LTC3523-2_15 Datasheet, PDF (1/16 Pages) Linear Technology – Synchronous 600mA Step-Up and 400mA Step-Down DC/DC Converters

LTC3523/LTC3523-2
Synchronous 600mA Step-Up
and 400mA Step-Down
DC/DC Converters
FEATURES
DESCRIPTION
n _{Dual High Efficiency DC/DC Converters:}
Step-Up (V_OUT = 1.8V to 5.25V, I_SW = 600mA)
Step-Down (V_OUT = 0.615V to 5.5V, I_OUT = 400mA)
n _{1.8V to 5.5V Input Voltage Range}
n _{Up to 94% Efficiency}
n _{Pin Selectable Burst Mode}^® _Operation
n _{45μA Quiescent Current in Burst Mode Operation}
n _{1.2MHz (LTC3523) or 2.4MHz (LTC3523-2)}
Switching Frequency
n _{Independent Power Good Indicator Outputs}
n _{Integrated Soft-Start}
n _{Thermal and Overcurrent Protection}
n _{<3μA Quiescent Current in Shutdown}
n _{Small 16-Lead 3mm × 3mm × 0.75mm QFN Package}
APPLICATIONS
n _{Digital Cameras}
n _{Medical Instruments}
n _{Industrial Handhelds}
n _{GPS Navigators}
The LTC^®3523/LTC3523-2 combine a 600mA step-up
DC/DC converter with a 400mA synchronous step-down
DC/DC converter in a tiny 3mm × 3mm package. The
1.2MHz/2.4MHz switching frequencies minimize the
solution footprint while maintaining high efficiency. Both
converters feature soft-start and internal compensation,
simplifying the design.
Both the step-up and step-down converters are current
mode controlled and utilize an internal synchronous rec-
tifier for high efficiency. The step-up supports 0% duty
cycle operation and the step-down converter supports
100% duty cycle operation to extend battery run time.
If the MODE pin is held high, both converters automati-
cally transition between Burst Mode operation and PWM
operation improving light load efficiency. Fixed, low noise
1.2MHz/2.4MHz PWM operation is selected when MODE
is grounded.
The LTC3523/LTC3523-2 provide a sub-3μA shutdown
mode, overtemperature shutdown and current limit pro-
tection on both converters. The LTC3523/LTC3523-2 are
housed in a 16-lead 3mm × 3mm × 0.75mm QFN package.
L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V_IN
1.8V TO 3.2V
+
2-CELL
ALKALINE
V_OUT1
STEP-UP
OUTPUT
3.3V
200mA
10μF
47μF
4.7μH
V_IN1 V_IN2 V_BAT
SW1
SW2
4.7μH
634k
V_{OUT LTC3523}
FB2
FB1
MODE
V_IN
PGOOD1
PGOOD2
365k
SHDN1
SHDN2
GND1 GND2 GND3
10pF 511k
511k
OFF ON
OFF ON 3523 TA01a
V_OUT2
STEP-DOWN
OUTPUT
10μF
1.2V
200mA
LTC3523 Efficiency and Power
Loss vs Load Current
100
1000
90
80
EFFICIENCY
100
70
60
P0WER LOSS
50
10
40
30
20
10
0
0.1
V_IN = 2.4V
V_OUT1 = 3.3V
V_OUT2 = 1.2V ₁
f_OSC = 1.2MHz
STEP-UP
STEP-DOWN
0.1
1
10
100
1000
LOAD CURRENT (mA)
3523 TA01b
3523fb
1