LTC3528/LTC3528B
6
3528fd
PIN FUNCTIONS
Load Step Response (Fixed
Frequency, 1.2V to 3.3V)
Load Step Response (Burst Mode
Operation, 1.2V to 3.3V, LTC3528)
SHDN (Pin 1): Logic Controlled Shutdown Input. There is
an internal 4MΩ pull-down resistor on this pin.
•SHDN = High: Normal operation
•SHDN = Low: Shutdown, quiescent current < 1µA
FB (Pin 2): Feedback Input. Connect resistor divider tap
to this pin. The output voltage can be adjusted from 1.6V
to 5.25V by:
V
OUT
= 1.20V • 1+
R2
R1
PGOOD (Pin 3): Power Good Comparator Output. This
open-drain output is low when V
FB
< 10% from its regu-
lation voltage.
V
OUT
(Pin 4): Output Voltage Sense and Drain Connection
of the Internal Synchronous Rectifier. PCB trace length
from V
OUT
to the output filter capacitor (4.7µF minimum)
should be as short and wide as possible.
SW (Pin 5): Switch Pin. Connect inductor between SW
and V
IN
. Keep PCB trace lengths as short and wide as
possible to reduce EMI. If the inductor current falls to
zero, or SHDN is low, an internal anti-ringing switch is
connected from SW to V
IN
to minimize EMI.
PGND (Pin 6): Power Ground. Provide a short direct PCB
path between PGND and the (–) side of the input and
output capacitors.
Load Step Response (Fixed
Frequency, 3.6V to 5V)
Load Step Response (Burst Mode
Operation, 3.6V to 5V, LTC3528)
V
OUT
and I
IN
During Soft-Start
Burst Mode Waveforms
5µs/DIV
3528 G20
V
IN
= 3.6V
V
OUT
= 5V
C
OUT
= 22µF
C
FF
= 33pF
I
LOAD
= 30mA
V
OUT
20mV/DIV
INDUCTOR
CURRENT
100mA/DIV
V
OUT
1V/DIV
SHDN PIN
200µs/DIV
3528 G21
V
IN
= 1.2V
V
OUT
= 3.3V
C
OUT
= 10µF
L = 4.7µH
I
IN
200mA/DIV
V
OUT
100mV/DIV
20µs/DIV
3528 G22
V
IN
= 3.6V
V
OUT
= 5V
C
OUT
= 10µF
L = 4.7µH
LOAD
CURRENT
200mA/DIV
V
OUT
100mV/DIV
50µs/DIV
3528 G23
V
IN
= 3.6V
V
OUT
= 5V
C
OUT
= 10µF
L = 4.7µH
LOAD
CURRENT
200mA/DIV
V
OUT
100mV/DIV
50µs/DIV
3528 G24
V
IN
= 1.2V
V
OUT
= 3.3V
C
OUT
= 10µF
L = 4.7µH
LOAD
CURRENT
100mA/DIV
V
OUT
100mV/DIV
50µs/DIV
3528 G25
V
IN
= 1.2V
V
OUT
= 3.3V
C
OUT
= 10µF
L = 4.7µH
LOAD
CURRENT
100mA/DIV
TYPICAL PERFORMANCE CHARACTERISTICS
(T
A
= 25°C unless otherwise noted)