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| LTC3521 Datasheet, PDF (6/20 Pages) Linear Technology – Wide VIN, 1A Buck-Boost DC/DC and Dual 600mA Buck DC/DC Converters | |||
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LTC3521
Typical Performance Characteristics TA = 25°C, unless otherwise noted.
Buck-Boost Burst to
PWM Transition
Buck Load Step, PWM Mode,
10mA to 400mA
Buck Load Step, Burst Mode
Operation, 10mA to 400mA
INDUCTOR
CURRENT
200mA/DIV
VOUT
100mV/DIV
VOUT
100mV/DIV
VOUT
20mV/DIV
50µs/DIV
VIN = 3.6V L = 4.7µH
VOUT = 3.3V COUT = 22µF
INDUCTOR
CURRENT
200mA/DIV
3521 G16
VIN = 3.6V
VOUT = 1.8V
100µs/DIV
L = 4.7µH
COUT = 10µF
INDUCTOR
CURRENT
200mA/DIV
3521 G17
VIN = 3.6V
VOUT = 1.8V
100µs/DIV
L = 4.7µH
COUT = 10µF
3521 G18
Buck-Boost Current Limit
vs Temperature
2150
Buck-Boost Peak Current Limit
vs Temperature
3350
Buck Current Limit
vs Temperature
1150
2100
2050
2000
3300
3250
1100
1050
1000
950
1950
â50 â25
0 25 50 75
TEMPERATURE (°C)
100 125
3521 G19
3200
â50 â25
0 25 50 75
TEMPERATURE (°C)
100 125
3521 G20
900
â50 â25
0 25 50 75
TEMPERATURE (°C)
100 125
3521 G21
Pin Functions (FE/UF Packages)
FB3 (Pin 1/Pin 23): Feedback Voltage for the Buck Con-
verter Derived from a Resistor Divider Connected to the
Buck VOUT3 Output Voltage. The buck output voltage is
given by the following equation, where R1 is a resistor
between FB3 and ground, and R2 is a resistor between
FB3 and the buck output voltage:
VOUT3
=
0.6V ï£ï£¬1+
R2
R1
FB2 (Pin 2/Pin 24): Feedback Voltage for the Buck Con-
verter Derived from a Resistor Divider Connected to the
Buck VOUT2 Output Voltage. The buck output voltage is
given by the following equation, where R1 is a resistor
between FB2 and ground, and R2 is a resistor between
FB2 and the buck output voltage:
VOUT2
=
0.6V
ï£ï£¬1+
R2
R1
SHDN2 (Pin 3/Pin 1): Forcing this pin above 1.4V enables
the buck converter output at SW2. Forcing this pin below
0.4V disables the buck converter. This pin cannot be left
floating.
PGOOD3 (Pin 4/Pin 2): This pin is an open-drain output
which pulls low under any of the following conditions:
VOUT3 buck output voltage is out of regulation, the part is
3521f
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