MIC23031-AYMTTR - Micrel, Inc. - Datasheet.Directory

MIC23031

4MHz PWM 400mA Buck Regulator with

HyperLight Load™

HyperLight Load is a trademark of Micrel, Inc

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

General Description

The MIC23031 is a high-efficiency 4MHz 400mA

synchronous buck regulator with HyperLight Load™ mode.

HyperLight Load™ provides very-high efficiency at light

loads and ultra-fast transient response which is perfectly

suited for supplying processor core voltages. An additional

benefit of this proprietary architecture is very-low output

ripple voltage throughout the entire load range with the use

of small output capacitors. The tiny 1.6mm x 1.6mm Thin

MLF® package saves precious board space and requires

only three external components.

The MIC23031 is designed for use with a very-small

inductor, down to 0.47µH, and an output capacitor as small

as 2.2µF that enables a sub-1mm height.

The MIC23031 has a very-low quiescent current of 21µA

and achieves as high as 88% efficiency at 1mA. At higher

loads, the MIC23031 provides a constant switching

frequency around 4MHz while achieving peak efficiencies

up to 93%.

The MIC23031 is available in a 6-pin 1.6mm x 1.6mm Thin

MLF® package with an operating 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: 2.7V to 5.5V

• 400mA output current

• Up to 93% efficiency and 88% at 1mA

• 21µA typical quiescent current

• 4MHz PWM operation in continuous mode

• Ultra-fast transient response

• Low voltage output ripple

– 20mVpp ripple in HyperLight Load™ mode

– 3mV output voltage ripple in full PWM mode

• 0.01µA shutdown current

• Fixed and adjustable output voltage options available

• 6-pin 1.6mm x 1.6mm Thin MLF®

• –40°C to +125°C junction temperature range

Applications

• Mobile handsets

• Portable media/MP3 players

• Portable navigation devices (GPS)

• WiFi/WiMax/WiBro modules

• Digital Cameras

• Wireless LAN cards

• USB-powered devices

• Portable applications

Typical Application

October 2010 M9999-102210-A

Micrel Inc. MIC23031

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Ordering Information

Part Number Marking

Code Nominal

Output Voltage Junction

Temperature Range Package Lead Finish

MIC23031-AYMT GEA Adjustable −40°C to +125°C 6-Pin 1.6mm × 1.6mm Thin MLF® Pb-Free

MIC23031-GYMT GEG 1.8V −40°C to +125°C 6-Pin 1.6mm × 1.6mm Thin MLF® Pb-Free

MIC23031-FYMT GEF 1.5V −40°C to +125°C 6-Pin 1.6mm × 1.6mm Thin MLF® Pb-Free

MIC23031-4YMT GE4 1.2V −40°C to +125°C 6-Pin 1.6mm × 1.6mm Thin MLF® Pb-Free

MIC23031-CYMT GEC 1.0V −40°C to +125°C 6-Pin 1.6mm × 1.6mm Thin MLF® Pb-Free

Notes:

1. Other options available. Contact Micrel for details.

2. Thin MLF® is GREEN RoHS-compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.

Pin Configur ation

1VIN

SNS

PGND

AGND

3 4

1VIN

SNS

GND

3 4

6-Pin 1.6 x 1.6mm Thin MLF ® (MT)

Fixed (Top View) 6-Pin 1.6 x 1.6mm Thin MLF ® (MT)

Adjustable (Top View)

Pin Description

Fixed

Option Adjustable

Option Pin Name Pin Function

1 1 VIN Input Voltage: Connect a capacitor to ground to decouple the noise.

2 2 SW Switch (Output): Internal power MOSFET output switches.

3 3 SNS

Sense: Connect to VOUT as close to output capacitor as possible to sense output

voltage.

4 4 EN

Enable (Input): Logic high enables operation of the regulator. Logic low will shut down

the device. Do not leave floating.

5 − AGND Analog Ground: Connect to central ground point where all high current paths meet

(CIN, COUT, PGND) for best operation.

