Datasheet

5
LT1610
PIN FUNCTIONS
UUU
V
C
(Pin 1): Error Amplifier Output. Frequency compensa-
tion network must be connected to this pin, either internal
(COMP pin) or external series RC to ground. 220kΩ/
220pF typical value.
FB (Pin 2): Feedback Pin. Reference voltage is 1.23V.
Connect resistive divider tap here. Minimize trace area at
FB. Set V
OUT
according to V
OUT
= 1.23V (1 + R1/R2).
SHDN (Pin 3): Shutdown. Ground this pin to turn off
device. Tie to 1V or more to enable.
PGND (Pin 4): Power Ground. Tie directly to local ground
plane.
SW (Pin 5): Switch Pin. Connect inductor/diode here.
Minimize trace area at this pin to keep EMI down.
V
IN
(Pin 6): Input Supply Pin. Must be locally bypassed.
GND (Pin 7): Signal Ground. Carries all device ground
current except switch current. Tie to local ground plane.
COMP (Pin 8): Internal Compensation Network. Tie to V
C
pin, or let float if external compensation is used. Output
capacitor must be tantalum if COMP pin is used for com-
pensation.
BLOCK DIAGRA
W
FB
FB
BIAS
V
C
R5
40k
1.7MHz
OSCILLATOR
RAMP
GENERATOR
FF
S
RQ
0.15Ω
V
IN
V
IN
–
+
–
+
COMP
4
7
3
8
5
6
1
–
+
A = 3
V
OUT
SW
GND
Q1
Q2
× 10
Q3
PGND
A2
1610 F02
SHDNSHUTDOWN
ENABLE
COMPARATOR
DRIVER
R6
40k
R3
30k
R2
(EXTERNAL)
R
C
C
C
R4
140k
R1
(EXTERNAL)
–
+
A1
g
m
2
Σ
Figure 2. LT1610 Block Diagram