BAT-54 National Semiconductor Corporation, BAT-54 Datasheet

BAT-54

Manufacturer Part Number

BAT-54

Description

N-channel Fet Synchronous Buck Regulator Controller For Low Output Voltages

Manufacturer

National Semiconductor Corporation

Datasheet

1.BAT-54.pdf (22 pages)

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LM2727/LM2737

N-Channel FET Synchronous Buck Regulator Controller

for Low Output Voltages

General Description

The LM2727 and LM2737 are high-speed, synchronous,

switching regulator controllers. They are intended to control

currents of 0.7A to 20A with up to 95% conversion efficien-

cies. The LM2727 employs output over-voltage and under-

voltage latch-off. For applications where latch-off is not de-

sired, the LM2737 can be used. Power up and down

sequencing is achieved with the power-good flag, adjustable

soft-start and output enable features. The LM2737 and

LM2737 operate from a low-current 5V bias and can convert

from a 2.2V to 16V power rail. Both parts utilize a fixed-

frequency, voltage-mode, PWM control architecture and the

switching frequency is adjustable from 50kHz to 2MHz by

adjusting the value of an external resistor. Current limit is

achieved by monitoring the voltage drop across the on-

resistance of the low-side MOSFET, which enhances low

duty-cycle operation. The wide range of operating frequen-

cies gives the power supply designer the flexibility to fine-

tune component size, cost, noise and efficiency. The adap-

tive, non-overlapping MOSFET gate-drivers and high-side

bootstrap structure helps to further maximize efficiency. The

high-side power FET drain voltage can be from 2.2V to 16V

and the output voltage is adjustable down to 0.6V.

Typical Application

DS200494

Features

n Input power from 2.2V to 16V

n Output voltage adjustable down to 0.6V

n Power Good flag, adjustable soft-start and output enable

n Output over-voltage and under-voltage latch-off

n Output over-voltage and under-voltage flag (LM2737)

n Reference Accuracy: 1.5% (0˚C - 125˚C)

n Current limit without sense resistor

n Soft start

n Switching frequency from 50 kHz to 2 MHz

n TSSOP-14 package

Applications

n Cable Modems

n Set-Top Boxes/ Home Gateways

n DDR Core Power

n High-Efficiency Distributed Power

n Local Regulation of Core Power

for easy power sequencing

(LM2727)

20049410

www.national.com

June 2003

Related parts for BAT-54

BAT-54 Summary of contents

Page 1

... The high-side power FET drain voltage can be from 2.2V to 16V and the output voltage is adjustable down to 0.6V. Typical Application © 2003 National Semiconductor Corporation Features n Input power from 2.2V to 16V n Output voltage adjustable down to 0.6V n Power Good flag, adjustable soft-start and output enable ...

Page 2

Connection Diagram Pin Description BOOT (Pin 1) - Supply rail for the N-channel MOSFET gate drive. The voltage should be at least one gate threshold above the regulator input voltage to properly turn on the high-side N-FET. LG (Pin 2) ...

Page 3

Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications BOOTV Junction Temperature Storage Temperature Soldering Information Lead Temperature (soldering, 10sec) Electrical Characteristics unless ...

Page 4

Electrical Characteristics unless otherwise indicated. Typicals and limits appearing in plain type apply for T CC boldface type apply over full Operating Temperature Range. Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis. Symbol ...

Page 5

Typical Performance Characteristics Efficiency (V = 1.5V 300kHz 25˚ Operating Current vs Temperature 600kHz, No-Load SW Bootpin Current vs Temperature with 5V Bootstrap F = 600kHz, Si4826DY FET, No-Load ...

Page 6

Typical Performance Characteristics R vs PWM Frequency FADJ (in 100 to 800kHz range Operating Current Plus Boot Current vs CC PWM Frequency (Si4826DY FET, T Switch Waveforms (HG Rising 5V 1. ...

Page 7

Typical Performance Characteristics Start-Up (Full-Load 10V 1. 10A 10nF 300kHz SW Start Up (Full Load, 10x 10V 1. ...

Page 8

Typical Performance Characteristics Load Transient Response ( 12V 1. 300kHz SW Line Transient Response ( 1.2V 300kHz SW www.national.com (Continued ...

Page 9

Block Diagram Application Information THEORY OF OPERATION The LM2727 is a voltage-mode, high-speed synchronous buck regulator with a PWM control scheme designed for use in set-top boxes, thin clients, DSL/Cable modems, and other applications that require high efficiency ...

Page 10

Application Information MOSFET GATE DRIVERS The LM2727/37 has two gate drivers designed for driving N-channel MOSFETs in a synchronous mode. Power for the drivers is supplied through the BOOTV pin. For the high side gate (HG) to fully turn on ...

