LT1308A/LT1308B
BLOCK DIAGRA S
V
IN
V
IN
6
R5
40k
R6
40k
V
IN
Q4
2V
BE
SHDN
V
OUT
R1
(EXTERNAL)
FB
R2
(EXTERNAL)
FB
2
R4
140k
RAMP
GENERATOR
600kHz
OSCILLATOR
*HYSTERESIS IN LT1308A ONLY
Figure 2a. LT1308A/LT1308B Block Diagram (SO-8 Package)
V
IN
Q4
2V
BE
SHDN
V
IN
11
V
IN
12
R5
40k
R6
40k
V
IN
+
g
m
V
C
1
LBI
ERROR
AMPLIFIER
BIAS
V
OUT
R1
(EXTERNAL)
FB
R2
(EXTERNAL)
–
FB
2
Q1
Q2
×10
R3
30k
R4
140k
RAMP
GENERATOR
+
*
ENABLE
200mV
–
COMPARATOR
FF
R
Q
S
DRIVER
600kHz
OSCILLATOR
*HYSTERESIS IN LT1308A ONLY
Figure 2b. LT1308A/LT1308B Block Diagram (TSSOP Package)
+
+
Σ
+
+
+
Σ
+
–
–
W
Q1
+
g
m
V
C
1
LBI
ERROR
AMPLIFIER
BIAS
SHUTDOWN
3
–
Q2
×10
R3
30k
+
*
ENABLE
200mV
7
+
–
A4
LBO
8
–
A1
COMPARATOR
SW
FF
R
Q
S
DRIVER
5
Q3
A2
+
A=3
0.03Ω
–
4
GND
1308 BD2a
SHUTDOWN
3
13
+
–
A4
LBO
14
SW SW SW
8
9
10
A1
Q3
A2
+
A=3
0.03Ω
–
4
5
6
7
1308 BD2b
GND GND GND GND
1308abfa
7
LINER [ LINEAR TECHNOLOGY ]
