LTC3523-2_15 Datasheet, PDF (12/16 Pages) Linear Technology – Synchronous 600mA Step-Up and 400mA Step-Down DC/DC Converters

LTC3523/LTC3523-2
APPLICATIONS INFORMATION
DUAL BUCK-BOOST AND STEP-UP CONVERTER
OPERATION
The LTC3523/LTC3523-2 can be operated in a cascaded
configuration as shown in Figure 2, allowing buck-boost
and step-up converter operation. Supply rail sequencing
is achieved by feeding the step-up converter PGOOD1
into the step-down’s SHDN2 pin. Note that the overall
3.3V converter efficiency is the product of the individual
efficiencies.
V_IN
1.8V TO 5.25V
V_OUT1
STEP-UP
OUTPUT
5V
100mA
4.7μF
10μH
V_IN1 V_IN2 V_BAT
SW1
SW2
4.7μH
10μF ^768k
243k
V_{OUT LTC3523}
FB2
FB1
MODE V_IN
PGOOD1
PGOOD2
SHDN1
SHDN2
GND1 GND2 GND3
10pF 825k
182k
V_OUT2
STEP-DOWN
OUTPUT
10μF
3.3V
50mA
OFF ON
100k
V_IN
3523 F02a
100
90
80
70
60
50
40
30
20
10
0
0.1
5V OUTPUT
3.3V OUTPUT
V_IN = 2.4V
V_OUT1 = 5V
V_OUT2 = 3.3V
f_OSC = 1.2MHz
BURST ENABLED
1
10
100
OUTPUT CURRENT (mA)
1000
3523 F02b
Figure 2. Dual Converter Efficiency (Load Applied
to Step-Down Output)
3523fb
12