
August, 2004
1
M0385-080204
MIC5255
Micrel
MIC5255
150mA Low Noise
μ
Cap CMOS LDO
General Description
The MIC5255 is an efficient, precise CMOS voltage regulator
optimized for ultra-low-noise applications. It offers 1% initial
accuracy, extremely-low dropout voltage (135mV at 150mA)
and low ground current (typically 90
μ
A). The MIC5255 pro-
vides a very-low-noise output, ideal for RF applications
where a clean voltage source is required. A noise bypass pin
is also available for further reduction of output noise.
Designed specifically for handheld and battery-powered de-
vices, the MIC5255 provides a TTL-logic-compatible enable
pin. When disabled, power consumption drops nearly to zero.
The MIC5255 also works with low-ESR ceramic capacitors,
reducing the amount of board space necessary for power
applications, critical in handheld wireless devices.
Key features include current limit, thermal shutdown, faster
transient response, and an active clamp to speed up device
turn-off. Available in the 6-pin 2mm
×
2mm MLF package,
the IttyBitty SOT-23-5 package and the new Thin SOT-23-
5, which offers the same footprint as the standard IttyBitty
SOT-23-5, but only 1mm tall. The MIC5255 offers a range of
output voltages.
All support documentation can be found on Micrel’s web
site at www.micrel.com.
Features
Input voltage range: 2.7V to 6.0V
Thin SOT package: 1mm height SOT-23-5
Ultra-low output noise: 30
μ
V(rms)
Stability with ceramic output capacitors
Ultra-low dropout: 135mV @ 150mA
High output accuracy:
1.0% initial accuracy
2.0% over temperature
Low quiescent current: 90
μ
A
Tight load and line regulation
TTL-Logic-controlled enable input
“Zero” off-mode current
Thermal shutdown and current limit protection
Applications
Cellular phones and pagers
Cellular accessories
Battery-powered equipment
Laptop, notebook, and palmtop computers
Consumer/personal electronics
Micrel, Inc. 1849 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 474-1000 http://www.micrel.com
IttyBitty is a registered trademark of Micrel, Inc.
MicroeadFrame and MLF are trademarks of Amkor Technology.
Typical Application
C
OUT
= 1.0
μ
F
Ceramic
C
IN
= 1.0
μ
F
Ceramic
1
5
2
3
4
C
BYP
= 0.01
μ
F
Enable
Shutdown
EN
V
OUT
MIC5255-x.xBM5
EN (pin 3) may be
connected directly
to IN (pin 1).
V
IN
MIC5255-x.xBML
1
EN
6
C
BYP
(optional)
V
IN
V
OUT
C
OUT
5
4
2
3
ENABLE
SHUTDOWN
Ultra-Low-Noise Regulator Application