LTC3521
3
3521fb
For more information www.linear.com/LTC3521
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC3521 is tested under pulsed load conditions such that
T
J
≈
T
A
. The LTC3521E is guaranteed to meet performance specifica-
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Voltage
l
1.8 5.5 V
Quiescent Current—Shutdown V
SHDN1
= V
SHDN2
= V
SHDN3
= 0V (Note 6)
l
0.01 2 µA
Burst Mode Quiescent Current V
FB1
= 0.66V, V
FB2
= 0.66V, V
FB3
= 0.66V, V
PWM
= 0V 30 µA
Oscillator Frequency
l
0.85 1.1 1.35 MHz
SHDN1, SHDN2, SHDN3, PWM Input High Voltage
l
1.4 V
SHDN1, SHDN2, SHDN3, PWM Input Low Voltage
l
0.4 V
Power Good Outputs Low Voltage I
PGOOD1
= I
PGOOD2
= I
PGOOD3
= 1mA 0.1 0.2 V
Power Good Outputs Leakage Current V
PGOOD1
= V
PGOOD2
= V
PGOOD3
= 5.5V 0.1 10 µA
Buck Converters
PMOS Switch Resistance 0.205 Ω
NMOS Switch Resistance 0.170 Ω
NMOS Switch Leakage Current V
SW2
= V
SW3
= 5.5V, V
IN
= 5.5V 0.1 5 µA
PMOS Switch Leakage Current V
SW2
= V
SW3
= 0V, V
IN
= 5.5V 0.1 10 µA
Feedback Voltage (Note 4)
l
0.585 0.6 0.612 V
Feedback Input Current V
FB2
= V
FB3
= 0.6V 1 50 nA
PMOS Current Limit (Note 3)
l
750 1050 mA
Maximum Duty Cycle V
FB2
= V
FB3
= 0.55V
l
100 %
Minimum Duty Cycle V
FB2
= V
FB3
= 0.66V
l
0 %
PGOOD Threshold V
FB2,3
Falling –12 –9 –6 %
Power Good Hysteresis V
FB2,3
Returning Good 2 %
Buck-Boost Converter
Output Voltage
l
1.8 5.25 V
PMOS Switch Resistance 0.110 Ω
NMOS Switch Resistance 0.085 Ω
NMOS Switch Leakage Current V
SW1A
= V
SW1B
= 5.5V, V
IN
= 5.5V 0.1 5 µA
PMOS Switch Leakage Current V
SW1A
= V
SW1B
= 0V, V
IN
= 5.5V 0.1 10 µA
Feedback Voltage (Note 4)
l
0.585 0.6 0.612 V
Feedback Input Current V
FB1
= 0.6V 1 50 nA
Average Current Limit (Note 3)
l
1.65 2.1 A
Reverse Current Limit (Note 3) 375 mA
Maximum Duty Cycle V
FB1
= 0.55V
l
85 94 %
Minimum Duty Cycle V
FB1
= 0.66V
l
0 %
PGOOD Threshold V
FB1
Falling –12 –9 –6 %
Power Good Hysteresis V
FB1
Returning Good 3 %
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
, PV
IN1
, PV
IN2
= 3.6V, V
OUT1
= 3.3V, unless
otherwise noted.
tions from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3521I is guaranteed
over the full –40°C to 125°C operating junction temperature range. The
maximum ambient temperature is determined by specific operating
conditions in conjunction with board layout, the rated package thermal
impedance and other environmental factors.
