SC4812 データシートの表示（PDF） - Semtech Corporation

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SC4812

Current Mode PWM Controller with Integrated Start-up Circuit and Op Amp

Semtech Corporation 

SC4812

POWER MANAGEMENT

Pin Descriptions

Pin #

1

2

3

4

5

6

7

8

Pin Name

VIN

FB

COMP

SS/SHDN

CS

GND

OUT

VCC

Pin Function

High voltage startup input. Connect directly to an input voltage between 12 to 90V. Connects

internally to a high voltage linear regulator that generates VCC during startup.

Feedback input to the internal transconductance error amplifier. VFB sensed the regulated

output voltage through an external resistor divider.

Internal transconductance error amplifier output. Compensation network of the overall loop is

placed between this pin and GND.

Soft start timing capacitor connection. Ramp time to full current limit is approximately TBD

ms/nF. This pin is also the reference voltage output. Bypass with a minimum 10nF capacitor

to GND. The device goes into shutdown when VSS_SHDN is pulled below 0.25V.

Current sense input. Turns power switch off if VCS rises above 465mV for cycle-by-cycle

current limiting. CS is also the feedback for the current mode controller. CS is connected to

the PWM comparator through a leading edge blanking circuit.

Ground.

Gate drive. Drives a high voltage external N-channel power MOSFET.

Supply voltage. Provides power for entire IC. VCC is regulated from VIN during startup. Bypass

VCC with a 10uF tantalum capacitor in parallel with 0.1uF ceramic capacitor to GND.

 2007 Semtech Corp.

5

www.semtech.com

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