NCP1547(2007) 데이터 시트보기 (PDF) - ON Semiconductor

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NCP1547
(Rev.:2007)

1.5 A, 340 kHz, Buck Regulator with Synchronization Capability

ON Semiconductor 

NCP1547

PACKAGE PIN DESCRIPTION

PIN NO.

PIN SYMBOL

FUNCTION

1

BOOST

The BOOST pin provides additional drive voltage to the on−chip NPN power transistor. The

resulting decrease in switch on voltage increases efficiency.

2

VIN

This pin is the main power input to the IC.

3

VSW

This is the connection to the emitter of the on−chip NPN power transistor and serves as the

switch output to the inductor. This pin may be subjected to negative voltages during switch off−

time. A catch diode is required to clamp the pin voltage in normal operation. This node can

stand −1.0 V for less than 50 ns during switch node flyback.

4

SHDNB

The shutdown pin is active low and TTL compatible. The IC goes into sleep mode, drawing less

than 1.0 mA when the pin voltage is pulled below 1.0 V.

This pin should be left floating in normal position.

5

SYNC

This pin provides the synchronization input.

6

GND

Power return connection for the IC.

7

VFB

The FB pin provides input to the inverting input of the error amplifier. If VFB is lower than 0.29 V,

the oscillator frequency is divided by four, and current limit folds back to about 1 A. These fea-

tures protect the IC under severe overcurrent or short circuit conditions.

8

VC

The VC pin provides a connection point to the output of the error amplifier and input to the PWM

comparator. Driving of this pin should be avoided because on−chip test circuitry becomes active

whenever current exceeding 0.5 mA is forced into the IC.

9, 11, 12, 14, 15, 18

NC

No Connection

PIN CONNECTIONS

BOOST 1

VIN

2

VIN

3

VIN

4

Vsw 5

VSW

6

VSW

7

SHDNB 8

NC 9

18 NC

17 VC

16

VFB

15 NC

14 NC

13 GND

12 NC

11 NC

10 SYNC

18−Lead DFN

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