MIC2238
2.5MHz Dual Phase
PWM Buck Regulator
General Description
The Micrel MIC2238 is dual output 2-phase synchronous
buck (step down) PWM DC/DC switching regulator. Power
conversion efficiencies of above 95% are easily obtainable
for a wide range of applications and loads. An ultra-low
quiescent current of 28µA at light loads assures minimum
current draw in battery powered applications that require
standby modes. The 2.5MHz PWM operation of MIC2238
allows the use of miniature 1µH, 2.2µH or 4.7µH inductor
with the use of 2.2µF ceramic output capacitor.
The MIC2238 operates from 2.5V to 5.5V input and is
available in fixed output voltage versions to save space
and reduce external component count. The MIC2238-AA’s
(adjustable version) output voltage versions can be
programmed as low as 0.8V
For applications that require the lowest noise performance,
the /FPWM pin allows the automatic Trickle mode to be
disabled, remaining in full PWM mode. To maximize
battery life in low-dropout conditions, MIC2238 can
operate with a maximum duty cycle of 100%.
The MIC2238 is available in a space-saving 3mm x 3mm
MLF
®
-12L package with a junction temperature range from
-40°C to +125°C.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Input voltage range: 2.5V to 5.5V
Dual output voltages running out of phase
28µA quiescent current
Fixed output voltage versions
Adjustable version down to 0.8V
Low noise 2.5MHz PWM operation
800mA output current capability for each channel
Stable with 2.2µH inductor, 2.2µF ceramic cap
Automatic switching into light load mode of operation
/FPWM pin allows low noise all-PWM mode operation
Power good output with internal 5µA current source
allows sequencing with programmable delay time
Internal soft-start
1µA shutdown current
Built-in soft-start circuitry
Current limit protection
Pb-Free 3mm x 3mm MLF
®
-12L package
Applications
•
Cellular phones
•
PDAs
•
Digital Cameras
•
MP3 Players
___________________________________________________________________________________________________________
Typical Application
MLF and
MicroLead
Frame are registered trademarks of 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
April 2008
M9999-042108
Micrel, Inc.
MIC2238
Ordering Information
Part Number
MIC2238-AAYML
MIC2238-521YML
MIC2238-G4YML
MIC2238-GF9YML
MIC2238-GFHYML
MIC2238-GSYML
MIC2238-GWYML
MIC2238-J4YML
MIC2238-S4YML
MIC2238-SSYML
Note:
Other voltages available. Contact Micrel Marketing for details.
MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
®
V
OUT1
Adj.
1.28V
1.8V
1.8V
1.8V
1.8V
1.8V
2.5V
3.3V
3.3V
V
OUT2
Adj.
1.65V
1.2V
1.545V
1.575V
3.3V
1.6V
1.2V
1.2V
3.3V
Junction
Temperature Range
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
Package
12-Pin 3mm x 3mm MLF
®
12-Pin 3mm x 3mm MLF
®
12-Pin 3mm x 3mm MLF
®
12-Pin 3mm x 3mm MLF
®
12-Pin 3mm x 3mm MLF
12-Pin 3mm x 3mm MLF
®
®
Lead Finish
Pb-Free
Pb-Free
Pb-Free
Pb-Free
Pb-Free
Pb-Free
Pb-Free
Pb-Free
Pb-Free
Pb-Free
12-Pin 3mm x 3mm MLF
®
12-Pin 3mm x 3mm MLF
®
12-Pin 3mm x 3mm MLF
®
12-Pin 3mm x 3mm MLF
®
Pin Configuration
Adjustable
MIC2238-AAYML
®
12-Pin MLF (ML)
(Top View)
Fixed
MIC2238-xxYML
12-Pin MLF
®
(ML)
(Top View)
April 2008
2
M9999-042108
Micrel, Inc.
MIC2238
Pin Description
Pin Number
Adjustable
1
Pin Number
Fixed
–
FB2
Feedback 2: For adjustable voltage options connect the
external resistor divider network to FB2 to set the output
voltage of regulator 2. Nominal value is 0.8V.
Enable 2 input. Logic low powers down regulator 2. Logic
high powers up regulator 2. MIC2238 features built-in soft-
start circuitry that reduces in-rush current and prevents the
output voltage from overshooting at start up.
Analog Supply Voltage: Supply voltage for the analog control
circuitry. Requires bypass capacitor to GND.
Switch node for regulator 2, connected to external inductor.
Analog (signal) ground.
Power ground.
Forced PWM Mode Bar. Grounding this pin forces the device
to stay in constant frequency PWM mode only. Pulling this
pin high enables automatic Trickle mode operation.
Switch node for regulator 1, connected to external inductor.
Supply Voltage: Supply voltage for the internal switches and
drivers.