− 5 FB

Feedback (Input): Connect resistor divider at this node to set output voltage. Resistors

should be selected based on a nominal VFB of 0.62V.

6 − PGND Power Ground.

− 6 GND Ground.

ePad ePad HS PAD Connect to PGND or GND.

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Absolute Maximum Ratings(1)

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

Sense (VSNS).. ..................................................................6V

Output Switch Voltage ..................................................6V

Enable Input Voltage (VEN)................................−0.3V to VIN

Storage Temperature Range ..……………−65°C to +150°C

ESD Rating(3)................................................. ESD Sensitive

Operating Ratings(2)

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

Enable Input Voltage (VEN) .. ……………………….0V to VIN

Output Voltage Range (VSNS) ………………….0.7V to 3.6V

Junction Temperature Range (TJ).. ….−40°C ≤ TJ ≤ +125°C

Thermal Resistance

1.6 x 1.6mm Thin MLF®-6 (θJA).......................92.4°C/W

Electrical Characteristics(4)

TA = 25°C; VIN = VEN = 3.6V; L = 1µH; COUT = 4.7µF unless otherwise specified.

Bold values indicate –40°C  TJ  +125°C, unless noted.

Parameter Condition Min. Typ. Max. Units

Supply Voltage Range 2.7 5.5 V

Under-Voltage Lockout Threshold (Turn-on) 2.45 2.55 2.65 V

Quiescent Current IOUT = 0mA , SNS > 1.2 * VOUT Nominal 21 35 µA

Shutdown Current VEN = 0V, VIN = 5.5V 0.01 4 µA

Output Voltage Accuracy VIN = 3.6V; ILOAD = 20mA −2.5 +2.5

Feedback Voltage Adjustable Option Only 0.62 V

Current Limit SNS = 0.9*VOUTNOM 0.41 0.7 1 A

Output Voltage Line Regulation VIN = 3.0V to 5.5V, VOUT = 1.2V, ILOAD = 20mA, 0.3 %/V

Output Voltage Load Regulation 20mA < ILOAD < 400mA, VOUT = 1.2V,

VIN = 3.6V 0.7 %

PWM Switch ON-Resistance ISW = 100mA PMOS

ISW = −100mA NMOS 0.65

0.8 

Frequency IOUT = 120mA 4 MHz

Soft-Start Time VOUT = 90% 100 µs

Enable Threshold 0.5 0.9 1.2 V

Enable Input Current 0.1 2 µA

Over-Temperature Shutdown

160 °C

Over-Temperature Shutdown Hysteresis 20 °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.

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Typical Characteristics

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Typical Characteristics (Continued)

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Functional Characteristics

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Functional Characteristics (Continued)

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Functional Characteristics (Continued)

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Functional Diagram

VIN

PGND

SNS

AGND

UVLO

Reference

ISENSE

Gate

Drive

ERROR

COMPARATOR

CONTROL

LOGIC

Timer &

Softstart

ZERO 1

Current

Limit

Simplified MIC23031 Fixed Functional Block Diagram

VIN

SNS

GND

UVLO

Reference

ISENSE

Gate

Drive

ERROR

COMPARATOR

CONTROL

LOGIC

Timer &

Softstart

ZERO 1

Current

Limit

Simplified MIC23031 Adjustable Functional Block Diagram

Micrel, Inc. MIC23031

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Functional Description

VIN

The input supply (VIN) provides power to the internal

MOSFETs for the switch mode regulator along with the

internal control circuitry. The VIN operating range is 2.7V

to 5.5V so an input capacitor, with a minimum voltage

rating of 6.3V, is recommended. Due to the high

switching speed, a minimum 2.2µF bypass capacitor

placed close to VIN and the power ground (PGND) pin is

required. Refer to the layout recommendations for

details.

A logic high signal on the enable pin activates the output

voltage of the device. A logic low signal on the enable

pin deactivates the output and reduces supply current to

0.01µA. MIC23031 features built-in soft-start circuitry

that reduces in-rush current and prevents the output

voltage from overshooting at start up. Do not leave

floating.

