MIC2203YMLTR - Micrel, Inc. - Datasheet.Directory

MIC2203

High Efficiency 1MHz Synchronous

Buck Regulator

General Description

The Micrel MIC2203 is a high efficiency 1MHz PWM

synchronous buck switching regulator. The MIC2203

features low noise constant frequency PWM

operation with a low dynamic supply current of

<1mA. The low noise and efficient operation both

make the MIC2203 well suited for sensitive RF, and

audio power applications.

The MIC2203 operates from 2.3V to 5.5V input and

can supply over 300mA of output current with output

voltages down to 0.5V. Additionally, the MIC2203

can be synchronized to an external clock, or multiple

MIC2203s can easily be daisy-chained with the

SYNCLOCK feature.

The MIC2203 has a high loop bandwidth with

corresponding ultra fast transient response times.

This reduces the output capacitor size, and is very

useful when powering applications that require fast

dynamic response such as CPU cores and RF

circuitry in high performance cellular phones and

PDAs.

The MIC2203 is available in 10-pin MSOP and

3mm x 3mm MLF™-10L package options with an

operating junction temperature range from –40ºC to

125ºC.

Features

• Input voltage range: 2.3V to 5.5V

• Output voltage adjustable down to 0.5V

• 300mA output current

• Constant 1MHz PWM switching frequency

• > 95% efficiency

• < 1mA switching supply current

• < 350µA static quiescent current

• < 1µA shutdown current

• All-ceramic capacitors

• Easily synchronized to external clock

• SYNCLOCK feature to daisy chain multiple

devices

• Thermal shutdown and current limit protection

• 10 pin MSOP, and 3mm x 3mm MLF-10L package

options

• –40ºC to +125ºC junction temperature range

Applications

• 802.11 WLAN modules

• MD players

• MP3 players

_____________________________________________________________________

Typical Application

10nF

10µH

1µF

3.83k

10k 2.2µFSYNC_IN

SYNC_OUT

2.3V to 5.5V

1.8V

300mA

MIC2203BMM

High Efficiency Buck Regulator

MicroLead Frame and MLF are trademarks of Amkor Technologies.

Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax +1 (408) 474-1000 • http://www.micrel.com

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Ordering Information

Part Number

Standard Pb-Free

Output Voltage Junction Temperature

Range

Package

MIC2203BMM MIC2203YMM Adjustable -40°C to +125°C MSOP-10L

MIC2203BML MIC2203YML Adjustable -40°C to +125°C 3mm x 3mm MLF-10L

Pin Configuration

MSOP-10 (MM)

MLF-10 (ML)

Top View

Pin Description

Pin Number Pin Name Pin Function

1 SW Switch (Output): Internal power MOSFET output switches.

2 VIN Supply Voltage (Input): Requires a bypass capacitor to GND.

3 SYNC_IN

SYNC_IN for the MIC2203, Sync the main switching frequency to a external

clock. Should be tied to ground when not in use.

4 SYNC_OUT SYNC_OUT a 50ns wide sync pulse to feed into SYNC_IN on MIC2203.

Can be left open or tied to ground when not used.

5 EN

A low level EN will power down the device, reducing the quiescent current to

under 1µA.

6 FB

Input to the error amplifier, connect to the external resistor divider network to set

the output voltage.

7 BIAS

Internal circuit bias supply, nominally 2.3V. Must be de-coupled to signal ground

and can have a minimum of external DC loading.

8,9,10 GND Ground

EP GND Exposed backside pad, connect to Ground (MLF option only)

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Absolute Maximum Ratings

(1)

Supply Voltage (V

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

Output Switch Voltage (V

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

Logic Input Voltage (V

, V

SYNC_IN

) .............V

to –3V

Power Dissipation ............................................Note 5

Storage Temperature (T

)............... –65°C to +150°C

ESD Rating

(3)

........................................................2kV

Operating Ratings

(2)

Supply Voltage (V

)................................2.3V to 5.5V

Junction Temperature Range ......... –40°C to +125°C

Package Thermal Resistance

MSOP-10L (θ

)..................................... 115°C/W

3mmX3mm MLF-10L (θ

)....................... 60°C/W

Electrical Characteristics

(4)

= 25°C with V

= V

= 3.5V, unless otherwise specified. Bold values indicate –40ºC < T

< +125ºC

Parameter Condition Min Typ Max Units

Supply Voltage Range 2.3 5.5

= 0.6V (not switching) 320 450 µA

Quiescent Current

EN = 0V (shutdown) 0.01 1 µA

No Load Supply Current (switching) 870 µA

MIC2203 [Adjustable]

