LT1776 Datasheet, PDF (6/20 Pages) Linear Technology – Wide Input Range, High Efficiency, Step-Down Switching Regulator

LT1776
PIN FUNCTIONS
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
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
V_CC 2
SHDN 1
BIAS
V_BG
V_B
SYNC 6
OSC
LOGIC
GND 4
V_C 8
FB 7
V_BG
BOOST
COMP
FB
V_TH
AMP
gm
5 V_IN
R1
R_SENSE
SWDR
SWDR
SWON
BOOST
SWOFF
I
COMP
SWON
I
Q3
Q4
Q2
Q1
D1
I
I
BOOST
I
SWOFF
Q5
3 V_SW
1776 BD
6