MIC47300WD TR - MICROCHIP TECHNOLOGY

MIC47300

3A, Low Voltage, Adjustable LDO

Regulator with Dual Input Supply

*See Thermal Design Section

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

October 2009 M9999-102309-A

General Description

The MIC47300 is a high-bandwidth, low-dropout, 3A volt-

age regulator ideal for powering core voltages of low-

power microprocessors. The MIC47300 implements a dual

supply conﬁguration allowing for very low output

impedance and very fast transient response.

The MIC47300 requires a bias input supply between 3V

and 6.5V for proper operation. The main input supply rail

operates from 1.4V to 6.5V that allows for adjustable

output voltages down to 0.9V.

The MIC47300 requires a minimum of 1µF output

capacitance for stability, and optimal operation is achieved

with small ceramic capacitors.

The MIC47300 is available in a 5-pin power D-Pak

package (TO-252) with an operating temperature range of

–40°C to +125°C.

Datasheets and support documentation can be found on

Micrel’s web site at: www.micrel.com.

Features

• Input Voltage Range:

– VIN: 1.4V to 6.5V

– VBIAS: 3.0V to 6.5V

• Stable with 1µF ceramic capacitor

• ±1% initial tolerance

• Maximum dropout voltage (VIN–VOUT) of 400mV

over temperature

• Adjustable output voltage down to 0.9V

• Ultra fast transient response (Up to 10MHz bandwidth)

• Excellent line and load regulation specifications

• Power D-Pak package (TO-252)

• Thermal shutdown and current-limit protection

• Junction temperature range: –40°C to 125°C

Applications

• Graphics processors

• PC add-in cards

• Microprocessor core voltage supply

• Low voltage digital ICs

• High efficiency linear power supplies

• SMPS post regulators

__________________________________________________________________________________________

Typical Application*

Figure 1. Typical Application Circuit

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Ordering Information

Part Number Output Current Voltage Junction Temp. Range Package

MIC47300WD* 3A Adjustable –40° to +125°C 5-Pin TO-252

Note:

* RoHs compliant with ‘high-melting solder’ exemption.

Pin Configur ation

5-Pin TO-252 D-Pak (D)

Pin Description

Pin Number Pin Name Pin Name

1 ADJ

Adjustable Regulator Feedback Input: Connect to the resistor voltage divider that is

placed from OUT to GND in order to set the output voltage.

2 BIAS

Input Bias Voltage: Voltage for powering all internal circuitry of the regulator with the

exception of the output power device.

3 GND, TAB Ground: TAB is also connected internally to the IC’s ground on D-Pak.

4 IN Input Voltage: Supplies the current to the output power device

5 OUT

Regulator Output: The output voltage is set by the resistor divider connected from OUT

to GND (with the divided connection tied to ADJ). A minimum value capacitor must be

used to maintain stability. See Applications Information.

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Absolute Maximum Ratings(1)

Supply Voltage (VIN).........................................................8V

Bias Supply Voltage (VBIAS)..............................................8V

Power Dissipation .....................................Internally Limited

ESD Rating(3).................................................................. 2kV

Operating Ratings(2)

Supply Voltage (VIN)......................................... 1.4V to 6.5V

Bias Supply Voltage (VBIAS)................................. 3V to 6.5V

Junction Temperature (TJ) ..................–40°C ≤ TJ ≤ +125°C

Maximum Power Dissipation..................................... Note 4

Package Thermal Resistance

TO-252 (θJC) ........................................................3°C/W

TO-252 (θJA).......................................................56°C/W

Electrical Characteristics(5)

VIN = VOUT + 1V, VBIAS = VOUT + 2.1V, IOUT = 10mA; TA = 25°C, bold values indicate –40°C≤ TJ ≤ +125°C, unless noted.