Feedback Voltage

0.4875 0.5 0.5125 V

Output Voltage Line

Regulation

OUT

< 2V; V

= 2.3V to 5.5V, I

LOAD

= 50mA

0.13 0.5 %

Output Voltage Load

Regulation

0mA < I

LOAD

< 300mA 0.2 0.5 %

Bias Regulator Output

Voltage

2.2 2.32 2.6 V

Maximum Duty Cycle V

≤ 0.4V 100 %

Current Limit V

= 0.4V 0.375 0.6 1.5 A

Switch ON-Resistance I

= 300mA V

= 0.4V

= -300mA V

= 0.6V

1.5

2.2

1.6

Ω

Enable Input Current 0.01 2 µA

Sync Frequency Range 0.8 1.25 MHz

SYNC_IN Threshold 0.7 1 1.7 V

Sync Minimum Pulse

Width

10 ns

SYNC_IN Input Current

1 µA

Oscillator Frequency 0.8 1 1.2 MHz

Enable Threshold 0.5 0.7 1.3 V

Enable Hysteresis 20 mV

Over Temperature

Shutdown Hysteresis

160

°C

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.

5. Absolute maximum power dissipation is limited by maximum junction temperature where P

D(MAX)

= (T

J(MAX)

– T

) ÷

JA.

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Typical Characteristics

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Functional Diagram

Internal

Supply

Oscillator

Ramp

Generator

Driver

PWM

Comparator

MIC2203

Error

Amplifier

0.5V

FB GND

VIN

SYNC_OUT

OUT

SYNC_IN

BIAS

Figure 1. MIC2203 Block Diagram

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Functional Description

provides power to the output and to the internal

bias supply. The supply voltage range is from 2.3V

to 5.5V. A minimum 1µF ceramic capacitor is

recommended for bypassing the input supply.

Enable

The enable pin provides a logic level control of the

output. In the off state, supply current of the device

is greatly reduced (typically <1µA). Also, in the off

state, the output drive is placed in a “tri-stated”

condition, where both the high side P-Channel

MOSFET and the low-side N-Channel are in an off

or non-conducting state. Do not drive the enable pin

above the supply voltage.

SYNC_IN

SYNC_IN pin enables the ability to change the

fundamental switching frequency. The SYNC_IN

frequency has a minimum frequency of 800KHz and

a maximum sync frequency of 1.2MHz. Careful

attention should be paid to not driving the SYNC_IN

pin greater than the supply voltage. Although this will

not damage the device, it can cause improper

operation.

SYNC_OUT

SYNC_OUT is an open collector output that

provides a signal equal to the internal oscillator

frequency. This creates the ability for multiple

MIC2203s to be connected together in a master-

slave configuration for frequency matching of the

converters. A typical 10kΩ resistor is recommended

for the pull-up resistor.

Bias

The bias supply is an internal 2.3V linear regulator

that supplies the internal biasing voltage to the

MIC2203. A 10nF ceramic capacitor is required on

this pin for bypassing. Do not use the bias pin as a

supply. The bias pin was designed to supply internal

power only.

Feedback

The feedback pin provides the control path to control

the output. A resistor divider connecting the

feedback to the output is used to adjust the desired

output voltage. Refer to the feedback section in the

“Applications Information” for more detail.

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Application Information

Input Capacitor

A minimum 1µF ceramic capacitor is recommended

on the V

pin for bypassing. X5R or X7R dielectrics

are recommended for the input capacitor. Y5V

dielectrics, aside from losing most of their

capacitance over temperature, also become resis-

tive at high frequencies. This reduces their ability to

filter out high frequency noise.

Output Capacitor

The MIC2203 was designed specifically for the use

of a 2.2µF ceramic output capacitor. Since the

MIC2203 is voltage mode regulator, the control loop

relies on the inductor and output capacitor for

compensation. For this reason, do not use

excessively large output capacitors. The output

capacitor requires either an X7R or X5R dielectric.

Y5V and Z5U dielectric capacitors, aside from the

undesirable effect of their wide variation in

capacitance over temperature, become resistive at

high frequencies. Using Y5V or Z5U capacitors will

cause instability in the MIC2203.

Total output capacitance should not exceed 3µF.

Inductor Selection

Inductor selection will be determined by the following

(not necessarily in the order of importance):

• Inductance

• Rated current value

• Size requirements

• DC resistance (DCR)

The MIC2203 is designed for use with a 10µH

inductor.

