SG6846G Просмотр технического описания (PDF) - Fairchild Semiconductor
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SG6846G Datasheet PDF : 14 Pages
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Marking Information
Pin Configuration
: Fairchild Logo
Z: Plant Code
X: Year Code
Y: Week Code
TT: Die Run Code
F: L = OCP Latch
T: Package Type, S = SOP
P: Y = Green Compound
M: Manufacturing Flow Code
Figure 3. Top Mark
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 is 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 the 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 500ms, SG6846G 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.
© 2008 Fairchild Semiconductor Corporation
SG6846G • Rev. 1.0.2
3
www.fairchildsemi.com
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