MIC35302WD TR - MICROCHIP TECHNOLOGY

MIC35302

3A, Low Voltage µCap LDO Regulator

**See Thermal Design Section

Super βeta PNP is a registered 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

October 2009 M9999-102309-A

General Description

The MIC35302 is a 3A low-dropout linear voltage regulator

that provides a low voltage, high current output with a

minimum of external components. It offers high precision,

ultra-low dropout (600mV over temperature), and low

ground current.

The MIC35302 operates from an input of 2.25V to 6.0V. It

is designed to drive digital circuits requiring low voltage at

high currents (i.e., PLDs, DSPs, micro-controllers, etc.),

providing an adjustable output voltage from 1.24V to 5.4V.

Features of the MIC35302 LDO include current limiting

and thermal protection, and reverse current and reverse

battery protection. Also logic (active-HIGH) enable pin is

included. The MIC35302 is available in a 5-pin power

D-Pak package (TO-252) with an operating temperature

range of –40°C to +125°C.

Data sheets and support documentation can be found on

Micrel’s web site at www.micrel.com.

Features

• 3A minimum guaranteed output current

• 600mV maximum dropout voltage over temperature

– Ideal for 3.0V to 2.5V conversion

– Ideal for 2.5V to 1.8V, 1.65V, or 1.5V conversion

• Stable with ceramic or tantalum capacitor

• Wide input voltage range

– VIN: 2.25V to 6.0V

• ±1.0% initial output tolerance

• Excellent line and load regulation speciﬁcations

• Logic controlled shutdown

• Thermal shutdown and current limit protection

• Reverse-leakage protection

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

• Power D-Pak package (TO-252)

Applications

• LDO linear regulator for low-voltage digital IC

• PC add-in cards

• High efficiency linear power supplies

• SMPS post regulator

• Battery charger

_________________________________________________________________________________________________________________________

Typical Application**

Adjustable Regulator Application

(*See Minimum Load Current Section)

Micrel, Inc. MIC35302

October 2009 2 M9999-102309-A

Ordering Information

Part Number Output Current Voltage Junction Temp. Range(1) Package

MIC35302WD* 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 Function

1 EN

Enable (Input): CMOS compatible input.

Logic high = enable, logic low = shutdown.

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

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

4 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

Functional Description Information.

5 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.

Micrel, Inc. MIC35302

October 2009 3 M9999-102309-A

Absolute Maximum Ratings(1)

Supply Voltage (VIN)..................................... –0.3V to +6.5V

Enable Input Voltage (VEN)........................... –0.3V to +6.5V

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

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

Storage Temperature (Ts) ...................–65°C ≤ TJ ≤ +150°C

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

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

Operating Ratings(2)

Supply voltage (VIN) ................................... +2.25V to +6.0V

Enable Input Voltage (VEN)................................ 0V to +6.0V

Junction Temperature Range .............–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)

TJ = 25°C with VIN = VEN = VOUT + 1V; IOUT = 10mA; bold values indicate –40°C < TJ < +125°C, unless otherwise noted.

Parameter Condition Min Typ Max Units

Output Voltage Line Regulation VIN = VOUT +1.0V to 6.0V 0.02 0.5 %

Output Voltage Load Regulation IOUT = 10mA to 3A 0.2 1 %

IOUT = 1.5A 250 450 mV Dropout Voltage, VIN – VOUT

Note 6 IOUT = 3A 370 600 mV

Ground Pin Current, Note 7 IOUT = 3A 20 50 mA

Ground Pin Current in Shutdown VIL ≤ 0.5V, VIN = VOUT + 1V 1.0 µA

Current Limit VOUT = 0 3.5 6 8.5 A

Start-up Time VEN = VIN, IOUT = 10mA, COUT = 47µF 35 150 µs

Enable Input

Regulator enable 2.25 V Enable Input Threshold

Regulator shutdown 0.8 V

VIL ≤ 0.8V (regulator shutdown) 4 µA Enable Pin Input Current

VIH ≥ 2.25V (regulator enabled) 1 15 75 µA

Adjust Pin

1.228 1.240 1.252 V Reference Voltage

1.215 1.265

Reference Voltage Temp. Coefficient Note 8 20 ppm/°C

Adjust Pin Bias Current 40 80

120

Adjust Pin Bias Current Temp.

Coefficient

0.1 nA/°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. 200V Machine Model

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. VDO = VIN – VOUT when VOUT decreased to 98% of its nominal output voltage with VIN = VOUT +1V. For output voltages below 1.75V, dropout voltage

speciﬁcation does not apply due to a minimum input operating voltage of 2.25V.

7. IGND is the quiescent current. IIN = IGND + IOUT.

8. Thermal regulation is deﬁned as the change in output voltage at a time t after a change in power dissipation is applied, excluding load or line

regulation effects. Speciﬁcations are for a 200mA load pulse at VIN = 6V for t = 10ms.

Micrel, Inc. MIC35302

October 2009 4 M9999-102309-A

Typical Characteristics

0.01 0.1 1 10 100 1000

PSRR (dB)

FREQUENCY (kHz)

Power Supply

Rejection Ratio

IOUT =3A

COUT =47µF

CIN =0

VIN =2.5V

VOUT =1.5V

0.01 0.1 1 10 100 1000

PSRR (dB)

FREQUENCY (kHz)

Power Supply

Rejection Ratio

IOUT =3A

COUT = 100µF

CIN =0

VIN =2.5V

VOUT =1.5V

Micrel, Inc. MIC35302

October 2009 5 M9999-102309-A

Functional Characteristics

Micrel, Inc. MIC35302

October 2009 6 M9999-102309-A

Functional Description

The MIC35302 is a high-performance low-dropout

voltage regulator suitable for moderate to high-current

regulator applications. Its 600mV dropout voltage at full

load and over-temperature makes it especially valuable

in battery-powered systems and as high-efficiency noise

ﬁlters in post-regulator applications. Unlike older NPN-

pass transistor designs, there the minimum dropout

voltage is limited by the based-to-emitter voltage drop

and collector-to-emitter saturation voltage, dropout

performance of the PNP output of these devices is

limited only by the low VCE saturation voltage.

