MIC2224
High Efficiency 2MHz PWM Buck Converter with
DAC Input and 40mΩ Bypass Switch
General Description
The MIC2224 is a high efficiency 2MHz PWM synchronous
buck switching regulator optimized for powering 2.5G and
3G CDMA RF Power Amplifiers. The output voltage of
MIC2224 can be dynamically adjusted with an external
DAC to maximize PA efficiency versus required output
power. When the PA requires the highest power, the DAC
can be used to enable a low on-resistance, 40mΩ, bypass
switch that powers the PA directly from the battery.
The 2MHz PWM operation of MIC2224 allows the smallest
possible components. It also allows the device to easily
meet stringent W-CDMA V
OUT
response specifications.
The MIC2224 operates from a 2.7V to 5.5V input, making
it ideal for single cell Li-Ion applications. The device
features built-in power MOSFETs that can supply up to
600mA of output current in PWM mode, or over 1A in
bypass mode. The MIC2224 can operate with a maximum
duty cycle of 100% for use in low-dropout conditions.
The MIC2224 has a junction temperature range of
–40°C to +125°C and is available in a 10-pin 3mm x 3mm
MLF
®
package.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
2.7V to 5.5V input voltage range
DAC-adjustable output voltage down to 0.3V
600mA output current in PWM mode
Internally protected 40mΩ bypass switch
Allows direct connection of battery to load
Over 95% efficient
Fully integrated MOSFET switches
Constant 2MHz PWM operation
Internal soft-start
1% line and load regulation
<1µA shutdown current
Under-voltage lockout
Thermal shutdown and current limit protection
–40°C to +125°C junction temperature range
Applications
•
Cellular phones
•
PDAs
Typical Application
L1
4.7µH
V
IN
2.6V to 5.5V
2, 3
5
MIC2224
VIN
AVIN
ENABLE
DAC
AGND
PGND
10
7
SW
VOUT
1
8, 9
V
OUT
5.4
4.8
4.2
V
OUT
(V)
3.6
2.4
1.2
0.6
V
IN
= 4.2V
Bypass
Mode
AC
C1
1µF
4
DAC
6
C2
1µF
GND
GND
2MHz PWM Converter with DAC Input
and 40mΩ Bypass Switch
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
V
DAC
(V)
MLF and
MicroLeadFrame
are registered trademarks or Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
September 2006
1
V
O
UT
1.8
=
V
D
X
3.0
3
M9999-091106
MICREL [ MICREL SEMICONDUCTOR ]