The switch (SW) connects directly to one end of the

inductor and provides the current path during switching

cycles. The other end of the inductor is connected to the

load, SNS pin and output capacitor. Due to the high

speed switching on this pin, the switch node should be

routed away from sensitive nodes whenever possible.

SNS

The sense (SNS) pin is connected to the output of the

device to provide feedback to the control circuitry. The

SNS connection should be placed close to the output

capacitor. Refer to the layout recommendations for more

details.

AGND (Fixed Outpu t Only)

The analog ground (AGND) is the ground path for the

biasing and control circuitry. The current loop for the

signal ground should be separate from the power ground

(PGND) loop. Refer to the layout recommendations for

more details.

FB (Adjustable Output Only)

The feedback pin (FB) allows the regulated output

voltage to be set by applying an external resistor

network. The internal reference voltage is 0.62V and the

recommended value of R2 is 200kΩ. The output voltage

is calculated from the equation below.

⎟

⎠

⎞

⎜

⎝

⎛+= 1

kΩ200

V62.0VOUT

SNS

GND

MIC23031

VIN

IN VOUT

GND

Figure 1. MIC23031-AYMT Schematic

PGND / GND

The power ground pin is the ground path for the high

current in PWM mode. The current loop for the power

ground should be as small as possible and separate

from the analog ground (AGND) loop as applicable.

Refer to the layout recommendations for more details.

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Application Information

The MIC23031 is a high-performance DC/DC step-down

regulator offering a small solution size. Supporting an

output current up to 400mA inside a tiny 1.6mm x 1.6mm

Thin MLF® package and requiring only three external

components, the MIC23031 meets today’s miniature

portable electronic device needs. Using the HyperLight

Load™ switching scheme, the MIC23031 is able to

maintain high efficiency throughout the entire load range

while providing ultra-fast load transient response. The

following sections provide additional device application

information.

Input Capacitor

A 2.2µF ceramic capacitor or greater should be placed

close to the VIN pin and PGND / GND pin for bypassing.

A TDK C1608X5R0J475K, size 0603, 4.7µF ceramic

capacitor is recommended based upon performance,

size and cost. A X5R or X7R temperature rating is

recommended for the input capacitor. Y5V temperature

rating capacitors, aside from losing most of their

capacitance over temperature, can also become

resistive at high frequencies. This reduces their ability to

filter out high-frequency noise.

Output Capacitor

The MIC23031 was designed for use with a 2.2µF or

greater ceramic output capacitor. Increasing the output

capacitance will lower output ripple and improve load

transient response but could increase solution size or

cost. A low equivalent series resistance (ESR) ceramic

output capacitor such as the TDK C1608X5R0J475K,

size 0603, 4.7µF ceramic capacitor is recommended

based upon performance, size and cost. Both the X7R or

X5R temperature rating capacitors are recommended.

The Y5V and Z5U temperature rating capacitors are not

recommended due to their wide variation in capacitance

over temperature and increased resistance at high

frequencies.

Inductor Selection

When selecting an inductor, it is important to consider

the following factors (not necessarily in the order of

importance):

• Inductance

• Rated current value

• Size requirements

• DC resistance (DCR)

The MIC23031 was designed for use with an inductance

range from 0.47µH to 4.7µH. Typically, a 1µH inductor is

recommended for a balance of transient response,

efficiency and output ripple. For faster transient

response, a 0.47µH inductor will yield the best result. For

lower output ripple, a 4.7µH inductor is recommended.

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% to 20% 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 so

that the peak current does not cause the inductor to

saturate. Peak current can be calculated as follows:

⎥

⎦

⎤

⎢

⎣

⎡

⎟

⎠

⎞

⎜

⎝

⎛

××

−

+= Lf2

OUT

PEAK

As shown by the calculation above, the peak inductor

current is inversely proportional to the switching

frequency and the inductance; the lower the switching

frequency or the inductance the higher the peak current.

