December 2004
LM2770
High Efficiency Switched Capacitor Step-Down DC/DC
Regulator with Sleep Mode
General Description
Features
n
High Efficiency Multi-Gain Architecture: Peak Power
The LM2770 is a switched capacitor step-down regulator
that is ideal for powering low-voltage applications in portable
systems. The LM2770 can supply load currents up to 250mA
and operates over an input voltage range of 2.7V to 5.5V.
This makes the LM2770 a great choice for systems powered
by 1-cell Li-Ion batteries and chargers. The output voltage of
the LM2770 can be dynamically switched between two out-
put levels with a logic input pin. Output voltage pairs cur-
rently available include 1.2V/1.5V and 1.2V/1.575V. Other
pairs of voltage options can be developed upon request.
>
Efficiency 85%
n Output Voltage Pairs: 1.2V/1.5V and 1.2V/1.575V
n Dynamic Output Voltage Selection
n
n
n
3% Output Voltage Accuracy
Output Currents up to 250mA
2.7V to 5.5V Input Range
n Low-Supply-Current Sleep Mode
n
n
n
n
n
55µA Quiescent Supply Current in Full-Power Mode
Soft-Start
Short-Circuit Protection in Full-Power Mode
Current-Limit Protection in Sleep Mode
LLP-10 Package (3mm x 3mm x 0.8mm)
LM2770 efficiency is superior to both fixed-gain switched
capacitor buck regulators and low-dropout linear regulators
(LDO’s). Multiple fractional gains maximize power efficiency
over the entire input voltage and output current ranges. The
LM2770 can also be switched into a low-power sleep mode
when load currents are light (≤ 20mA). In sleep mode, the
charge pump is off, and the output is driven with a low-noise,
low-power linear regulator.
Applications
n DSP Power Supplies
n Baseband Power Supplies
n Mobile Phones and Pagers
n Portable Electronic Equipment
Soft-start, short-circuit protection, current-limit protection,
and thermal-shutdown protection are also included. The
LM2770 is available in National’s small 10-pin Leadless
Leadframe Package (LLP-10).
Typical Application Circuit
LM2770 Efficiency vs.
Low-Dropout Linear Regulator (LDO) Efficiency
20126011
20126001
© 2004 National Semiconductor Corporation
DS201260
www.national.com