Maximum current ratings of the inductor are

generally given in two methods: permissible DC

current and saturation current. Permissible DC

current can be rated either for a 40°C temperature

rise or a 10% loss in inductance. Ensure the inductor

selected can handle the maximum operating current.

When saturation current is specified, make sure that

there is enough margin that the peak current will not

saturate the inductor.

The size requirements refer to the area and height

requirements that are necessary to fit a particular

design. Please refer to the inductor dimensions on

their datasheet.

DC resistance is also important. While DCR is

inversely proportional to size, DCR can represent a

significant efficiency loss. Refer to the “Efficiency

Considerations” below for a more detailed

description.

Bias Capacitor

A small 10nF ceramic capacitor is required to

bypass the bias pin. The use of low ESR ceramics

provides improved filtering for the bias supply.

Efficiency Considerations

Efficiency is defined as the amount of useful output

power, divided by the amount of power consumed.

Efficiency% =V

OUT ×IOUT

IN ×IIN

⎛

⎝

⎜

⎞

⎠

⎟ ×100

Maintaining high efficiency serves two purposes. It

reduces power dissipation in the power supply,

reducing the need for heat sinks and thermal design

considerations, and it reduces consumption of

current for battery powered applications. Reduced

current drawn from a battery increases the device’s

operating time, which is critical in hand held devices.

There are two loss terms in switching converters: DC

losses and switching losses. DC losses are simply

the power dissipation of I

R. Power is dissipated in

the high side switch during the on cycle. Power loss

is equal to the high side MOSFET R

DS(ON)

multiplied

by the (Switch Current)

. During the off cycle, the

low side N-Channel MOSFET conducts, also

dissipating power. Device operating current also

reduces efficiency. The product of the quiescent

(operating) current and the supply voltage is another

DC loss. The current required to drive the gates on

and off at a constant 1MHz frequency and the

switching transitions make up the switching losses.

Figure 2 shows an efficiency curve. The non-shaded

portion, from 0mA to 100mA, efficiency losses are

dominated by quiescent current losses, gate drive

and transition losses. In this case, lower supply

voltages yield greater efficiency in that they require

less current to drive the MOSFETs and have

reduced input power consumption.

Figure 2. Efficiency Curve

The shaded region, 100mA to 300mA, efficiency

loss is dominated by MOSFET R

DS(ON)

and inductor

DC losses. Higher input supply voltages will increase

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the Gate-to-Source threshold on the internal

MOSFETs, reducing the internal R

DS(ON)

. This

improves efficiency by reducing DC losses in the

device. All but the inductor losses are inherent to the

device. In which case, inductor selection becomes

increasingly critical in efficiency calculations. As the

inductors are reduced in size, the DC resistance

(DCR) can become quite significant. The DCR

losses can be calculated as follows:

OUT

×DCR

From that, the loss in efficiency due to inductor

resistance can be calculated as follows:

Efficiency Loss = -1 V

OUT

×I

OUT

×I

OUT

×P

⎛

⎝

⎜ ⎞

⎠

⎟

⎡

⎣

⎢

⎤

⎦

⎥ ×100

Efficiency loss, due to DCR, is minimal at light loads

and gains significance as the load is increased.

Inductor selection becomes a trade-off between

efficiency and size in this case.

Compensation

The MIC2203 is an internally compensated, voltage

mode buck regulator. Voltage mode is achieved by

creating an internal 1MHz ramp signal and using the

output of the error amplifier to pulse width modulate

the switch node, maintaining output voltage

regulation. With a typical gain bandwidth of 100kHz,

the MIC2203 is capable of extremely fast transient

responses.

The MIC2203 is designed to be stable with a 10µH

inductor and a 2.2µF ceramic (X5R) output

capacitor.

Feedback

The MIC2203 provides a feedback pin to adjust the

output voltage to the desired level. This pin connects

internally to an error amplifier. The error amplifier

then compares the voltage at the feedback to the

internal 0.5V reference voltage and adjusts the

output voltage to maintain regulation. To calculate

the resistor divider network for the desired output is

as follows:

R2 =R1

OUT

REF

−1

⎛

⎝

⎜ ⎞

⎠

⎟

Where V

REF

is 0.5V and V

OUT

is the desired output

voltage. A 10kΩ or lower resistor value from the

output to the feedback is recommended. Larger

resistor values require an additional capacitor (feed-

forward) from the output to the feedback. The large

high side resistor value and the parasitic

capacitance on the feedback pin (~10pF) can cause

an additional pole in the loop. The additional pole

can create a phase loss at high frequency. This

phase loss degrades transient response by reducing

phase margin. Adding feed-forward capacitance

negates the parasitic capacitive effects of the

feedback pin.

