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, Inc.
MIC2224
Ordering Information
(1)
Part Number
MIC2224YML
Output
Voltage
Adj.
Junction
Temp. Range
–40°C to +125°C
Package
10-Pin 3mm x 3mm MLF
®
Lead Finish
Pb-Free
Pin Configuration
SW 1
VIN 2
VIN 3
EN 4
AVIN
5
EP
10 PGND
9 VOUT
8 VOUT
7 AGND
6 DAC
10-Pin MLF
®
(ML)
Pin Description
Pin Number
1
2, 3
4
5
6
Pin Name
SW
VIN
EN
AVIN
DAC
Pin Function
Switch (Output): Internal power MOSFET output switches.
Supply Voltage (Input): Requires bypass capacitor to GND.
A low level EN will power down the device, reducing the quiescent current to under
5µA (typ 1µA).
Supply Voltage (Input): Requires bypass capacitor to GND.
DAC Control Input. Provides control of output voltage. The output voltage is 3 X the
DAC voltage. (Ex. 0.5VDAC = 1.5V
OUT
). Bypass mode is enabled when the DAC
voltage exceeds 1.2V.
Signal Ground of chip.
Source of Internal P-Channel MOSFET and Feedback of internal PWM regulator.
Power Ground of chip.
Connect to ground.
7
8, 9
10
EP
AGND
VOUT
PGND
Exposed Pad
September 2006
2
M9999-091106
Micrel, Inc.
MIC2224
Absolute Maximum Ratings
(1)
Supply Voltage (V
IN
) ............................................... 0V to 6V
Output Switch Voltage (V
SW
). ...........................................6V
DAC Input Voltage (V
DAC
)............................ 0V to V
IN
+0.3V
Output Switch Current (I
SW
)...........................................2.5A
Logic Input Voltage (V
EN
) ............................ 0V to V
IN
+0.3V
Storage Temperature (T
s
) .........................–65°C to +150°C
Operating Ratings
(2)
Supply voltage (V
IN
) ....................................... 2.7V to +5.5V
Output Voltage (V
OUT
). ........................................ 0V to 5.5V
DAC Input Voltage (V
DAC
).................................... 0.1V to V
IN
Junction Temperature (T
J
) ........................ –40°C to +125°C
Thermal Resistance
MLF
®
-10 (θ
JA
) ....................................................60°C/W
Electrical Characteristics
(4)
V
IN
= V
EN
= 3.6V; V
DAC
= 0.6V; L = 4.7µH; C
OUT
= 1µF; T
A
= 25°C,
bold
values indicate –40°C< T
J
< +125°C, unless noted.
Parameter
Supply Voltage Range
Total Quiescent Current
Shutdown Current
Maximum Duty Cycle
Regulation
Output Voltage
Output Voltage Line Regulation
Output Voltage Load Regulation
Output
Switch On-Resistance
Current limit (Peak SW Current)
Oscillator
Frequency
Enable / UVLO
Enable Pin Threshold
Enable Pin Hysteresis
Enable Pin Input Current
EN high to 90% VOUT
Under-Voltage Lockout Threshold
UVLO Hysteresis
DAC Input
DAC Input Current
Output Voltage/DAC Voltage
Bypass Switch
Bypass Switch Threshold
Bypass Switch Hysteresis
Bypass Transition Time
Bypass Switch On-Resistance
Bypass Switch Leakage
Bypass Over-Current Limit
Current Limit Retry Time
Current Limit Retry Duty Cycle
1
1.4
32
12.5
1.176
1.2
35
10
40
5
2.5
1.224
V
mV
µs
mΩ
µA
A
µs
%
M9999-091106
(internally set)
0.15
3
2
µA
V/V
(turn-on)
0.5
0.9
30
0.01
25
2.6
85
1
50
2.7
1.3
V
mV
µA
µs
V
mV
1.8
2
2.2
MHz
ISW = -100mA, High-Side Switch
ISW = 100mA , Low-Side Switch
0.65
0.55
0.6
0.85
0.75
0.85
1.6
Ω
Ω
A
VDAC = 0.6V, ILOAD =0mA
3.0V
≤
VIN
≤
4.5, ILOAD= 10mA
0mA < IOUT < 500mA
1.746
1.8
0.05
0.2
1.854
0.5
V
%/V
%
VDAC = 0.6V VOUT = 2.4V (regulator on, not switching)
VEN = 0V (regulator off)
100
Condition
Min
2.7
360
1
Typ
Max
5.5
450
5
Units
V
µA
µA
%
September 2006
3
Micrel, Inc.
Parameter
Over Temperature Shutdown
Shutdown Temperature
Over Temperature Shutdown
Hysteresis
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
4. Specification for packaged product only.
MIC2224
Condition
Min
Typ
160
20
Max
Units
°C
°C
September 2006
4
M9999-091106
Micrel, Inc.
MIC2224
Typical Characteristics
Efficiency 2.7V
OUT
100
95
EFFICIENCY (%)
EFFICIENCY (%)
90
85
80
75
70
0
0.1 0.2 0.3 0.4 0.5
OUTPUT CURRENT (A)
0.6
3.6V
IN
4.2V
IN
3V
IN
100
95
90
85
80
75
70
65
60
0
0.1 0.2 0.3 0.4 0.5
OUTPUT CURRENT (A)
0.6
3V
IN
3.5V
IN
4V
IN
EFFICIENCY (%)
Efficiency 1.8V
OUT
100
95
90
85
80
75
70
65
60
55
50
0
Efficiency 1.5V
OUT
3V
IN
3.6V
IN
4.2V
IN
0.1 0.2 0.3 0.4 0.5
OUTPUT CURRENT (A)
0.6
Efficiency 1.2V
OUT
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
0
0.1 0.2 0.3 0.4 0.5
OUTPUT CURRENT (A)
0.6
3V
IN
EFFICIENCY (%)
3.6V
IN
4.2V
IN
Efficiency 0.9V
OUT
100
3V
IN
90
80
70
60
50
40
30
20
10
0
0
0.1 0.2 0.3 0.4 0.5
OUTPUT CURRENT (A)
0.6
100
3.6V
IN
4.2V
IN
Efficiency 0.6V
OUT
EFFICIENCY (%)
90 3V
IN
80
70
60
50
40
0
0.1 0.2 0.3 0.4 0.5
OUTPUT CURRENT (A)
0.6
3.6V
IN
4.2V
IN
Load Regulation
1.827
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
1.818
1.809
1.800
1.791
V
OUT
= 1.8V
1.782 V
DAC
= 0.6V
V
IN
= 3.6V
1.773
0 100 200 300 400 500 600
LOAD CURRENT (mA)
1.836
1.827
1.818
1.809
1.800
1.791
1.782
1.773
1.764
1.755
Output Voltage
vs. Temperature
3.3
3.2
V
OUT
/DAC
3.1
3.0
2.9
2.8
V
OUT
/DAC
vs. Temperature
V
DAC
= 0.6V
1.746
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
2.7
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
4.5
4.0
3.5
V
OUT
/DAC
3.0
2.5
2.0
1.5
1.0
0.5
0
0
Output Voltage
vs. DAC Voltage
2.20
2.15
FREQUENCY (MHz)
2.10
2.05
2.00
1.95
1.90
1.85
Frequency
vs. Temperature
QUIESCENT CURRENT (µA)
450
400
350
300
250
200
150
100
50
Quiescent Current
vs. Temperature
125°C
-40°C
25°C
0.2 0.4 0.6 0.8 1.0 1.2 1.4
DAC VOLTAGE (V)
1.80
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
V
IN
= 3.6V
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
September 2006
5
M9999-091106
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