MIC2205
2MHz PWM Synchronous Buck
Regulator with LDO Standby Mode
General Description
The Micrel MIC2205 is a high efficiency 2MHz PWM
synchronous buck (step-down) regulator that
features a
LOWQ™
LDO standby mode that draws
only 18µA of quiescent current. The MIC2205
allows an ultra-low noise, small size, and high
efficiency solution for portable power applications.
In PWM mode, the MIC2205 operates with a
constant frequency 2MHz PWM control. Under light
load conditions, such as in system sleep or standby
modes, the PWM switching operation can be
disabled to reduce switching losses. In this light
load
LOWQ™
mode, the LDO maintains the output
voltage and draws only 18µA of quiescent current.
The LDO mode of operation saves battery life while
not introducing spurious noise and high ripple as
experienced with pulse skipping or bursting mode
regulators.
The MIC2205 operates from 2.7V to 5.5V input and
features internal power MOSFETs that can supply
up to 600mA output current in PWM mode. It can
operate with a maximum duty cycle of 100% for use
in low-dropout conditions.
The MIC2205 is available in the 3mm x 3mm MLF-
10L package with a junction operating 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
•
2.7 to 5.5V supply voltage
•
Light load
LOWQ™
LDO mode
18µA quiescent current
Low noise, 75µVrms
•
2MHz PWM mode
Output current to 600mA
>95% efficiency
100% maximum duty cycle
•
Adjustable output voltage option down to 1V
Fixed output voltage options available
•
Ultra-fast transient response
•
Stable with 1µF ceramic output capacitor
•
Fully integrated MOSFET switches
•
Micropower shutdown
•
Thermal shutdown and current limit protection
•
Pb-free 3mm x 3mm MLF-10L package
•
–40°C to +125°C junction temperature range
Applications
•
Cellular phones
•
PDAs
•
USB peripherals
____________________________________________________________________________________________________
Typical Application
MIC2205
V
IN
2.7V to 5.5V
C1
1µF
8
4
6
VIN
AVIN
EN
LOWQ
BIAS
SW
LDO
9
2
2.2µH
V
OUT
R1
100k
R2
125k
C3
100pF
C4
2.2µF
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
0
1.8V
OUT
Efficiency
V
IN
= 3V
V
IN
= 3.6V
V
IN
= 4.2V
LowQ
C2
0.1µF
7
3
FB
5
PGND AGND
GND
10
1
GND
Adjustable Output Buck Regulator with
LOWQ™
Mode
100 200 300 400 500 600
OUTPUT CURRENT (mA)
Patent Pending
LOWQ
is a trademark of Micrel, 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 2005
M9999-041105
www.micrel.com
Micrel, Inc.
MIC2205
Ordering Information
Part Number
MIC2205-1.3YML
MIC2205-1.38YML
MIC2205-1.5YML
MIC2205-1.58YML
MIC2205-1.8YML
MIC2205-1.85YML
MIC2205YML
Note:
1. Other Voltage options available. Contact Micrel for details.
Output Voltage
(1)
1.3V
1.38V
1.5V
1.58V
1.8V
1.85V
Adj.
Junction Temp. Range
–40° to +125°C
–40° to +125°C
–40° to +125°C
–40° to +125°C
–40° to +125°C
–40° to +125°C
–40° to +125°C
Package
3x3 MLF-10L
3x3 MLF-10L
3x3 MLF-10L
3x3 MLF-10L
3x3 MLF-10L
3x3 MLF-10L
3x3 MLF-10L
Lead Finish
Pb-free
Pb-free
Pb-free
Pb-free
Pb-free
Pb-free
Pb-free
Pin Configuration
AGND 1
LDO 2
BIAS 3
AVIN 4
FB 5
EP
10 PGND
9 SW
8 VIN
7 LOWQ
6 EN
3mm x 3mm MLF-10L (ML)
Pin Description
Pin Number
1
2
3
4
5
Pin Name
AGND
LDO
BIAS
AVIN
FB
Pin Function
Analog (signal) Ground.
LDO Output (Output): Connect to V
OUT
for LDO mode operation.
Internal circuit bias supply. Must be de-coupled to signal ground with a 0.1µF
capacitor and should not be loaded.
Analog Supply Voltage (Input): Supply voltage for the analog control circuitry and
LDO input power. Requires bypass capacitor to GND.
Feedback. Input to the error amplifier. For the Adjustable option, connect to the
external resistor divider network to set the output voltage. For fixed output
voltage options, connect to V
OUT
and an internal resistor network sets the output
voltage.
Enable (Input). Logic low will shut down the device, reducing the quiescent
current to less than 5µA.
Enable LDO Mode (Input): Logic low enables the internal LDO and disables the
PWM operation. Logic high enables the PWM mode and disables the LDO
mode.
