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ERROR AMP CONFIGURATION
_
+
2.5 V
2
1
V
FB
COMP
Z
F
Z
I
0.5 mA
UNDER-VOLTAGE LOCKOUT
V
CC
<17 mA
<1 mA
V
OFF
V
ON
V
CC
7
V
CC
ON/OFF Command
to REST of IC
UC1842
UC1844
UC1843
UC1845
V
ON
V
OFF
16 V
10 V
8.4 V
7.6 V
CURRENT SENSE CIRCUIT
Peak Current (I
S
) is Determined By The Formula
ERROR
AMP
2R
R
1 V
5
COMP
CURRENT
SENSE
GND
I
S
R
C
R
S
CURRENT
SENSE
COMPARATOR
,1.0 V
RS
I
SMAX
1
3
5
UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5
SLUS223C – APRIL 1997 – REVISED JUNE 2007
Error amp can source or sink up to 0.5 mA.
During under-voltage lock-out, the output drive is biased to sink minor amounts of current. Pin 6 should be
shunted to ground with a bleeder resistor to prevent activating the power switch with extraneous leakage
currents.
A small RC filter may be required to suppress switch transients.
5
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