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November 2006 1 MIC29310/29312

MIC29310/29312 Micrel

General Description

The MIC29310 and MIC29312 are low cost versions of

MIC29300 family low-dropout (LDO) regulators. Manufac-

tured on Micrel’s proprietary Super beta PNP™ process,

the MIC29310/2 is a 3A LDO regulator with very low-dropout

voltage (600mV over the full load) and low ground current.

Along with a total accuracy of ±2% (over temperature, line

and load regulation) these regulators feature very fast tran-

sient recovery from input voltage surges and output load

current changes.

The MIC29310 is available in ﬁ xed 3.3V and 5V outputs

voltages; the MIC29312 has an adjustable output which can

be set by two external resistors to a voltage between 1.24V

to 15V. In addition, all versions are fully protected against

overcurrent faults, reversed input polarity, reversed lead

insertion, and overtemperature operation.

A TTL logic enable (EN) pin is available in the MIC29312 to

shutdown the regulator. When not used, the device can be set

to continuous operation by connecting EN to the input (IN).

The MIC29310/2 is available in the standard 3- and 5-pin

TO-220 and TO-263 packages with an operating junction

temperature range of 0°C to +125°C.

Features

• Low cost versions of MIC29300 family

• Fast transient response

• 3A current over full temperature range

• 600mV dropout voltage at full load

• Low ground current

• Accurate 1% guaranteed tolerance

• “Zero” current shutdown mode (MIC29312)

• Fixed voltage and adjustable versions

Applications

• Processor peripheral and I/O supplies

• PC add-in cards

• High-efﬁ ciency “green” computer systems

• High-efﬁ ciency linear power supplies

• High-efﬁ ciency switching supply post regulator

• Battery-powered equipment

MIC29310/29312

3A Fast-Response LDO Regulator

Typical Application

IN OUT

GND

VIN VOUT

MIC29310-x.x

Fixed Regulator Conﬁ guration

MIC29312

OUT

ADJ R1* VOUT

* For best performance, total series resistance

(R1 + R2) should be small enough to pass

the minimum regulator load current of 10mA.

R2*

GND

VIN IN

Off

VOUT = 1.240 R1

R2+ 1

Adjustable Regulator Conﬁ guration

For applications requiring even lower dropout

voltage, input voltage greater than 16V, or an

error ﬂ ag, see the MIC29300/29301/29302/

29303.

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

MIC29310/29312 Micrel

MIC29310/29312 2 November 2006

Pin Description

Pin Number Pin Number Pin Name Pin Function

MIC29310 MIC29312

1 EN Enable (Input): Active-high, logic-level enable/shutdown control.

1 2 IN Unregulated Input: +16V maximum supply.

TAB 3, TAB GND Ground: Ground pin and TAB are internally connected.

3 4 OUT Regulator Output

5 ADJ Ouput Voltage Adjust: 1.24V feedback from external resistive divider.

Pin Conﬁ guration

TAB

3OUT

2GND

1IN

MIC29310-x.xBT/WT

TO-220-3 (T)

TAB

5ADJ

4OUT

3GND

2IN

1EN

MIC29312-x.xBT/WT

TO-220-5 (T)

TAB

3OUT

2GND

1IN

MIC29310-x.xBU/WU

TO-263-3 (U)

TAB

5ADJ

4OUT

3GND

2IN

1EN

MIC29312-x.xBU/WU

TO-263-5 (U)

Absolute Maximum Ratings (Note 1)

Input Voltage (VIN) ..........................................–20V to +20V

Power Dissipation (PD) ............................. Internally Limited

Storage Temperature Range (TS) ............. –65°C to +150°C

Lead Temperature (soldering, 5 sec.) ........................ 260°C

ESD, Note 3

Operating Ratings (Note 2)

Input Voltage (VIN) ........................................ +2.3V to +16V

Junction Temperature (TJ) ............................ 0°C to +125°C

Package Thermal Resistance

TO-263 (θJC) ......................................................... 2°C/W

TO-220 (θJC) ......................................................... 2°C/W

TO-220 (θJA) ....................................................... 55°C/W

Ordering Information

Part Number Voltage Junction Temperature

Range Package

Standard RoHS Compliant(1)