Symbol Parameter Condition Min Typ Max Units

VLNREG Line Regulation VIN = VOUT +1V to 6.5V –0.1 0.01 +0.1 %/V

VLDREG Load Regulation IOUT = 10mA to A 0.2 0.5 %

VDO Dropout Voltage (VIN -VOUT) IOUT = 1.5A

IOUT = 3A

105

230

200

400 mV

VDO(BIAS) Dropout Voltage (VBIAS - VOUT)

Note 6 IOUT = 3A

1.24

2.1 V

IGND Ground Pin Current, Note 7 IOUT = 10mA

IOUT = 3A

50 mA

IBIAS Current thru VBIAS I

OUT = 10mA

IOUT = 3A

150

ILIM Current Limit VOUT = 0V 6.5 10 A

Thermal Shutdown 168 °C TSD

Thermal Shutdown Hysteresis 10 °C

Reference (Adjust Pin)

VADJ Reference Voltage 0.891

0.882

0.9 0.909

0.918

IADJ Adjust Pin Current VADJ = 1.2V 0.01 1 μA

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. PD(MAX) = (TJ(MAX) – TA) / θJA, where θJA, depends upon the printed circuit layout. See “Applications Information.”

5. Specification for packaged product only.

6. For VOUT ≤1V, VBIAS dropout speciﬁcation does not apply due to a minimum 3V VBIAS input.

7. IGND = IBIAS + (IIN – IOUT). At high loads, input current on VIN will be less than the output current, due to drive current being supplied by VBIAS.

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Typical Characteristics

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Typical Characteristics (continued)

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Functional Characteristics

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Functional Description

The MIC47300 is an ultra-high performance, low-dropout

linear regulator designed for high current applications

requiring fast transient response. The MIC47300 utilizes

two input supplies, signiﬁcantly reducing dropout

voltage, perfect for low-voltage, DC-to-DC conversion.

The MIC47300 requires a minimum of external

components and obtains a bandwidth of up to 10MHz.

As a µCap regulator, the output is tolerant of virtually

any type of capacitor including ceramic type and

tantalum type capacitors.

The MIC47300 regulator is fully protected from damage

due to fault conditions, offering linear current limiting and

thermal shutdown.

Bias Supply Voltage

VBIAS, requiring relatively light current, provides power to

the control portion of the MIC47300. VBIAS requires

approximately 50mA for a 3A load current. Dropout

conditions require higher currents. Most of the biasing

current is used to supply the base current to the pass

transistor. This allows the pass element to be driven into

saturation, reducing the dropout to 230mV at a 3A load

current. Bypassing on the bias pin is recommended to

improve performance of the regulator during line and

load transients. Small ceramic capacitors from VBIAS to

ground help reduce high frequency noise from being

injected into the control circuitry from the bias rail and

are good design practice. Good bypass techniques

typically include one larger capacitor such as 1µF

ceramic and smaller valued capacitors such as 0.01µF

or 0.001µF in parallel with that larger capacitor to

decouple the bias supply. The VBIAS input voltage must

be 2.1V above the output voltage with a minimum VBIAS

inpt voltage of 3 volts.

Input Supply Voltage

VIN provides the high current to the collector of the pass

transistor. The minimum input voltage is 1.4V, allowing

conversion from low voltage supplies.

Output Capacitor

The MIC47300 is designed to be stable with a minimal

capacitance value and without ESR constraints.

However, proper capacitor selection is important to

ensure desired transient response. A 1µF ceramic chip

capacitor should satisfy most applications and output

capacitance can be increased without bound. See

“Typical Characteristic” for examples of load transient

response.

X7R dielectric ceramic capacitors are recommended

because of their temperature performance. X7R-type

capacitors change capacitance by 15% over their

operating temperature range and are the most stable

type of ceramic capacitors. Z5U and Y5V dielectric

capacitors change value by as much as 50% and 60%

respectively over their operating temperature ranges. To

use a ceramic chip capacitor with Y5V dielectric, the

value must be much higher than an X7R ceramic or a

tantalum capacitor to ensure the same capacitance

value over the operating temperature range. Tantalum

capacitors have a very stable dielectric (10% over their

operating temperature range) and can also be used with

this device.

Input Capacitor

Additional bypass capacitance is recommended when

the device is more than 2 to 3 inches away from the bulk

supply capacitance, or when the supply is a battery.

