SI9174 Datasheet, PDF (1/17 Pages) Vishay Siliconix – High Performance Step-Down DC-DC Converter With Dynamically Adjustable Output Voltage

Si9174
Vishay Siliconix
High Performance Step-Down DC-DC Converter
With Dynamically Adjustable Output Voltage
FEATURES
D 2-MHz PWM Operation
D Integrated MOSFET Switches
D 2.6-V to 6.0-V Input Voltage Range
D Minimal Number of External Components
D Up to 96% conversion efficiency
D 600-mA Load Capability
D 100% Duty Cycle Allows Low Dropout
D Integrated Compensation Circuit
D Over-Current Protection
D Shutdown Current < 2 mA
D Thermal Shutdown
D Integrated UVLO
D 10-Pin MSOP and Space Saving MLP33 Packaging
D DAC Input for Dynamic Output Voltage Adjustment
D Synchronizable to13-MHz Clock
D User Selectable PWM, PSM, or AUTO Mode
D PSM Frequency w20 kHz for Inaudible
Harmonics
APPLICATIONS
D W-CDMA Cell Phone
D PDAs/Palmtop PCs
D LCD Modules
D Portable Image Scanners
D GPS Receivers
D Smart Phones
D MP3 Players
D 3G Cell Phone
D Digital Cameras
DESCRIPTION
The Si9174 is a high efficiency 600-mA step down converter
with internal low on resistance power MOSFET switch and
synchronous rectifier transistors. It is designed to convert one
cell LiIon battery or three cell alkaline battery voltages to a
dynamically adjustable dc output. The voltage on the DAC pin
controls the output voltage. The output voltage is adjustable
between 0.4 V and the input voltage V_IN less a small dropout
voltage and settles in <30 ms.
In order to insure efficient conversion throughout the entire
load range, PWM (pulse width modulation), PSM (pulse
skipping mode) or Auto mode can be selected. In PWM mode,
2-MHz switching permits use of small external inductor and
capacitor sizes allowing one of the smallest solutions. To
TYPICAL APPLICATIONS CIRCUIT
minimize system noise, the switching frequency can be
synchronized to an external 13-MHz clock.
PSM mode provides increased efficiency at light loads. In PSM
mode the oscillator frequency is kept above 20 kHz to avoid
audio band interference. When operating in Auto mode, the
converter automatically selects operating in either PWM or
PSM mode according to load current demand.
The Si9174 is available in the10-pin MSOP and the even
smaller MLP33 package and is specified to operate over the
industrial temperature range of –40_C to 85_C. The Si9174
packaged in the MLP33 package is available in both standard
and lead (Pb)-free.
BATTERY
C_IN
10 mF
13 MHz
DAC
ENABLE
PWM/PSM/AUTO
V_IN
LX
V_DD
Si9174
SYNC
DAC
SD
MODE
PGND
FB
AGND
2.2 mH
C_OUT
4.7 mF
Document Number: 71668
S-41148—Rev. C, 14-jun-04
V_OUT
R₁
R₂
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