MIC29310-3.3BT MIC29310-3.3WT 3.3V 0°C to +125°C TO-220

MIC29310-3.3BU MIC29310-3.3WU 3.3V 0°C to +125°C TO-263

MIC29310-5.0BT MIC29310-5.0WT 5.0V 0°C to +125°C TO-220

MIC29310-5.0BU MIC29310-5.0WU 5.0V 0°C to +125°C TO-263

MIC29312BT MIC29312WT Adj. 0°C to +125°C TO-220

MIC29312BU MIC29312WU Adj. 0°C to +125°C TO-263

Note:

1. RoHS compliant with “high-melting solder” exemption.

November 2006 3 MIC29310/29312

MIC29310/29312 Micrel

Electrical Characteristics(Note 11)

TJ = 25°C, bold values indicate 0°C ≤ TJ ≤ +125°C; unless noted

Parameter Condition Min Typ Max Units

Output Voltage 10mA ≤ IO ≤ IFL, (VOUT + 1V) ≤ VIN ≤ 8V, Note 4 –2 2 %

Line Regulation IO = 10mA, (VOUT + 1V) ≤ VIN ≤ 16V 0.06 0.5 %

Load Regulation VIN = VOUT + 1V, 10mA ≤ IOUT ≤ IFULL LOAD, Notes 4, 8 0.2 1 %

ΔVO / ΔT Output Voltage Temperature Coefﬁ cient, Note 8 20 100

ppm/°C

Dropout Voltage ΔVOUT = –1%, Note 5

O = 100mA 80 200 mV

O = 750mA 220 mV

O = 1.5A 330 mV

O = 3A 600 1000 mV

Ground Current IO = 750mA, VIN = VOUT + 1V 5 20 mA

O = 1.5A 15 mA

O = 3A 60 150 mA

IGNDDO Ground Pin VIN = 0.5V less than speciﬁ ed VOUT. IOUT = 10mA 2 3 mA

Current at Dropout

Current Limit VOUT = 0V, Note 6 3.0 3.8 A

Minimum Load Current 7 10 mA

en, Output Noise Voltage CL = 10µF 400 µVRMS

(10Hz to 100kHz) IL = 100mA CL = 33µF 260 µVRMS

Reference (MIC29312 only)

Reference Voltage 10mA ≤ IO ≤ IFL, VOUT + 1V ≤ VIN ≤ 8V, Note 4 1.215 1.265 V

MAX

Adjust Pin Bias Current 40 80 nA

120 nA

Reference Voltage Note 9 20

ppm/°C Temperature Coefﬁ cient

Adjust Pin Bias Current 0.1 nA/°C

Temperature Coefﬁ cient

Enable Input (MIC29312 only)

Input Logic Voltage low (off) 0.8 V

high (on) 2.4 V

Enable Pin Input Current VEN = VIN 15 30 µA

75 µA

EN = 0.8V – 2 µA

4 µA

Regulator Output Note 10 10 µA

Current in Shutdown 20 µA

Note 1. Exceeding the absolute maximum rating may damage the device.

Note 2. The device is not guaranteed to function outside its operating rating.

Note 3. Devices are ESD sensitive. Handling precautions recommended.

Note 4: Full Load current is deﬁ ned as 3A for the MIC29310/29312. For testing, VOUT is programmed to 5V.

Note 5: Dropout voltage is deﬁ ned as the input-to-output differential when the output voltage drops to 99% of its nominal value with VOUT + 1V applied

to VIN.

Note 6: For this test, VIN is the larger of 8V or VOUT + 3V.

Note 7: Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current plus the ground

pin current.

Note 8: Output voltage temperature coefﬁ cient is deﬁ ned as the worst case voltage change divided by the total temperature range.

