Micrel MIC2205 User Manual

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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 MLF10L 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

2.7V to 5.5V

V

GND

IN

C1

1µF

LowQ

C2

0.1µF

MIC2205

8

VIN

4

AVINSWLDO

6

EN

7

LOWQ

3

BIAS

PGND

AGND

10 1

FB

Adjustable Output Buck Regulator with LOWQ™ Mode

2.2µH

9

2

R1 100k

5

R2 125k

C3 100pF

V

C4

2.2µF

GND

OUT

1.8V

Efficiency

100

95 90 85 80 75 70 65

EFFICIENCY (%)

60 55 50

0 100 200 300 400 500 600

OUT

VIN=3V

VIN=3.6V

VIN=4.2V

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

A

Ordering Information

Part Number Output Voltage

MIC2205-1.3YML 1.3V –40° to +125°C 3x3 MLF-10L Pb-free MIC2205-1.38YML 1.38V –40° to +125°C 3x3 MLF-10L Pb-free MIC2205-1.5YML 1.5V –40° to +125°C 3x3 MLF-10L Pb-free MIC2205-1.58YML 1.58V –40° to +125°C 3x3 MLF-10L Pb-free MIC2205-1.8YML 1.8V –40° to +125°C 3x3 MLF-10L Pb-free MIC2205-1.85YML 1.85V –40° to +125°C 3x3 MLF-10L Pb-free MIC2205YML Adj. –40° to +125°C 3x3 MLF-10L Pb-free

Note:

1. Other Voltage options available. Contact Micrel for details.

(1)

Junction Temp. Range Package Lead Finish

Pin Configuration

PGND

GND

LDO BIAS

1 2 3

10

SW

9

VIN

8

Pin Description

Pin Number Pin Name Pin Function

1 AGND Analog (signal) Ground. 2 LDO LDO Output (Output): Connect to V 3 BIAS

4 AVIN

5 FB

6 EN

7

8 VIN Supply Voltage (Input): Supply voltage for the internal switches and drivers. 9 SW Switch (Output): Internal power MOSFET output switches.

10 PGND Power Ground.

EP GND Ground, backside pad.

_____

LOWQ

AVIN

4

FB EN

5

EP

7 6

3mm x 3mm MLF-10L (ML)

for LDO mode operation.

OUT

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 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.

and an internal resistor network sets the output

OUT

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Micrel, Inc. MIC2205

Absolute Maximum Ratings

(1)

Supply Voltage (VIN) ............................................ +6V

Output Switch Voltage (V Output Switch Current (I Logic Input Voltage (V Storage Temperature (T ESD Rating

(3)

....................................................... 3kV

Electrical Characteristics

) ............................... +6V

SW

)................................... 2A

SW

EN,VLOWQ

).............. -0.3V to VIN

)................ -60°C to +150°C

s

(4)

Operating Ratings

Supply Voltage (VIN)............................+2.7V to +5.5V

Logic Input Voltage (V Junction Temperature (T Junction Thermal Resistance 3x3 MLF-10L (θ

(2)

EN,VLOWQ

)...................................60°C/W

JA

) ..............-0.3V to VIN

)..............–40°C to +125°C

J

VIN = VEN = V

=3.6V; L = 2.2µH; C

LOWQ

= 2.2µF; TA = 25°C, unless noted. Bold values indicate –40°C< TJ < +125°C

OUT

Parameter Condition Min Typ Max Units

Supply Voltage Range Under-Voltage Lockout

(turn-on) 2.45 2.55 2.65 V

2.7

5.5

V

Threshold UVLO Hysteresis 100 mV Quiescent Current, PWM

= 0.9 * V

V

FB

(not switching) 690

NOM

900

µA

mode Quiescent Current, LDO

V

LOWQ

= 0V;I

= 0mA 16

OUT

29

µA

mode Shutdown Current VEN = 0V 0.01 [Adjustable] Feedback

Voltage

± 1% ± 2% (over temperature)

[Fixed Output] Voltages Nominal V

tolerance

OUT

0.99

0.98

-1

-2

1

5

1.01

1.02

+1

+2

µA

V

%

FB pin input current 1 nA Current Limit in PWM Mode VFB = 0.9 * V Output Voltage Line

Regulation Output Voltage Load

V

> 2V; VIN = V

OUT

< 2V; VIN = 2.7V to 5.5V; I

V

OUT

20mA < I

LOAD

NOM

+300mV to 5.5V; I

OUT

LOAD

= 100mA

0.75

0.13 %

< 300mA 0.2

1

1.85

0.5

A

%

Regulation, PWM Mode Output Voltage Load

Regulation, LDO Mode Maximum Duty Cycle

PWM Switch ONResistance

100µA < I V

LOWQ

V

≤ 0.4V

FB

LOAD

= 0V

< 50mA

ISW = 50mA VFB = 0.7V

= -50mA VFB = 1.1V

I

SW

(High Side Switch)