Power Good Output. This output is pulled down unless the
regulator 1 output voltage is within +6.25% and -8.5% of
regulation. After the output voltage is in regulation, the output
starts to go high with an internal 5µA current source. A delay
time could be programmed by tying a capacitor to this pin.
Enable 1 input. Logic low powers down regulator 1. Logic
high powers up regulator 1. MIC2238 features built-in soft-
start circuitry that reduces in-rush current and prevents the
output voltage from overshooting at start up.
Feedback 1: For adjustable voltage options connect to the
external resistor divider network to FB1 to set the output
voltage of regulator 1. Nominal value is 0.8V.
Output Voltage 2. For fixed output voltage options connect
OUT2 to the output voltage of regulator 2.
Output Voltage 1. For fixed output voltage options connect
OUT1 to the output voltage of regulator 1.
Ground, backside pad.
Pin Name
Pin Name
2
2
EN2
3
4
5
6
7
8
9
3
4
5
6
7
8
9
AVIN
SW2
AGND
PGND
/FPWM
SW1
VIN
10
10
PGOOD
11
11
EN1
12
–
–
EP
–
1
12
EP
FB1
OUT2
OUT1
GND
April 2008
3
M9999-042108
Micrel, Inc.
MIC2238
Absolute Maximum Ratings
(1)
Supply Voltage (V
IN
) .......................................................+6V
Enable 1 Voltage ………………………………………... +6V
Enable 2 Voltage ……………………………………….. +6V
Logic Input Voltage (V
EN
, V
FPWM
)............................ V
IN
to 0V
Storage Temperature (T
S
) .........................-65°C to +150°C
ESD .............................................................................. 2KV
Operating Ratings
(2)
Supply Voltage (V
IN
) ........................................ 2.5V to 5.5V
Junction Temperature (T
J
) .........................-40°C to +125°C
Package Thermal Resistance (θ
JA
) ..........................60°C/W
Electrical Characteristics
(4)
T
A
= 25°C with V
IN
= V
EN1
= V
EN2
=3.6V, V
OUT1
, V
OUT2
, L= 2.2µH, C = 2.2µF, unless otherwise specified.
Bold
values indicate -40ºC
≤
T
J
≤+125ºC..
Parameter
Condition
Min
Typ
Max
Units
Supply Voltage and Current
Supply Voltage Range
UVLO (rising)
UVLO Hysteresis
PWM Mode Supply
Current
Trickle Mode Supply
Current
Shutdown Quiescent
Current
Output Voltage Accuracy
Feedback voltage, V
FB
Output voltage, V
OUT
Feedback bias current
Output Voltage Line
Regulation
Output Voltage Load
Regulation
2.5V
≤
V
IN
≤
5.5V
V
IN
= 5V, I
OUT
= 10mA to 800mA, /FPWM = 0V
V
IN
= 3V; I
OUT
= 10mA to 800mA, /FPWM = 0V
Ripple in Trickle Mode
Logic Inputs
EN Input Threshold
EN Input Current
/FPWM Input Threshold
On
Off
/FPWM Input Current
0.3xV
IN
0.01
1
On
Off
0.3
0.8
0.7
0.01
1
0.6xV
IN
1.2
V
V
µA
V
V
µA
Vin=3.6V; Iout = 1mA; C
OUT
= 2.2µF, L = 2.2µH.
Adjustable
Fixed Output Options
0.780
-2.5
10
0.1
0.5
0.8
0.820
+2.5
V
%
nA
%
/FPWM = Low, I
OUT
= 200mA
/FPWM = High, I
OUT
= 100µA
V
EN
= 0V
2.5
2.3
2.4
100
560
28
0.1
950
50
1
5.5
2.5
V
V
mV
µA
µA
µA
0.5
40
%
mV
April 2008
4
M9999-042108
Micrel, Inc.
MIC2238
Electrical Characteristics (cont.)
(4)
Parameter
Protection
Current Limit
Over Temperature
Shutdown Hysteresis
Control
Maximum Duty Cycle
Oscillator
PWM Mode Frequency
Power Good
Power Good Reset
Threshold
PGOOD Series
Resistance
PGOOD Pull-Up Current
Power Switch
Switch On-Resistance
I
SW
= 150mA (PFET)
I
SW
= 150mA (NFET)
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, 1.5kΩ in series with 100pF.
4. Specification for packaged product only.
Condition
Min
Typ
Max
Units
Peak Switch Current, V
OUT
= 0V
0.9
1.2
20
1.8
A
°C
V
FB
= 0.7V
100
%
2.125
2.5
2.875
MHz
Upper Threshold
Lower Threshold
-14
6.25
-8.5
1
12
%
kΩ
µA
1.4
Output within 8.5% of regulation
5
0.4
0.35
Ω
April 2008
5
M9999-042108
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