Datasheet

6
LT1776
10% and 90% duty cycle. The sync function is internally
disabled if the FB pin voltage is low enough to cause
oscillator slowdown. If unused, this pin should be grounded.
FB (Pin 7): This is the inverting input to the feedback
amplifier. The noninverting input of this amplifier is inter-
nally tied to the 1.24V reference. This pin also slows down
the frequency of the internal oscillator when its voltage is
PIN FUNCTIONS
UUU
abnormally low, e.g., 2/3 of normal or less. This feature
helps maintain proper short-circuit protection.
V
C
(Pin 8): This is the control voltage pin which is the
output of the feedback amplifier and the input of the
current comparator. Frequency compensation of the over-
all loop is effected by placing a capacitor, (or in most cases
a series RC combination) between this node and ground.
BLOCK DIAGRA
W
SWDR
SWDR
SWON
SWON
BOOST
1776 BD
BOOST
SWOFF
SWOFF
LOGICOSC
BIAS
V
TH
V
B
V
BG
V
BG
FB
V
C
GND
SYNC
SHDN
V
CC
FB
AMP
BOOST
COMP
gm
I
I
I I
R1 R
SENSE
I
COMP
Q4
Q3
Q2
Q1
Q5
V
SW
D1
V
IN
5
3
2
1
6
4
8
7