As input voltage increases, the peak current also

increases.

The size of the inductor depends on the requirements of

the application. Refer to Typical Application Circuit and

Bill of Materials for details.

DC resistance (DCR) is also important. While DCR is

inversely proportional to size, DCR can represent a

significant efficiency loss. Refer to the Efficiency

Considerations.

Compensation

The MIC23031 is designed to be stable with a 0.47µH to

4.7µH inductor with a minimum of 2.2µF ceramic (X5R)

output capacitor.

Duty Cycle

The typical maximum duty cycle of the MIC23031 is

80%.

Efficiency Considerations

Efficiency is defined as the amount of useful output

power, divided by the amount of power supplied.

100

OUT

%Efficiency ×

⎟

⎠

⎞

⎜

⎝

⎛

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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 draw

from a battery increases the devices operating time and

is critical in hand held devices.

There are two types of losses in switching converters;

DC losses and switching losses. DC losses are simply

the power dissipation of I2R. Power is dissipated in the

high side switch during the on cycle. Power loss is equal

to the high side MOSFET RDSON multiplied by the Switch

Current squared. 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 represents another DC loss. The current

required driving the gates on and off at a constant 4MHz

frequency and the switching transitions make up the

switching losses.

Figure 2. MIC23031 Efficiency Curve

The figure above shows an efficiency curve. From no

load to 100mA, efficiency losses are dominated by

quiescent current losses, gate drive and transition

losses. By using the HyperLight Load™ mode, the

MIC23031 is able to maintain high efficiency at low

output currents.

Over 100mA, efficiency loss is dominated by MOSFET

RDSON and inductor losses. Higher input supply voltages

will increase the Gate-to-Source threshold on the

internal MOSFETs, thereby reducing the internal RDSON.

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:

L Pd = IOUT

2 × DCR Eq. 3

From that, the loss in efficiency due to inductor

resistance can be calculated as follows:

100

OUT

%Efficiency ×

⎟

⎠

⎞

⎜

⎝

⎛

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.

HyperLight Load™ Mode

MIC23031 uses a minimum on and off time proprietary

control loop (patented by Micrel). When the output

voltage falls below the regulation threshold, the error

comparator begins a switching cycle that turns the

PMOS on and keeps it on for the duration of the

minimum-on-time. This increases the output voltage. If

the output voltage is over the regulation threshold, then

the error comparator turns the PMOS off for a minimum-

off-time until the output drops below the threshold. The

NMOS acts as an ideal rectifier that conducts when the

PMOS is off. Using a NMOS switch instead of a diode

allows for lower voltage drop across the switching device

when it is on. The asynchronous switching combination

between the PMOS and the NMOS allows the control

loop to work in discontinuous mode for light load

operations. In discontinuous mode, the MIC23031 works

in pulse frequency modulation (PFM) to regulate the

output. As the output current increases, the off-time

decreases, thus provides more energy to the output.

This switching scheme improves the efficiency of

MIC23031 during light load currents by only switching

when it is needed. As the load current increases, the

MIC23031 goes into continuous conduction mode (CCM)

and switches at a frequency centered at 4MHz. The

equation to calculate the load when the MIC23031 goes

into continuous conduction mode may be approximated

by the following formula:

(

)

⎟

⎠

⎞

⎜

⎝

⎛

=f 2L

OUT

V-

LOAD

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As shown in the previous equation, the load at which

MIC23031 transitions from HyperLight Load™ mode to

PWM mode is a function of the input voltage (VIN), output

voltage (VOUT), duty cycle (D), inductance (L) and

frequency (f). This is illustrated in the graph below. Since

the inductance range of MIC23031 is from 0.47µH to

4.7µH, the device may then be tailored to enter

HyperLight Load™ mode or PWM mode at a specific

load current by selecting the appropriate inductance. For

example, in Figure 3, when the inductance is 4.7µH the

MIC23031 will transition into PWM mode at a load of

approximately 4mA. Under the same condition, when the

inductance is 1µH, the MIC23031 will transition into

PWM mode at approximately 70mA.

Figure 3. MIC23031 SW Frequency vs. Output Current

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MIC23031 Typical Application Circuit (Fixed 1.8V)

SNS

PGND

GND

VOUT

AGND

U1 MIC23031

VIN

2.7 to 5.5V

GND

Bill of Materials

Item Part Number Manufacturer Description Qty.

C1, C2 C1608X5R0J475K TDK(1) 4.7µF Ceramic Capacitor, 6.3V, X5R, Size 0603 2

LQM21PN1R0M00 Murata(2) 1µH, 0.8A, 190m, L2mm x W1.25mm x H0.5mm

LQH32CN1R0M33 Murata(2) 1µH, 1A, 60m, L3.2mm x W2.5mm x H2.0mm

LQM31PN1R0M00 Murata(2) 1µH, 1.2A, 120m, L3.2mm x W1.6mm x H0.95mm

GLF251812T1R0M TDK(1) 1µH, 0.8A, 100m, L2.5mm x W1.8mm x H1.35mm

LQM31PNR47M00 Murata(2) 0.47µH, 1.4A, 80m, L3.2mm x W1.6mm x H0.85mm

MIPF2520D1R5 FDK(3) 1.5µH, 1.5A, 70m, L2.5mm x W2mm x H1.0mm

U1 MIC23031-xYMT Micrel, Inc.(4) 4MHz 400mA Buck Regulator with HyperLight Load™ Mode 1

Notes:

1. TDK: www.tdk.com.

2. Murata: www.murata.com.

3. FDK: www.fdk.co.jp.

4. Micrel, Inc.: www.micrel.com.

Micrel, Inc. MIC23031

October 2010 15 M9999-102210-A

MIC23031 Typical Application Circuit (Adjustable 1.8V)

SNS

GND

U1 - MIC23031

VIN

IN VOUT

GND

200k

383k

Bill of Materials

Item Part Number Manufacturer Description Qty.

C1, C2 C1608X5R0J475K TDK(1) 4.7µF Ceramic Capacitor, 6.3V, X5R, Size 0603 2

R1 CRCW06033833FT1 Vishay(2) 383k, 1%, Size 0603 1

R2 CRCW06032003FT1 Vishay(2) 200k, 1%, Size 0603 1

LQM21PN1R0M00 Murata(3) 1µH, 0.8A, 190m, L2mm x W1.25mm x H0.5mm

LQH32CN1R0M33 Murata(3) 1µH, 1A, 60m, L3.2mm x W2.5mm x H2.0mm

LQM31PN1R0M00 Murata(3) 1µH, 1.2A, 120m, L3.2mm x W1.6mm x H0.95mm

GLF251812T1R0M TDK(1) 1µH, 0.8A, 100m, L2.5mm x W1.8mm x H1.35mm

LQM31PNR47M00 Murata(3) 0.47µH, 1.4A, 80m, L3.2mm x W1.6mm x H0.85mm

MIPF2520D1R5 FDK(4) 1.5µH, 1.5A, 70m, L2.5mm x W2mm x H1.0mm

U1 MIC23031-AYMT Micrel, Inc.(5) 4MHz 400mA Buck Regulator with HyperLight Load™ Mode 1

Notes:

1. TDK: www.tdk.com.

2. Vishay: www.vishay.com.

3. Murata: www.murata.com.

4. FDK: www.fdk.co.jp.

5. Micrel, Inc.: www.micrel.com.

Micrel, Inc. MIC23031

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PCB Layout Recommendations (Fixed)

Fixed Top Layer

Fixed Bottom Layer

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October 2010 17 M9999-102210-A

PCB Layout Recommendations (Adjustable)

Adjustable Top Layer

Adjustable Bottom Layer

Micrel, Inc. MIC23031

October 2010 18 M9999-102210-A

Package Information

6-pin 1.6mm x 1.6mm Thin MLF® (MT)

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

Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This

information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,

specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual

property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability

whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties

relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right

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

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

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.

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