THV3056_Rev.2.00_E
85%
85%
VGH/VGL
Latch Voltage=1.2V
SCP
SCP Latch Time >> VGH/VGL Startup Time
Figure 11. Charge Pump SCP Operation Waveform
● Over Voltage Protection(OVP)
OVP circuit stops the output, if the output voltage on ch-1/2/3 exceed the predetermined voltage. The internal OVP
comparator (with reference voltage of 1.5V for ch-1 and ch-3, 1.06V for ch-3) monitors the voltage on INV pins. The
output of OVP comparator is connected to OUT pin. When the voltage on INV pin exceeds 1.5V for ch-1 and ch-3,
1.06V for ch-2, OUT pin turns external MOS transistor Off and stops switching operation to prevent the output voltage
excessing the predetermined voltage.(See Figure 12.) Also, OVP comparator of ch-2 and ch-3 report the abnormal
operation to SCP circuit.
Vout
FB
Rh
Error AMP
PWM COMP
-
OUT
+
INV
100uA
VREF
OVP COMP
-
+
ch1, ch-3=1.5V
ch-2=1.06V
Figure 12. OVP Circuit
Note) Operation at FB - INV short circuit
ꢀWhen FB pin and INV pin are short circuited, the internal constant current circuit (100uA) affects the output voltage.
An approximate output voltage is given by the following formula.
ꢀThe output voltage at FB-INV short circuited(Vout) = the normal output voltage x 1.25 + Rh x 100uA
Also, OVP comparator has Delay circuit of 0.5us to prevent the malfunction, so the actual output voltage will be higher
than the result of calculation.
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THine Electronics, Inc.
Copyright©2010 THine Electronics, Inc.
THINE [ THINE ELECTRONICS, INC. ]