Note 9: V

REF ≤ VOUT ≤ (VIN – 1V), 2.4V ≤ VIN ≤ 16V, 10mA < IL ≤ IFL, TJ ≤ TJ(max).

Note 10: V

EN ≤ 0.8V and VIN ≤ 8V, VOUT = 0.

Note 11: Speciﬁ cation for packaged product only.

MIC29310/29312 Micrel

MIC29310/29312 4 November 2006

Block Diagram

On/Off

Reference

Bias

Feed-

back

GND

16V

OUT

ADJ*

*EN

O.V.

ILIMIT

Thermal

Shut-

down

* MIC29312 only.MIC29310/29312

November 2006 5 MIC29310/29312

MIC29310/29312 Micrel

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0123

DROPOUT VOLTAGE (V)

OUTPUT CURRENT (A)

MIC2931x Dropout Voltage

vs. Output Current

0.2

0.4

0.6

0.8

-60 -30 0 30 60 90 120 150

DROPOUT VOLTAGE (mV)

TEMPERATURE (°C)

MIC2931x Dropout Voltage

vs. Temperature

LOAD

= 3A

0.0

1.0

2.0

3.0

4.0

5.0

0246

OUTPUT VOLTAGE (V)

INPUT VOLTAGE (V)

MIC29310-3.3

Dropout Characteristics

LOAD

= 3A

LOAD

= 10mA

Typical Characteristics

6.525V

4.525V

3.525V

+20mV

–20mV

OUTPUT VOLTAGE INPUT VOLTAGE

MIC29312 Line Transient Response

with 3A Load, 100F Output Capacitance

200s/division

OUT

= 3A

OUT

= 100F

6.525V

4.525V

3.525V

+20mV

–20mV

OUTPUT VOLTAGE INPUT VOLTAGE

MIC29312 Line Transient Response

with 3A Load, 10F Output Capacitance

200s/division

OUT

= 3A

OUT

=10F

0mA

200mA

3.525V

+20mV

–20mV

LOAD CURRENT OUTPUT VOLTAGE

MIC29312 Load Transient Response

(See Test Circuit Schematic)

1ms/division

= V

OUT

+ 1V

MIC29312

OUT

ADJ

GND

0.1µF 93.1k

49.9k

OUT

3.525V nominal

4 × 330µF

AVX

TPSE337M006R0100

tantalum

OUT

load (not shown): Intel® Power Validator

MIC29312 Load Transient Response Test Circuit

MIC29310/29312 Micrel

MIC29310/29312 6 November 2006

-60 -30 0 30 60 90 120 150

ADJUST PIN CURRENT (nA)

TEMPERATURE ( °C)

MIC29312 Adjust Pin Current

vs. Temperature

ILOAD = 10mA

0.0

1.0

2.0

3.0

4.0

5.0

6.0

-60 -30 0 30 60 90 120 150

GROUND CURRENT (mA)

TEMPERATURE (°C)

MIC2931x Ground Current

vs. Temperature

OUT

= 750mA

-60 -30 0 30 60 90 120 150

GROUND CURRENT (mA)

TEMPERATURE (°C)

MIC2931x Ground Current

vs. Temperature

OUT

= 1.5A

100

-60 -30 0 30 60 90 120 150

GROUND CURRENT (mA)

TEMPERATURE (°C)

MIC2931x Ground Current

vs. Temperature

OUT

= 3A

0123

GROUND CURRENT (mA)

OUTPUT CURRENT (A)

MIC2931x Ground Current

vs. Output Current

3.20

3.22

3.24

3.26

3.28

3.30

3.32

3.34

3.36

3.38

3.40

-60 -30 0 30 60 90 120 150

OUTPUT VOLTAGE (V)

TEMPERATURE (°C)

MIC29310-3.3 Output Voltage

vs. Temperature

3 DEVICES

-60 -30 0 30 60 90 120 150

CURRENT (A)

TEMPERATURE (°C)

MIC2931x Short Circuit

Current vs. Temperature

VOUT = 0V

-60 -30 0 30 60 90 120 150

ENABLE CURRENT (µA)