Also, large feedback resistor values increase the

impedance, making the feedback node more

susceptible to noise pick-up. A feed-forward

capacitor would also reduce noise pick-up by

providing a low impedance path to the output.

PWM Operation

The MIC2203 is a pulse width modulation (PWM)

regulator. By controlling the ratio of on-to-off time, or

duty cycle, a regulated DC output voltage is

achieved. As load or supply voltage changes, so

does the duty cycle to maintain a constant output

voltage. In cases where the input supply runs into a

dropout condition, the MIC2203 will run at 100%

duty cycle.

The MIC2203 provides constant switching at 1MHz

with synchronous internal MOSFETs. The internal

MOSFETs include a high-side P-Channel MOSFET

from the input supply to the switch pin and an N-

Channel MOSFET from the switch pin-to-ground.

Since the low-side N-Channel MOSFET provides the

current during the off cycle, a free wheeling Schottky

diode from the switch node to ground is not required.

PWM control provides fixed frequency operation. By

maintaining a constant switching frequency,

predictable fundamental and harmonic frequencies

are achieved. Other methods of regulation, such as

burst and skip modes, have frequency spectrums

that change with load that can interfere with

sensitive communication equipment.

Synchronization

SYNC_IN allows the user to change the frequency

from 1MHz up to 1.25MHz or down to 800KHz. This

allows the ability to control the fundamental

frequency and all the resultant harmonics.

Maintaining a predictable frequency creates the

ability to either shift the harmonics away from

sensitive carrier and IF frequency bands or to

accurately filter out specific harmonic frequencies.

The SYNC_OUT function pin allows for the ability to

be able to sync up multiple MIC2203s in a “daisy-

chain”, connecting SYNC_OUT to SYNC_IN of the

other MIC2203. Synchronizing multiple MIC2203s

benefits much in the same way as syncing up one

MIC2203. All regulators will run at the same funda-

mental frequency, resulting in matched harmonic

frequencies, simplifying design for sensitive

communication equipment.

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MIC2203

Figure 1. Master-Slave Operation

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MIC2203

MIC2203 with 10µH Inductor and 2.2µF Output Capacitor

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MIC2203

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MIC2203

MIC2203BMM Evaluation Board Schematic

Figure 2. MIC2203BMM Evaluation Board Schematic

Bill of Materials

Item Part Number Manufacturer Description

06036D105MAT AVX 1µF Ceramic Capacitor X5R, 6.3V, Size 0603

GRM185R60J105KE21D Murata 1µF Ceramic Capacitor X5R, 6.3V, Size 0603

0201ZD103MAT2 AVX 10nF Ceramic Capacitor 6.3V, Size 0201 C2

GRM033R10J103KA01D Murata 10nF Ceramic Capacitor 6.3V, Size 0202

06036D225MAT AVX 2.2µF Ceramic Capacitor X5R, 6.3V, Size 0603

GRM185R60J22SKE21D Murata 2.2µF Ceramic Capacitor X5R, 6.3V, Size 0603

LQH32CN100M Murata 10µH Inductor

CDRH2D14-10 Sumida 10µH Inductor

R1 CRCW04021002F Vishay-Dale 10kΩ 1%, Size 0402

R2 CRCW04021781F

CRCW04022491F

CRCW04023831F

CRCW04024991F

CRCW04027151F

CRCW04021002F

Vishay-Dale

1.78kΩ 1%, Size 0402 For 3.3V

OUT

2.49kΩ 1%, Size 0402 For 2.5V

OUT

3.83kΩ 1%, Size 0402 For 1.8V

OUT

4.99kΩ 1%, Size 0402 For 1.5V

OUT

7.15kΩ 1%, Size 0402 For 1.2V

OUT

10kΩ 1%, Size 0402 For 1V

OUT

Open For 0.5V

OUT

U1 MIC2203BMM Micrel, Inc. 1MHz High Efficiency Synchronous Buck Regulator

Notes:

1. AVX: www.avx.com

2. Murata: www.murata.com

3. Sumida: www.sumida.com

4. Vishay-Dale: www.vishay.com

5. Micrel, Inc: www.micrel.com

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MIC2203

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Package Information

10-Pin MSOP (MM)

10-Pin MLF™ (ML)

MICREL, INC. 2180 Fortune DRIVE SAN JOSE, CA 95131 USA

TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com

The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel

for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.

Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a

product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended

for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a

significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a

Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale.