LT1507
W
BLOCK DIAGRAM
0.1Ω
V
2
IN
+
–
CURRENT
SENSE
2.9V BIAS
REGULATOR
INTERNAL
CC
BIAS
AMPLIFIER
VOLTAGE GAIN = 5
V
BOOST
1
SLOPE COMP
Σ
0.9V
500kHz
OSCILLATOR
5
S
R
SYNC
Q1
POWER
SWITCH
R
DRIVER
CIRCUITRY
S
FLIP-FLOP
+
–
SHUTDOWN
COMPARATOR
V
3
SW
+
–
CURRENT
COMPARATOR
0.4V
FREQUENCY
SHIFT CIRCUIT
SHDN
4
3.5µA
FOLDBACK
CURRENT
LIMIT
Q2
+
–
CLAMP
–
7
6
FB/SENSE
LOCKOUT
COMPARATOR
+
ERROR
AMPLIFIER
= 2000µmho
2.38V
g
m
2.42V
8
V
C
GND
LT1507 • BD
Figure 1. Block Diagram
U
W U U
APPLICATIONS INFORMATION
Note: This application section is adapted from the more FEEDBACK PIN FUNCTIONS
complete version found in the LT1375/LT1376 data sheet.
The feedback pin (FB or SENSE) on the LT1507 is used to
set output voltage and also to provide several overload
protection features. The first part of this section deals with
selecting resistors to set output voltage and the remaining
part talks about foldback frequency and current limiting
created by the FB pin. Please read both parts before
If more details are desired consult the LT1375/LT1376
Applications Information section, but please acquaint
yourself thoroughly with this LT1507 information first so
that differences between the LT1375 and the LT1507 do
not cause confusion.
7
Linear [ Linear ]