TEMPERATURE (°C)

MIC29312 Enable Current

vs. Temperaure

VEN = 5V

VEN = 2V

0.001

0.01

0.1

10x100

100x100

1x103

10x103

100x103

1x106

OUTPUT IMPEDANCE (Ω)

FREQUENCY (Hz)

MIC2931x Output Impedance

vs. Frequency

0.0

0.5

1.0

1.5

2.0

0246810

GROUND CURRENT (mA)

INPUT VOLTAGE (V)

MIC2931x Ground Current

vs. Input Voltage

OUT

= 10mA

100

150

200

0246810

GROUND CURRENT (mA)

INPUT VOLTAGE (V)

MIC2931x Ground Current

vs. Input Voltage

OUT

= 3A

-0.5

0.0

0.5

1.0

1.5

2.0

-20 -10 0 10 20

GROUND CURRENT (mA)

INPUT VOLTAGE (V)

MIC2931x Ground Current

vs. Input Voltage

RLOAD = 100Ω

VOUT = 3.3V

November 2006 7 MIC29310/29312

MIC29310/29312 Micrel

Applications Information

The MIC29310 and MIC29312 are high performance low-drop-

out voltage regulators suitable for all moderate to high-current

voltage regulator applications. Their 600mV of dropout voltage

at full load make them especially valuable in battery powered

systems and as high efﬁ ciency noise ﬁ lters in “post-regulator”

applications. Unlike older NPN-pass transistor designs, where

the minimum dropout voltage is limited by the base-emitter

voltage drop and collector-emitter saturation voltage, dropout

performance of the PNP output of these devices is limited

merely by the low VCE saturation voltage.

A trade-off for the low dropout voltage is a varying base

drive requirement. But Micrel’s Super ßeta PNP™ process

reduces this drive requirement to merely 2% to 5% of the

load current.

MIC29310/312 regulators are fully protected from damage

due to fault conditions. Current limiting is provided. This

limiting is linear; output current under overload conditions

is constant. Thermal shutdown disables the device when

the die temperature exceeds the maximum safe operating

temperature. Transient protection allows device (and load)

survival even when the input voltage spike above and below

nominal. The output structure of these regulators allows volt-

ages in excess of the desired output voltage to be applied

without reverse current ﬂ ow. The MIC29312 version offers a

logic level ON/OFF control: when disabled, the devices draw

nearly zero current.

An additional feature of this regulator family is a common

pinout: a design’s current requirement may change up or down

yet use the same board layout, as all of Micrel’s high-current

Super ßeta PNP™ regulators have identical pinouts.

IN OUT

GND

OUT

Figure 3. The MIC29310 regulator requires only two

capacitors for operation.

Thermal Design

Linear regulators are simple to use. The most complicated

design parameters to consider are thermal characteristics.

Thermal design requires the following application-speciﬁ c

parameters:

• Maximum ambient temperature, TA

• Output Current, IOUT

• Output Voltage, VOUT

• Input Voltage, VIN

First, we calculate the power dissipation of the regulator

from these numbers and the device parameters from this

datasheet.

PD = IOUT × (1.02VIN – VOUT)

Where the ground current is approximated by 2% of IOUT.

Then the heat sink thermal resistance is determined with

this formula:

J MAX – TA

θSA = —————— – (θJC + θCS)

Where TJ MAX ≤ 125°C and θCS is between 0 and 2°C/W.

The heat sink may be signiﬁ cantly reduced in applications

where the minimum input voltage is known and is large com-

pared 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 Micrel

Super ßeta PNP regulators allow very signiﬁ cant reductions

in regulator power dissipation and the associated heat sink

without compromising performance. When this technique is

employed, a capacitor of at least 0.1µF is needed directly

between the input and regulator ground.

Please refer to Application Note 9 for further details and ex-

amples on thermal design and heat sink speciﬁ cation.

