Datasheet

LTC3520
21
3520fa
TYPICAL APPLICATIONS
Sequenced Buck Converter Start-Up
3.3V at 500mA and 1.8V at 600mA Outputs
3520 TA02a
SW1A
SW1B
V
OUT1
A
OUT
A
IN
V
C1
FB1
SS1
SV
IN
PV
IN3
PV
IN2
PV
IN1
PGND2SGNDPGND1
SW2
FB2
SS2
R
T
PWM1
PWM2
SD3
SD1
SD2
C3
22μF
1M
442k
309k
15k
470pF
10k
56pF
LTC3520
V
OUT
3.3V
500mA
1A FOR V
IN
≥ 3V
V
OUT
1.8V
600mA
V
IN
2.2V TO 4.2V
C1, C2, C3: TAIYO YUDEN CERAMIC JMK212BJ226MG-T
L1: TDK RLF7030T-4R7M3R4 4.7μH
L2: TDK RLF7030T-3R3M4R 3.3μH
THE BUCK CONVERTER IS ENABLED WHEN THE
BUCK-BOOST OUTPUT VOLTAGE REACHES 3.0V.
C2
22μF
470pF
0.022μF
0.022μF
54.9k
255k
200k
301k
499k
C1
22μF
Li-Ion
L2
3.3μH
L1
4.7μH
158k
27pF
PWM
BURST
ON
OFF
Typical Waveforms During Power-Up
SD1, SD3
5V/DIV
1ms/DIV
BUCK V
OUT
1V/DIV
BUCK-BOOST
V
OUT
2V/DIV
A
OUT
5V/DIV
3520 TA02b