Page 11

Application Information DESIGN CONSIDERATIONS The following is a design procedure for all the components needed to create the circuit shown in Figure 3 in the Ex- ample Circuits section 1.2V out converter, capable of delivering 10A ...

Page 12

... BOOTV pin, this 0.1µF cap can be used to bypass the supply.) Using a Schottky device for the boot- strap diode allows the minimum drop for both high and low side drivers. The On Semiconductor BAT54 or MBR0520 work well standard pull-up resistor for the open-drain power good signal, and should be 10kΩ ...

Page 13

Application Information FET Conduction Loss P = 0.533W Cn Input Capacitor Loss 2 4.28 *0.018/2 = 0.084W Example Circuits This circuit and the one featured on the front page have been designed to deliver high current and high efficiency in ...

Page 14

Example Circuits (Continued) This circuit design, detailed in the Design Considerations section, uses inexpensive aluminum capacitors and off-the- shelf inductors. It can deliver 10A at better than 85% effi- ciency. Large bulk capacitance on input and output ensure stable operation. ...

Page 15

Example Circuits (Continued) The circuit of Figure 5 demonstrates the LM2727 delivering a low output voltage at high efficiency (87%) A separate 5V supply is required to run the chip, however the input voltage can be as low as 2.2 ...

Page 16

Example Circuits (Continued) FIGURE 6. 1.8V and 3.3V, 1A, 1.4MHz, Simultaneous The circuits in Figure 6 are intended for ADSL applications, where the high switching frequency keeps noise out of the data transmission range. In this design, the 1.8 and ...

Page 17

Example Circuits (Continued) FIGURE 7. 12V Unregulated to 3.3V, 3A, 750kHz This circuit shows the LM27x7 paired with a cost effective solution to provide the 5V chip power supply, using no extra components other than the LM78L05 regulator itself. The ...

Page 18

... Co3, Co4 Cc1 VJ1206A6R8KXX Cc2 VJ1206A271KXX Cc3 VJ1206A471KXX Rc2 CRCW12068451F Rfb1 CRCW12061102F ID Part Number U1 LM2727 Q1 Si4442DY Q2 Si4442DY D1 BAT-54 Lin SLF12575T-1R2N8R2 L1 D05022-152HC Cin1, Cin2 10MV5600AX Cinx C3216X7R1E105K Co1, Co2, 10MV5600AX Co3 Cboot VJ1206X104XXA Cin C3216X7R1E225K Css VJ1206X123KXX www.national.com Type Size Synchronous ...

Page 19

... CRCW12064222F Rc1 CRCW12065112F Rfb1 CRCW12062491F Rfb2 CRCW12064991F Rcs CRCW1206272J TABLE 5. Bill of Materials for Circuit of Figure 5 ID Part Number U1 LM2727 Q1 Si4884DY Q2 Si4884DY D1 BAT-54 Lin P1166.102T L1 P1168.102T Cin1 10MV5600AX Cinx C3216X7R1E105K Co1, Co2, 16MV4700WX Co3 Cboot VJ1206X104XXA Cin C3216X7R1E225K Css VJ1206X123KXX Type Size ...

Page 20

... VJ1206A4R7KXX Cc2 VJ1206A681KXX Rin CRCW1206100J Rfadj CRCW12064992F Rc1 CRCW12061473F Rfb1 CRCW12061492F Rfb2 CRCW12064991F Rcs CRCW1206332J ID Part Number U1 LM2727 Q1/Q2 Si4826DY D1 BAT-54 Lin RLF7030T-1R0N64 L1 RLF7030T-3R3M4R1 Cin1 C4532X5R1E156M Co1 C4532X5R1E156M Cboot VJ1206X104XXA Cin C3216X7R1E225K Css VJ1206X393KXX Cc1 VJ1206A220KXX Cc2 VJ1206A681KXX Cc3 VJ1206A681KXX Rin CRCW1206100J ...

Page 21

... TABLE 8. Bill of Materials for Circuit of Figure 7 (Continued) ID Part Number U2 LM78L05 Q1/Q2 Si4826DY D1 BAT-54 Lin RLF7030T-1R0N64 L1 SLF12565T-4R2N5R5 Cin1 16MV680WG Cinx C3216X5R1C106M Co1 Co2 16MV680WG Cox C3216X5R10J06M Cboot VJ1206X104XXA Cin C3216X7R1E225K Css VJ1206X123KXX Cc1 VJ1206A8R2KXX Cc2 VJ1206X102KXX Cc3 VJ1206X472KXX Rfadj CRCW12063252F Rc1 CRCW12065232F Rc2 ...

Page 22

... NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant ...

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