LM2750 Low Noise Switched Capacitor Boost Regulator
July 2004
LM2750
Low Noise Switched Capacitor Boost Regulator
General Description
The LM2750 is a regulated switched-capacitor doubler that
produces a low-noise output voltage. The 5.0V output volt-
age option (LM2750-5.0) can supply up to 120mA of output
current over a 2.9V to 5.6V input range, as well as up to
40mA of output current when the input voltage is as low as
2.7V. An adjustable output voltage option with similar output
current capabilities is also available (LM2750-ADJ). The
LM2750 has been placed in National’s 10-pin LLP, a pack-
age with excellent thermal properties that keeps the part
from overheating under almost all rated operating conditions
A perfect fit for space-constrained, battery-powered applica-
tions, the LM2750 requires only 3 external components: one
input capacitor, one output capacitor, and one flying capaci-
tor. Small, inexpensive ceramic capacitors are recom-
mended for use. These capacitors, in conjunction with the
1.7MHz fixed switching frequency of the LM2750, yield low
output voltage ripple, beneficial for systems requiring a low-
noise supply. Pre-regulation minimizes input current ripple,
reducing input noise to negligible levels.
A tightly controlled soft-start feature limits inrush currents
during part activation. Shutdown completely disconnects the
load from the input. Output current limiting and thermal
shutdown circuitry protect both the LM2750 and connected
devices in the event of output shorts or excessive current
loads.
Features
n
Inductorless solution: Application requires only 3 small
ceramic capacitors
n
Fixed 5.0V output and adjustable output voltage options
available
n
85% Peak Efficiency
70% Average Efficiency over Li-Ion Input Range
(2.9V-to-4.2V)
n
Output Current up to 120mA with 2.9V
≤
V
IN
≤
5.6V
Output Current up to 40mA with 2.7V
≤
V
IN
≤
2.9V
n
Wide Input Voltage Range: 2.7V to 5.6V
n
Fixed 1.7MHz switching frequency for a low-noise,
low-ripple output signal
n
Pre-regulation minimizes input current ripple, keeping
the battery line (V
IN
) virtually noise-free
n
Tiny LLP package with outstanding power dissipation:
Usually no derating required.
n
Shutdown Supply Current less than 2µA
Applications
n
n
n
n
White and Colored LED-based Display Lighting
Cellular Phone SIM cards
Audio Amplifier Power Supplies
General Purpose Li-Ion-to-5V Conversion
Typical Application Circuit
20035101
© 2004 National Semiconductor Corporation
DS200351
www.national.com
NSC [ NATIONAL SEMICONDUCTOR ]