Supply Voltage (Input): Supply voltage for the internal switches and drivers.
Switch (Output): Internal power MOSFET output switches.
Power Ground.
Ground, backside pad.
6
EN
_____
LOWQ
VIN
SW
PGND
GND
7
8
9
10
EP
April 2005
2
M9999-041105
www.micrel.com
Micrel, Inc.
MIC2205
Absolute Maximum Ratings
(1)
Supply Voltage (V
IN
) ............................................ +6V
Output Switch Voltage (V
SW
) ............................... +6V
Output Switch Current (I
SW
) ................................... 2A
Logic Input Voltage (V
EN
,V
LOWQ
) .............. -0.3V to V
IN
Storage Temperature (T
s
)................ -60°C to +150°C
ESD Rating
(3)
.......................................................
3kV
Operating Ratings
(2)
Supply Voltage (V
IN
)............................+2.7V to +5.5V
Logic Input Voltage (V
EN
,V
LOWQ
) .............. -0.3V to V
IN
Junction Temperature (T
J
) .............. –40°C to +125°C
Junction Thermal Resistance
3x3 MLF-10L (θ
JA
) ................................... 60°C/W
Electrical Characteristics
(4)
V
IN
= V
EN
= V
LOWQ
=3.6V; L = 2.2µH; C
OUT
= 2.2µF; T
A
= 25°C, unless noted.
Bold
values indicate –40°C< T
J
< +125°C
Parameter
Supply Voltage Range
Under-Voltage Lockout
Threshold
UVLO Hysteresis
Quiescent Current, PWM
mode
Quiescent Current, LDO
mode
Shutdown Current
[Adjustable] Feedback
Voltage
[Fixed Output] Voltages
FB pin input current
Current Limit in PWM Mode
Output Voltage Line
Regulation
Output Voltage Load
Regulation, PWM Mode
Output Voltage Load
Regulation, LDO Mode
Maximum Duty Cycle
PWM Switch ON-
Resistance
Oscillator Frequency
LOWQ threshold voltage
LOWQ Input Current
Enable Threshold
Enable Input Current
LDO Dropout Voltage
I
OUT
= 50mA
Note 5
0.5
V
FB
= 0.9 * V
NOM
V
OUT
> 2V; V
IN
= V
OUT
+300mV to 5.5V; I
LOAD
= 100mA
V
OUT
< 2V; V
IN
= 2.7V to 5.5V; I
LOAD
= 100mA
20mA < I
LOAD
< 300mA
100µA < I
LOAD
< 50mA
V
LOWQ
= 0V
V
FB
≤
0.4V
I
SW
= 50mA V
FB
= 0.7V
FB_NOM
(High Side Switch)
I
SW
= -50mA V
FB
= 1.1V
FB_NOM
(Low Side Switch)
1.8
0.5
100
0.4
0.4
2
0.85
0.1
0.85
0.1
110
2.2
1.3
2
1.3
2
0.75
V
FB
= 0.9 * V
NOM
(not switching)
V
LOWQ
= 0V;I
OUT
= 0mA
V
EN
= 0V
±
1%
±
2% (over temperature)
Nominal V
OUT
tolerance
0.99
0.98
-1
-2
1
1
0.13
0.2
0.1
0.5
0.2
1.85
(turn-on)
Condition
Min
2.7
2.45
2.55
100
690
16
0.01
1
900
29
5
1.01
1.02
+1
+2
Typ
Max
5.5
2.65
Units
V
V
mV
µA
µA
µA
V
%
nA
A
%
%
%
%
Ω
MHz
V
µA
V
µA
mV
April 2005
3
M9999-041105
www.micrel.com
Micrel, Inc.
MIC2205
Parameter
Output Voltage Noise
LDO Current Limit
Over-Temperature
Shutdown
Over-Temperature
Hysteresis
Notes
1.
2.
3.
4.
5.
Condition
LOWQ = 0V; C
OUT
= 2.2μF, 10Hz to 100kHz
LOWQ = 0V; V
OUT
= 0V (LDO Mode)
Min
Typ
75
Max
Units
µVrms
mA
°C
°C
60
120
160
20
Exceeding the absolute maximum rating may damage the device.
The device is not guaranteed to function outside its operating rating.
Devices are ESD sensitive. Handling precautions recommended. Human body model: 1.5kΩ in series with 100pF.
Specification for packaged product only.
Dropout voltage is defined as the input-to-output differential at which the output voltage drops 2% below its nominal value that is
initially measured at a 1V differential. For outputs below 2.7V, the dropout voltage is the input-to-output voltage differential with a
minimum input voltage of 2.7V.
April 2005
4
M9999-041105
www.micrel.com
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