LTC3547
PI FU CTIO S
V
FB1
(Pin 1):
Regulator 1 Output Feedback. Receives
the feedback voltage from the external resistor divider
across the regulator 1 output. Nominal voltage for this
pin is 0.6V.
RUN1 (Pin 2):
Regulator 1 Enable. Forcing this pin to
V
IN
enables regulator 1, while forcing it to GND causes
regulator 1 to shut down.
V
IN
(Pin 3):
Main Power Supply. Must be closely decou-
pled to GND.
SW1 (Pin 4):
Regulator 1 Switch Node Connection to the
Inductor. This pin swings from V
IN
to GND.
GND (Pin 5):
Ground. Connect to the (–) terminal of C
OUT
,
and the (–) terminal of C
IN
.
SW2 (Pin 6):
Regulator 2 Switch Node Connection to
the Inductor. This pin swings from V
IN
to GND.
RUN2 (Pin 7):
Regulator 2 Enable. Forcing this pin to
V
IN
enables regulator 2, while forcing it to GND causes
regulator 2 to shut down.
V
FB2
(Pin 8):
Regulator 2 Output Feedback. Receives
the feedback voltage from the external resistor divider
across the regulator 2 output. Nominal voltage for this
pin is 0.6V.
Exposed Pad (Pin 9):
Electrically Connected to GND.
Must be soldered to the PCB for optimum thermal
performance.
FUNCTIONAL DIAGRAM
REGULATOR 1
BURST
CLAMP
SLOPE
COMP
3
V
IN
V
FB1
1
I
RCMP
SHUTDOWN
RUN1
RUN2
2
0.6V REF
7
OSC
OSC
SLEEP2
SLEEP1
V
FB2
8
REGULATOR 2 (IDENTICAL TO REGULATOR 1)
3547 FD
6
–
+
U
U
U
–
EA
0.6V
–
I
TH
V
SLEEP
SLEEP
–
I
COMP
+
5Ω
+
+
BURST
S
Q
RS
LATCH
R
Q
SWITCHING
LOGIC
AND
BLANKING
CIRCUIT
SOFT-START
ANTI
SHOOT-
THRU
4
SW1
5
GND
6
SW2
3547fa
LINEAR [ LINEAR INTEGRATED SYSTEMS ]
