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| SM8122A Datasheet, PDF (6/13 Pages) Nippon Precision Circuits Inc – White LED Driver IC | |||
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SM8122A
OVP (Over Voltage Protection)
SM8122A is always monitoring the VOUT terminal voltage in order to protect itself from the stress of VOUT
over voltage. If SM8122A detects the VOUT over voltage, it immediately stop the switching of the inductor
drive transistor. After the VOUT terminal voltage decreases below the release voltage, SM8122A restarts
switching the inductor drive transistor. The over voltage is set as approximately 30.5V, the release voltage is
approximately 28.5V.
30.5V
28.5V
Over voltage
detection
Over voltage
detection
Over voltage
detection release
Over voltage
detection release
SW Tr = OFF
SW Tr
Switching
SW Tr = OFF
Selecting the Current-setting Resistor (R1)
The SM8122A control stabilizes the voltage on pin FB (0.5V typ.). Hence, the current-setting resistor R1 con-
nected between FB and VSS sets the LED current ILED, where the resistance R1 is given by the following
equation.
R1 = 0.5 / ILED
FB VFB=0.5V
ILED=0.5/R1
R1=0.5/ILED
NIPPON PRECISION CIRCUITS INC.â6
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