LTC3520 Datasheet, PDF (21/24 Pages) Linear Technology – Synchronous 1A Buck-Boost and 600mA Buck Converters

TYPICAL APPLICATIONS
Sequenced Buck Converter Start-Up
3.3V at 500mA and 1.8V at 600mA Outputs
LTC3520
V_OUT
1.8V
600mA
V_IN
2.2V TO 4.2V
Li-Ion
255k
C2
22µF
200k
PWM
BURST
C1
22µF
L2
3.3µH
PV_IN1 PV_IN2 PV_IN3 SV_IN SW1A
SW1B
SW2
V_OUT1
27pF
V_C1
FB2
0.022µF
SS2
FB1
54.9k
R_T
PWM1
301k
PWM2
LTC3520
SS1
A_IN
A_OUT
L1
4.7µH
470pF
15k
0.022µF
SD3
ON
OFF
SD1
SD2
PGND1 SGND PGND2
56pF
1M
10k
309k
C3
22µF
V_OUT
3.3V
500mA
1A FOR V_IN ≥ 3V
442k
158k
470pF
499k
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.
3520 TA02a
Typical Waveforms During Power-Up
SD1, SD3
5V/DIV
BUCK-BOOST
V_OUT
2V/DIV
A_OUT
5V/DIV
BUCK V_OUT
1V/DIV
1ms/DIV
3520 TA02b
3520f
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