LM3370 Datasheet, PDF (1/23 Pages) National Semiconductor (TI) – Dual Synchronous Step-Down DC-DC Converter with Dynamic Voltage Scaling Function

PRELIMINARY
December 2005
LM3370
Dual Synchronous Step-Down DC-DC Converter with
Dynamic Voltage Scaling Function
General Description
LM3370 is a dual step-down DC-DC converter optimized for
powering an ultra-low voltage circuits from a single Li-Ion
battery and input rail ranging from 2.7V to 5.5V. It provides
two outputs with 600mA load per channel. The output volt-
age range varies from 1V to 3.3V and can be dynamically
controlled using the I²C compatible interface. This dynamic
voltage scaling function allows processors to achieve maxi-
mum performance at the lowest power level. The I²C com-
patible interface can also be used to control auto PFM-PWM/
PWM mode selection and other performance enhancing
features.
The LM3370 offers superior features and performance for
portable systems with complex power management require-
ments. Automatic intelligent switching between PWM low-
noise and PFM low-current mode offers improved system
efficiency. Internal synchronous rectification enhances the
converter efficiency without the use of futher external device.
There is a power-on-reset function that monitors the level of
the output voltage to avoid unexpected power losses. The
independent enable pin for each output allows for simple and
effective power sequencing.
LM3370 is available in a 4mm by 5mm 16-lead non-pullback
LLP package. A high switching frequency — 2MHz
(typ) — allows use of tiny surface-mount components includ-
ing a 2.2µH inductor.
Default fixed voltages for the 2 voltage outputs can be
customized to fit system requirements by contacting National
Semiconductor Corporation.
Features
n I²C compatible interface
— V_OUT1 = 1V to 2V in 50mV steps
— V_OUT2 = 2.3V to 3.3V in 100mV steps
— Automatic PFM/PWM mode switching & Forced PWM
mode for low noise operation
— Spread Spectrum capability using I²C
n 600mA load per channel
n 2MHz PWM fixed switching frequency (typ.)
n Internal synchronous rectification for high efficiency
n Internal soft start
n Power-on-reset function for both outputs
n 2.7V ≤ V_IN ≤ 5.5V
n Operates from a single Li-Ion cell or 3 cell NiMH/NiCd
batteries and 3.3V/5.5V fixed rails
n 2.2µH Inductor, 4.7µF Input and 10µF Output Capacitor
per channel
n 16-lead LLP Package (4mm x 5mm x 0.8mm)
Applications
n Baseband Processors
n Application Processors (Video, Audio)
n I/O Power
n FPGA Power and CPLD
© 2005 National Semiconductor Corporation DS201673
www.national.com