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

drive requirement. Micrel’s Super ßeta PNP® process

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

load current.

The MIC35302 regulator is fully protected from damage

due to fault conditions. Current limiting is provided. This

limiting is linear; output current during 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

spikes above and below nominal. The output structure of

these regulators allows voltages in excess of the desired

output voltage to be applied without reverse current ﬂow.

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 – VOUT) IOUT + VIN IGND (1)

Where the ground current is approximated by using

numbers from the “Electrical Characteristics” or “Typical

Characteristics.” Then, the heat sink thermal resistance

is determined with this formula:

θSA = ((TJ(MAX) – TA)/ PD) – (θJC + θCS) (2)

Where TJ(MAX) ≤ 125°C and θCS is between 0°C and

2°C/W. The heat sink may be signiﬁcantly reduced in

applications where the minimum input voltage is known

and is 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 Micrel Super

ßeta PNP® regulators allow signiﬁcant reductions in

regulator power dissipation and the associated heat sink

without compromising performance. When this technique

is employed, a capacitor of at least 1.0µF 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 applications.

With no heat sink in the application, calculate the

junction temperature to determine the maximum power

dissipation that will be allowed before exceeding the

maximum junction temperature of the MIC35302. 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 MIC35302.

As an example, given an expected maximum ambient

temperature (TA) of 75°C with VIN = 2.25V, VOUT = 1.75V,

and IOUT = 2.5A, first calculate the expected PD using

Equation (1);

PD = (2.25V – 1.75V)2.5A + (2.25V)(0.027A) = 1.31W

Next, calcualte the junction temperature for the expected

power dissipation.

TJ=(θJA×PD)+TA=(56°C/W×1.31W)+75°C=148.4°C

Now determine the maximum power dissipation allowed

that would not exceed the IC’s maximum junction

temperature (125°C) without the use of a heat sink by

PD(MAX)=(TJ(MAX)–TA)/θJA=(125°C–75°C)/(56°C/W)=0.893W

Output Capacitor

The MIC35302 requires an output capacitor for stable

operation. As a µCap LDO, the MIC35302 can operate

with ceramic output capacitors as long as the amount of

capacitance is 47µF or greater. For values of output

capacitance lower than 47µF, the recommended ESR

range is 200mΩ to 2Ω. The minimum value of output

capacitance recommended for the MIC35302 is 10µF.

For 47µF or greater, the ESR range recommended is

less than 1Ω. Ultra-low ESR ceramic capacitors are

recommended for output capacitance of 47µF or greater

to help improve transient response and noise reduction

at high frequency. X7R/X5R dielectric-type 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 capacitor to ensure

the same minimum capacitance over the equivalent

operating temperature range.

Micrel, Inc. MIC35302

October 2009 7 M9999-102309-A

Input Capacitor

An input capacitor of 1.0µF or greater is recommended

when the device is more than 4 inches away from the

bulk and supply capacitance, or when the supply is a

battery. Small, surface-mount chip capacitors can be

used for the bypassing. The capacitor should be place

within 1” of 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.

Transient Response and 3.3V to 2.5V, 2.5V to 1.8V or

1.65V, or 2.5V to 1.5V Conversions

The MIC35302 has excellent transient response to

variations in input voltage and load current. The device

has been designed to respond quickly to load current

variations and input voltage variations. Large output

capacitors are not required to obtain this performance. A

standard 10µF tantalum capacitor, is all that is required.

Larger values help to improve performance even further.

By virtue of its low dropout voltage, this device does not

saturate into dropout as readily as similar NPN-based

designs. When converting from 3.3V to 2.5V, 2.5V to

1.8V or 1.65V, or 2.5V to 1.5V, the NPN-based

regulators are already operating in dropout, with typical

dropout requirements of 1.2V or greater. To convert

down to 2.5V without operating in dropout, NPN-based

regulators require an input voltage of 3.7V at the very

least. The MIC35302 regulator will provide excellent

performance with an input as low as 3.0V or 2.25V,

respectively. This gives the PNP-based regulators a

distinct advantage over older, NPN-based linear

regulators.

Minimum Load Current

The MIC35302 regulator is speciﬁed between ﬁnite

loads. If the output current is too small, leakage currents

dominate and the output voltage rises. A 10mA minimum

load current is necessary for proper operation.

Enable Input

The MIC35302 also features an enable input for on/off

control of the device. Its shutdown state draws “zero”

current (only microamperes of leakage). The enable

input is TTL/CMOS compatible for simple logic interface,

but can be connected to up to VIN. When enabled, it

draws approximately 15µA.

Adjustable Regulator Design

Figure 1. Adjustable Regulator with Resistors

The MIC35302 allows programming the output voltage

anywhere between 1.24V and 5.4V. Two resistors are

used. The resistor values are calculated by:

⎟

⎠

⎞

⎜

⎝

⎛−×= 1

1.240

R2R1 OUT

Where VOUT is the desired output voltage. Figure 1

shows component deﬁnition. Applications with widely

varying load currents may scale the resistors to draw the

minimum load current required for proper operation (see

Minimum Load Current section).

Micrel, Inc. MIC35302

October 2009 8 M9999-102309-A

Package Information

5-Pin TO-252-5 (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.

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.