FB_NOM

Oscillator Frequency

(Low Side Switch)

0.1

100

%

0.4

1.8

2

0.2

2.2

%

Ω

MHz

LOWQ threshold voltage

0.5

0.85

LOWQ Input Current 0.1 Enable Threshold

0.5

0.85

Enable Input Current 0.1

I

LDO Dropout Voltage

April 2005

= 50mA Note 5

OUT

110

3

1.3 2

V

µA

V

µA

mV

M9999-041105

www.micrel.com

Micrel, Inc. MIC2205

Parameter Condition Min Typ Max Units

60

75

120

Output Voltage Noise LDO Current Limit LOWQ = 0V; V

Over-Temperature Shutdown

Over-Temperature 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: 1.5kΩ in series with 100pF.

4. Specification for packaged product only.

5. 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.

LOWQ = 0V; C

160

20

= 2.2μF, 10Hz to 100kHz

OUT

= 0V (LDO Mode)

OUT

µVrms

mA

°C

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Typical Characteristics – PWM Mode

80 70 60 50 40 30 20

GAIN (dB)

10

0

-10

-20

1E+2 1E+3 1E+4 1E+5 1E+6

100

95 90 85 80 75 70 65

EFFICIENCY (%)

60 55 50

Bode Plot

Phase

VIN=3.6V

=1.8V

V

OUT

L=2.2 H C

=2.2 F

OUT

= 120pF

C

FF

1k FREQUENCY (Hz)

1.5V

VIN=4.2V

0 100 200 300 400

OUTPUT CURRENT (mA)

10k

Efficiency

OUT

VIN=3.6V

Gain

100k

VIN=3V

1M

144 126 108 90 72 54 36 18 0

-18

-36

PHASE (°)

2.5V

Efficiency

100

95 90 85 80 75 70 65

EFFICIENCY (%)

60 55 50

0 100 200 300 400

95 90 85 80 75 70 65

EFFICIENCY (%)

60 55 50

0 100 200 300 400

OUT

VIN=3V

VIN=3.6V

VIN=4.2V

OUTPUT CURRENT (mA)

1.38V

VIN=4.2V

OUTPUT CURRENT (mA)

Efficiency

OUT

VIN=3.6V

VIN=3V

1.8V

Efficiency

100

95 90 85 80 75 70 65

EFFICIENCY (%)

60 55 50

0 100 200 300 400 500 600

95 90 85 80 75 70 65

EFFICIENCY (%)

60 55 50

0 100 200 300 400

OUT

VIN=3V

VIN=3.6V

VIN=4.2V

OUTPUT CURRENT (mA)

1.2V

Efficiency

OUT

VIN=3V

VIN=3.6V

VIN=4.2V

OUTPUT CURRENT (mA)

1.0V

Efficiency

90 85 80 75 70 65

EFFICIENCY (%)

60 55 50

0 100 200 300 400 500 600

2.2

2.15

2.1

2.05 2

1.95

1.9

FREQUENCY (MHz)

1.85

1.8

-40 -20 0 20 40 60 80 100 120

OUT

VIN=3V

VIN=3.6V

VIN=4.2V

OUTPUT CURRENT (mA)

Frequency

vs. Temperature

VIN=3.6V

TEMPERATURE (°C)

1.010

1.008

1.006

1.004

1.002

1.000

0.998

0.996

0.994

FEEDBACK VOLTAGE (V)

0.992

0.990

1200

1000

CURRENT LIMIT (mA)

Load Regulation

VIN=3.6V LowQ = V

IN

0 100 200 300 400

OUTPUT CURRENT (mA)

Peak Current Limit vs. Supply Voltage

800

600

400

200

LowQ = V

0

2.7 3.4 4.1 4.8 5.5

IN

SUPPLY VOLTAGE (V)

Quiescent Current vs. Supply Voltage

900 800 700 600 500 400 300 200

VIN=3.6V

100

V

QUIESCENT CURRENT (µA)

ENABLE THRESHOLD (V)

=0.9V

FB

0

2.7 3.4 4.1 4.8 5.5 SUPPLY VOLTAGE (V)

Enable Threshold

vs. Supply Voltage

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

LowQ = V

0.5

2.7 3.4 4.1 4.8 5.5

IN

SUPPLY VOLTAGE (V)

April 2005

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Micrel MIC2205 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual