Datasheet

8
LT1738
1738fa
V
C
(Pin 12): The compensation pin is used for frequency
compensation and current limiting. It is the output of the
error amplifier and the input of the current comparator.
Loop frequency compensation can be performed with an
RC network connected from the V
C
pin to ground. The
voltage on V
C
is proportional to the switch peak current.
The normal range of voltage on this pin is 0.25V to 1.27V.
However, during slope compensation the upper clamp
voltage is allowed to increase with the compensation.
During a short-circuit fault the V
C
pin will be discharged to
ground.
PI FU CTIO S
UUU
BLOCK DIAGRA
W
Figure 1a. Typical Test Circuitry
+
V
C
NFB
FB
1738 BD
SS
SLEW
CONTROL
V
REG
V
IN
V5
TO
DRIVERS
SQ
FF
R
OSCILLATOR
–
+
NEGATIVE
FEEDBACK
AMP
+
–
+
–
ERROR
AMP
1.25V
100k 50k
COMP
–
+
SENSE
AMP
SHDN R
VSL
R
CSL
REGULATOR
R
T
C
T
CAP
GATE
GCL
PGND
SYNC GND
SUB
CS
4
116
7
8
13
9
10
14 17 5 15
16
12
20
1
2
3
Figure 1b. Test Circuit for Slew
+
–
5pF
IN5819
20mA
2
1738 F01a
ZVN3306A
10
GATE
CAP
+
–
5pF
IN5819
0.9A
0.1
1738 F01b
Si4450DY
10
GATE
CS
CAP
TEST CIRCUITS