ML4903 Просмотр технического описания (PDF) - Micro Linear Corporation

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ML4903

High Current Synchronous Buck Controller

Micro Linear Corporation 

ML4903

FUNCTIONAL DESCRIPTION (Continued)

UNDERVOLTAGE LOCKOUT

The ML4903 has hysteretic undervoltage lockout

protection circuits for both the 12V (VDD) and 5V (VCC)

supplies. During an input undervoltage condition, the

internal reference and voltage monitor circuits remain in

operation, but P DRV and N DRV are disabled and the

PWR GOOD output will be false (low).

COMPENSATION

The COMP pin is connected to the output of the

transconductance amplifier which forms the gain block

for the proportional control loop of the ML4903. An RC

network from this pin to GND is used to compensate the

amplifier.

12VIN

R6

10Ω

C20

22µF

25V

5VIN

VID0

VID1

VID2

VID3

VID4

OUTEN

PWRGD

C22

1nF

C14

220nF

16V

C10

L1

220nF

16V

C12

220nF

R3

1MΩ

1µH

16V

1

D0

20

PROTECT

2

D1

3

D2

4

D3

19

VDD

18

VCC

17

P DRV

5

RANGE

16

N DRV

6 SHDN

15

PWR GND

7

N/C

14

N/C

8

PWR GOOD

13

COMP

9

VREF

10

GND

12

ISENSE

11

VFB

U1

ML4903

R2

1kΩ

C1 C2 C3

C11

220nF

16V

Q1, Q2

2X IRF7416

Q3, Q4

2X IRF7413

L2

5.6µH

R1

33Ω

C4-C9

VCCP

R4

470kΩ

C13

1nF

R5

100Ω

VSS

C1 - C3 - 820µF, 16V, Sanyo 16MV820GX

C4 - C9 - 1500µF, 6.3V, Sanyo 6MV1500GX

Figure 1. Typical VRM Circuit

6

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