ltc3521fe Linear Technology Corporation, ltc3521fe Datasheet - Page 6

• Manufacturer Part Number: ltc3521fe
• Description: Ltc3521 Wide Vin, 1a Buck-boost Dc/dc And Dual 600ma Buck Dc/dc Converters Features
• Manufacturer: Linear Technology Corporation

200mA/DIV
LTC3521
Typical perForMance characTerisTics
FB3 (Pin 1/Pin 23): Feedback Voltage for the Buck Con-
verter Derived from a Resistor Divider Connected to the
Buck V
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:
FB2 (Pin 2/Pin 24): Feedback Voltage for the Buck Con-
verter Derived from a Resistor Divider Connected to the
Buck V
INDUCTOR
pin FuncTions

CURRENT
20mV/DIV
V
2150
2100
2050
2000
1950
V
OUT3
OUT
–50
OUT3
OUT2
Buck-Boost Current Limit
vs Temperature
Buck-Boost Burst to
PWM Transition
V
V
IN
OUT
=
= 3.6V
–25
= 3.3V
0 6
.
Output Voltage. The buck output voltage is
Output Voltage. The buck output voltage is
V
0
TEMPERATURE (°C)

 
L = 4.7µH
C
1
OUT
+
50µs/DIV
25
= 22µF
R
R
2
1

 
50
(FE/UF Packages)
75
100
3521 G16
3521 G19
125
100mV/DIV
200mA/DIV
INDUCTOR
CURRENT
3350
3300
3250
3200
V
OUT
–50
Buck Load Step, PWM Mode,
10mA to 400mA
Buck-Boost Peak Current Limit
vs Temperature
V
V
IN
OUT
= 3.6V
–25
= 1.8V
0
TEMPERATURE (°C)
L = 4.7µH
C
OUT
100µs/DIV
25
= 10µF
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:
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:
V
OUT3
50
V
OUT2
buck output voltage is out of regulation, the part is
75
=
100
T
0 6
A
.
3521 G17
= 25°C, unless otherwise noted.
3521 G20
V
125

 
1
+
100mV/DIV
200mA/DIV
INDUCTOR
CURRENT
R
R
2
1
1150
1050
1000
1100
V
950
900

 
OUT
–50
Buck Load Step, Burst Mode
Operation, 10mA to 400mA
Buck Current Limit
vs Temperature
V
V
IN
OUT
= 3.6V
–25
= 1.8V
0
TEMPERATURE (°C)
L = 4.7µH
C
OUT
100µs/DIV
25
= 10µF
50
75
100
3521 G18
3521f
3521 G21
125