Capacitor Requirements

For stability and minimum output noise, a capacitor on the

regulator output is necessary. The value of this capacitor

is dependent upon the output current; lower currents allow

smaller capacitors. MIC29310/2 regulators are stable with a

minimum capacitor value of 10µF at full load.

This capacitor need not be an expensive low ESR type:

aluminum electrolytics are adequate. In fact, extremely low

ESR capacitors may contribute to instability. Tantalum capaci-

tors are recommended for systems where fast load transient

response is important.

Where the regulator is powered from a source with a high

AC impedance, a 0.1µF capacitor connected between Input

and GND is recommended. This capacitor should have good

characteristics to above 250kHz.

Transient Response and 5V to 3.3V Conversion

The MIC29310/2 have excellent response to variations in

input voltage and load current. By virtue of their low dropout

voltage, these devices do not saturate into dropout as readily

as similar NPN-based designs. A 3.3V output Micrel LDO will

maintain full speed and performance with an input supply as

low as 4.2V, and will still provide some regulation with sup-

plies down to 3.8V, unlike NPN devices that require 5.1V

or more for good performance and become nothing more

than a resistor under 4.6V of input. Micrel’s PNP regulators

provide superior performance in “5V to 3.3V” conversion

applications than NPN regulators, especially when all toler-

ances are considered.

Minimum Load Current

The MIC29310/2 regulators are speciﬁ ed between ﬁ nite loads.

If the output current is too small, leakage currents dominate

MIC29310/29312 Micrel

MIC29310/29312 8 November 2006

and the output voltage rises. A 10mA minimum load current

is necessary for proper regulation.

Adjustable Regulator Design

Figure 4. Adjustable Regulator with Resistors

The adjustable regulator version, MIC29312, allows program-

ming the output voltage anywhere between 1.25V and the

15V maximum operating rating of the family. Two resistors

are used. Resistors can be quite large, up to 1MΩ, because

of the very high input impedance and low bias current of the

sense comparator. The resistor values are calculated by:

OUT

R1 = R2 × ( –—— – 1 )

1.240

Where VO is the desired output voltage. Figure 4 shows

component deﬁ nition. Applications with widely varying load

currents may scale the resistors to draw the minimum load

current required for proper operation (see the table below).

Enable Input

The MIC29312 version features an enable (EN) input that

allows ON/OFF control of the device. Special design al-

lows “zero” current drain when the device is disabled—only

microamperes of leakage current ﬂ ows. The EN input has

TTL/CMOS compatible thresholds for simple interfacing with

logic, or may be directly tied to VIN. Enabling the regulator

requires approximately 20µA of current into the EN pin.

Voltage Standard (Ω) Min. Load (Ω)

R1 R2 R1 R2

2.85 100k 76.8k 162 124

2.9 100k 75.0k 165 124

3.0 100k 69.8k 174 124

3.1 100k 66.5k 187 124

3.15 100k 64.9k 191 124

3.3 100k 60.4k 205 124

3.45 100k 56.2k 221 124

3.6 100k 52.3k 237 124

3.8 100k 48.7k 255 124

4.0 100k 45.3k 274 124

4.1 100k 43.2k 287 124

Resistor Value Table for the MIC29312 Adjustable Regulator

Note: This regulator has a minimum load requirement. “Standard” values assume the load meets this requirement. “Minimum

Load” values are calculated to draw 10mA and allow regulation with an open load (the minimum current drawn from the load

may be zero).

November 2006 9 MIC29310/29312

MIC29310/29312 Micrel

Package Information

3-Pin TO-220 (T)

3-Pin TO-263 (U)

MIC29310/29312 Micrel

MIC29310/29312 10 November 2006

5-Pin TO-220 (T)

5-Pin TO-263 (U)

November 2006 11 MIC29310/29312

MIC29310/29312 Micrel

MIC29310/29312 12 November 2006

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 speciﬁ cations at any time without notiﬁ cation 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 signiﬁ cant injury to the user. A Purchaser’s

use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser’s own risk and Purchaser agrees to fully indemnify

Micrel for any damages resulting from such use or sale.