Small, surface-mount, ceramic chip capacitors can be

used for the bypassing. A 1μF or greater ceramic input

capacitor should be placed next to the device for optimal

performance. Larger values will help to improve ripple

rejection by bypassing the input to the regulator, further

improving the integrity of the output voltage.

Thermal Design

Linear regulators are simple to use. The most

complicated design parameters to consider are thermal

characteristics. Thermal design requires the following

application-speciﬁc parameters:

• Maximum ambient temperature (TA)

• Output current (IOUT)

• Output voltage (VOUT)

• Input voltage (VIN)

• Ground current (IGND)

First, calculate the power dissipation of the regulator

from these numbers and the device parameters from this

datasheet.

D = VIN × IIN + VBIAS × IBIAS – VOUT × IOUT

The input current will be less than the output current at

high output currents as the load increases. The bias

current is a sum of base drive and ground current.

Ground current is constant over load current. Then the

heat sink thermal resistance is determined with this

formula:

()

CSJC

AJ(MAX)

SA θθ

θ+−

⎟

⎠

⎞

⎜

⎝

⎛−

The heat sink may be signiﬁcantly reduced in

applications where the maximum input voltage is known

and large compared with the dropout voltage. Use a

series input resistor to drop excessive voltage and

distribute the heat between this resistor and the

regulator. The low-dropout properties of the MIC47300

allow signiﬁcant reductions in regulator power dissipation

and the associated heat sink without compromising

performance. When this technique is employed, a

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capacitor of at least 1µF is needed directly between the

input and regulator ground. Refer to “Application Note 9”

for further details and examples on thermal design and

heat sink speciﬁcation.

The maximum power allowed can be calculated using

the thermal resistance (θJA) of the D-Pak adhering to the

following criteria for the PCB design: 2 oz. copper and

100mm2 copper area for the MIC47300. Given a

maximum ambient temperature (TA=75°C), and without

the use of a heat sink, the maximum power allowed that

would not exceed the IC’s maximum junction

temperature (125°C) is

PD(MAX) = (TJ(MAX) – TA)/θJA = (125°C – 75°C)/(56°C/W)

= 0.893W

Minimum Load Current

The MIC47300, unlike most other high current

regulators, does not require a minimum load to maintain

output voltage regulation.

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Application Information

Adjustable Regulator Design

The MIC47300 allows programming the output down to

0.9V. From the typical application in Figure 1, the output

voltage is set by placing a resistor divider network from

OUT to GND and is determined by the following

equation:

⎟

⎠

⎞

⎜

⎝

⎛+×= 1

0.9VOUT

where VOUT is the desired output voltage.

The resistor value between VOUT and the adjust pin

should not exceed 10kΩ. Larger values can cause

instability. The resistor values are calculated from the

above equation, resulting in the following:

⎟

⎠

⎞

⎜

⎝

⎛−×= 1

0.9

R2R1 OUT

Evaluation Board Layout

The MIC47300 evaluation board layout is shown in

Figures 2 and 3. For customer application boards,

recommended variations include using a static resistor

for R2 in place of the potentiometer as well as the

elimination of all test points and jumper options that are

included on the MIC47300 evaluation board.

Figure 2. MIC47300 EVB Top Layer

Figure 3. MIC47300 EVB Bottom Layer

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Evaluation Board

Bill of Materials

Item Part Number Manufacturer Description Qty.

C1 C1206C106K8RACTU Kemet(1) 10µF, 10V, X7R Ceramic Capacitor 1

C2 C0805C105K8RACTU Kemet 1µF, 10V, X7R Ceramic Capacitor 1

C3 C0805C105K8RACTU Kemet 1µF, 10V, X7R Ceramic Capacitor 1

R1 CRCW08051800F Vishay(2) 180Ω Resistor, Film, 0805 1

R2 PV36W502C01B00 Murata(3) 5kΩ Potentiometer 1

U1 MIC47300WD Micrel, Inc.(4) MIC47300 LDO Regulato r 1

Notes:

1. Kemet: www.kemet.com

2. Vishay: www.vishay.com

3. Murata: www.murata.com

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

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Package Information

5-Pin TO-252 Power D-Pak (D)

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.

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