application Circuit Example
L1 22H
VIN
SWOUT
LA5744
C1 470F /50V D1 SBD C2 390F
VOS SS
C3 1F
GND
R2 R1
Notes : 1. C3 is for the soft start function. Delete C3 and keep the SS pin open when the soft start function is not necessary. 2. In some cases, the output may not turn on if power is applied when a load is connected. If this is a problem, increase the value of
the inductor.
No.A0717-3/5
LA5744
Protection Circuit Functional Descriptions 1. Overcurrent protection function The overcurrent protection function detects, on a cycle-by-cycle basis, the output transistor current and turns off that output transistor current if it exceeds 3.1A.
Limit current Inductor current
SWOUT voltage
2. Short circuit protection function This IC prevents the current from increasing when the outputs are shorted by setting the switching frequency to 30kHz if the VOS pin voltage falls below 0.8V. Note 3 : If the soft start function is not used, the IC will start up with the overcurrent protection function operating. At this time, the switching frequency will be cut in half. This means that the switching frequency will be 15kHz at startup. Note 4 : Since the switching frequency becomes 30kHz when the VOS pin voltage falls under 0.8V, the current capacity is reduced. If a load is applied with the VOS pin voltage over 0.8V, the inductance value operates at 22H. If a load is to be applied when this voltage is under 0.8V, the inductance value must be increased.
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 1.23V (typ). The equation to set the output voltage is as follows :
R2 VO = 1+ x 1.23V(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. 2. Startup Delay Function The output voltage rises when the internal voltage reaches 0.4V (typical). Until that point, a capacitor is charged from an internal 10A (typical) constant-current supply. The startup delay time can be calculated as shown below Example : Assume a 1F capacitor is used.
Td = C x V 1F x 0.4 = = 40 ms i 10A
No.A0717-4/5
LA5744
Timing Chart
VIN voltage
30kHz
300kHz
SWOUT voltage 1.23V 0.8V VOS voltage 0V Td
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This catalog provides information as of May, 2007. Specifications and information herein are subject to change without notice. PS No.A0717-5/5

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