SG6846C Ver la hoja de datos (PDF) - Fairchild Semiconductor

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Fabricante

SG6846C

Highly Integrated Green-Mode PWM Controller

Fairchild Semiconductor 

Marking Information

SG6846CFTP

XXXXXXXXYWWV

F: L = OCP Latch

T: D = DIP, S = SOP

P : Z = Lead Free +

ROHS Compatible

Null = regular package

XXXXXXXX: Wafer Lot

Y: Year; WW: Week

V: Assembly Location

Pin Configuration

Figure 3. Top Mark

GND

FB

VIN

RI

GATE

VDD

SENSE

RT

Figure 4. Pin Configuration

Pin Definitions

Pin # Name

1

GND

2

FB

3

VIN

4

RI

5

RT

6 SENSE

7

VDD

8 GATE

Function

Ground

Feedback

Line-voltage

Detection

Reference

Setting

Temperature

Detection

Current Sense

Power Supply

Driver Output

Description

Ground.

The signal from the external compensation circuit is fed into this pin. The

PWM duty cycle is determined in response to the signal from this pin and the

current-sense signal from pin 6.

Line-voltage detection, used for brownout protection with hysteresis. Constant

output power limit over universal AC input range is also achieved using this

pin. Add a low-pass filter to filter out line ripple on bulk capacitor.

A resistor from the RI pin to ground generates a reference current source that

determines the switching frequency. Increasing the resistance reduces the

switching frequency. Using a 26kΩ resistor results in a 65kHz switching

frequency.

For over-temperature protection, an external NTC thermistor is connected

from this pin to the GND pin. The impedance of the NTC decreases at high

temperatures. Once the voltage of the RT pin drops below a threshold, PWM

output is disabled.

Current sense. The sensed voltage is used for peak-current-mode control and

cycle-by-cycle current limiting. If the switching current is higher than OCP

threshold and lasts for 110ms, SG6846C turns off immediately. This two-level

OCP feature is especially suitable for SMPS with surge current output.

Power supply. If an open-circuit failure occurs in the feedback loop, the

internal protection circuit disables PWM output as long as VDD exceeds a

threshold.

The totem-pole output driver for the power MOSFET. It is internally clamped

below 18V.

© 2007 Fairchild Semiconductor Corporation

SG6846C • Rev. 1.1.2

3

www.fairchildsemi.com

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