LTC3548
5
3548fc
V
FB1
(Pin 1): Output Feedback. Receives the feedback
voltage from the external resistive divider across the
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. This pin must be driven; do not fl oat.
V
IN
(Pin 3): Main Power Supply. Must be closely decoupled
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. This pin is not connected internally.
Connect to PCB ground for optimum shielding.
MODE/SYNC (Pin 6): Combination Mode Selection and
Oscillator Synchronization. This pin controls the operation
of the device. When tied to V
IN
or GND, Burst Mode
operation or pulse-skipping mode is selected, respectively.
Do not fl oat this pin. The oscillation frequency can be
synchronized to an external oscillator applied to this pin
and pulse-skipping mode is automatically selected.
SW2 (Pin 7): Regulator 2 Switch Node Connection to the
Inductor. This pin swings from V
IN
to GND.
POR (Pin 8): Power-On Reset . This common-drain logic
output is pulled to GND when the output voltage falls
below –8.5% of regulation and goes high after 117ms
when both channels are within regulation.
RUN2 (Pin 9): Regulator 2 Enable. Forcing this pin to V
IN
enables regulator 2, while forcing it to GND causes regulator
2 to shut down. This pin must be driven; do not fl oat.
V
FB2
(Pin 10): Output Feedback. Receives the feedback
voltage from the external resistive divider across the output.
Nominal voltage for this pin is 0.6V.
Exposed Pad (GND) (Pin 11): Power Ground. Connect to
the (–) terminal of C
OUT
, and (–) terminal of C
IN
. Must be
connected to electrical ground on PCB.
PIN FUNCTIONS
TYPICAL PERFORMANCE CHARACTERISTICS
Effi ciency vs Load Current
Effi ciency vs Load Current Effi ciency vs Load Current
T
A
= 25°C unless otherwise specifi ed.
LOAD CURRENT (mA)
1
EFFICIENCY (%)
100
90
80
70
60
50
40
10 100 1000
3548 G10
3.6V
2.7V
4.2V
V
OUT
= 2.5V, CHANNEL 1
Burst Mode OPERATION
NO LOAD ON OTHER CHANNEL
CIRCUIT OF FIGURE 3
LOAD CURRENT (mA)
1
EFFICIENCY (%)
100
95
90
85
80
75
70
65
60
10 100 1000
3548 G14
2.7V
4.2V
V
OUT
= 1.5V, CHANNEL 1
Burst Mode OPERATION
NO LOAD ON OTHER CHANNEL
CIRCUIT OF FIGURE 3
3.6V
LOAD CURRENT (mA)
1
EFFICIENCY (%)
100
95
90
85
80
75
70
65
60
10 100 1000
3548 G13
2.7V
4.2V
V
OUT
= 1.2V, CHANNEL 1
Burst Mode OPERATION
NO LOAD ON OTHER CHANNEL
CIRCUIT OF FIGURE 3
3.6V