SG6859A Fairchild Semiconductor, SG6859A Datasheet - Page 4

• Manufacturer Part Number: SG6859A
• Description: This highly integrated PWM controller provides several special enhancements designed to meet the low standby-power needs of low-power SMPS
• Manufacturer: Fairchild Semiconductor

© 2007 Fairchild Semiconductor Corporation
SG6859A • Rev. 1.0.4
Pin Configurations
Pin Definitions
Pin #
DIP
1
2
3
4
5
6
7
8
Figure 4. SSOT-6 Pin Configuration
SSOT
Pin #
6
5
4
3
2
1
SENSE
Name
GATE
GND
VDD
NC
NC
FB
RI
Description
The totem-pole output driver for driving the power MOSFET.
Power supply
No connection
Current sense. This pin senses the voltage across a resistor. When the voltage
reaches the internal threshold, PWM output is disabled. This activates over-current
protection. This pin also provides current amplitude information for current-mode
control.
A resistor connected from the RI pin to ground generates a constant current source
used to charge an internal capacitor and determine the switching frequency.
Increasing the resistance reduces the amplitude of the current source and the
switching frequency. A 95kΩ resistor R
70kHz switching frequency.
No connection
Feedback. The FB pin provides the output voltage regulation signal. It provides
feedback to the internal PWM comparator, so that the PWM comparator can control
the duty cycle.
Ground
4
I
Figure 5. DIP-8 Pin Configuration
results in a 50μA constant current I
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I
and a