September 2002
LM2618
400mA Sub-miniature, High Efficiency, Synchronous
PWM & PFM Programmable DC-DC Converter
General Description
Key Specifications
n Operates from a single LiION cell (2.8V to 5.5V)
n Internal synchronous rectification provides high
efficiency in both PWM and PFM
The LM2618 step-down DC-DC converter is optimized for
powering low voltage circuits from a single Lithium-Ion cell. It
provides up to 400mA (300mA for B grade), over an input
voltage range of 2.8V to 5.5V. Pin programmable output
voltages of 1.80V, 1.83V, 1.87V or 1.92V allow adjustment
for MPU voltage options without board redesign or external
feedback resistors. Internal synchronous rectification pro-
vides high efficiency in both PWM and PFM operation.
n Pin programmable output voltage (1.80V, 1.83V, 1.87V
and 1.92V)
n 400mA maximum load capability (300mA for B grade)
n
2% PWM mode DC output voltage precision
n 5mV typ PWM mode output voltage ripple
n 180 µA typ PFM mode quiescent current
n 0.02µA typ shutdown mode current
The device has three pin-selectable modes for maximizing
battery life in mobile phones and similar portable applica-
tions. Low-noise PWM mode offers 600kHz fixed-frequency
operation to reduce interference in RF and data acquisition
applications during full-power operation. A SYNC input al-
lows synchronizing the switching frequency in a range of
500kHz to 1MHz to avoid noise from intermodulation with
system frequencies. Low-current hysteretic PFM mode re-
duces quiescent current to 180 µA (typ.) during system
standby. Shutdown mode turns the device off and reduces
battery consumption to 0.02µA (typ.). Additional features
include soft start and current overload protection.
n Internal synchronous rectification for high efficiency
(91% at 3.0VIN, 1.92VOUT
)
n 600kHz PWM mode switching frequency
n SYNC input for PWM mode frequency synchronization
from 500kHz to 1MHz
Features
n Sub-miniature 10-pin micro SMD package
n Only three tiny surface-mount external components
required
The LM2618 is available in a 10 pin micro SMD packge. This
package uses National’s wafer level chip-scale micro SMD
technology and offers the smallest possible size. Only three
small external surface-mount components, an inductor and
two ceramic capacitors are required.
n Uses small ceramic capacitors.
n Internal soft start
n Current overload protection
n Thermal Shutdown Protection
n No external compensation required
Applications
n Mobile Phones
n Hand-Held Radios
n Battery Powered Devices
Typical Application Circuit
20036402
© 2002 National Semiconductor Corporation
DS200364
www.national.com