MIC5238-1.2BM5 - Micrel, Inc.

April 2003 1 MIC5238

MIC5238 Micrel

MIC5238

Ultra-Low Quiescent Current, 150mA

Cap LDO Regulator

Final

General Description

The MIC5238 is an ultra-low voltage output, 150mA LDO

regulator. Designed to operate in a single supply or dual

supply mode, the MIC5238 consumes only 23µA of bias

current, improving efficiency. When operating in the dual

supply mode, the efficiency greatly improves as the higher

voltage supply is only required to supply the 23µA bias

current while the output and base drive comes off of the much

lower input supply voltage.

As a µCap regulator, the MIC5238 operates with a 2.2µF

ceramic capacitor on the output, offering a smaller overall

solution. It also incorporates a logic-level enable pin that

allows the MIC5238 to be put into a zero off-current mode

when disabled.

The MIC5238 is fully protected with current limit and thermal

shutdown. It is offered in the IttyBitty™ SOT-23-5 package

with an operating junction temperature range of

–40°C to +125°C.

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com

IttyBitty is a trademark of Micrel, Inc.

Features

•Ultra-low input voltage range: 1.5V to 6V

•Ultra-low output voltage: 0.9V minimum output voltage

•Low dropout voltage: 310mV at 150mA

•High output accuracy: ±2.0% over temperature

•µCap: stable with ceramic or tantalum capacitors

•Excellent line and load regulation specifications

•Zero shutdown current

•Reverse leakage protection

•Thermal shutdown and current limit protection

•IttyBitty™ SOT-23-5 package

Applications

•PDAs and pocket PCs

•Cellular phones

•Battery powered systems

•Low power microprocessor power supplies

Typical Application

COUT=2.2µF

ceramic

CIN

VBIAS=2.5V

MIC5238-1.0BM5

VIN=1.5V 1.0V

CBIAS

OFF

Ultra-Low Voltage Application

Ordering Information

Part Number Marking Voltage* Junction Temp. Range Package*

MIC5238-0.9BM5 L409 0.9V –40°C to +125°C SOT-23-5

MIC5238-1.0BM5 L410 1.0V –40°C to +125°C SOT-23-5

MIC5238-1.1BM5 L411 1.1V –40°C to +125°C SOT-23-5

MIC5238-1.2BM5 L412 1.2V –40°C to +125°C SOT-23-5

MIC5238-1.3BM5 L413 1.3V –40°C to +125°C SOT-23-5

MIC5238-1.1BD5 N411 1.1V –40°C to +125°C TSOT-23-5

MIC5238-1.3BD5 N413 1.3V –40°C to +125°C TSOT-23-5

* For other voltages and package option contact the factory.

MIC5238 Micrel

MIC5238 2 April 2003

Pin Configuration

OUT

BIAS

L4xx

GND

SOT-23-5 (M5)

Pin Description

SOT-23-5 Pin Name Pin Function

1 IN Supply Input

2 GND Ground

3 EN Enable (Input): Logic low = shutdown; logic high = enable. Do no leave

open.

4 BIAS Bias Supply Input

5 OUT Regulator Output

OUT

BIAS

N4xx

GND

TSOT-23-5 (D5)

April 2003 3 MIC5238

MIC5238 Micrel

Electrical Characteristics (Note 4)

TA = 25°C with VIN = VOUT + 1V; VBIAS = 3.3V; IOUT = 100µA; VEN = 2V, Bold values indicate –40°C<T

J< +125°C; unless otherwise specified.

Parameter Condition Min. Typ. Max. Units

Output Voltage Accuracy Variation from nominal VOUT –1.5 +1.5 %

–2+2%

Line Regulation VBIAS = 2.3V to 6V, Note 5 0.25 0.5 %

Input Line Regulation VIN = (VOUT + 1V) to 6V 0.04 %

Load Regulation Load = 100µA to 150mA 0.7 1 %

Dropout Voltage IOUT = 100µA50mV

IOUT = 50mA 230 300 mV

400 mV

IOUT = 100mA 270 mV

IOUT = 150mA 310 450 mV

500 mV

Bias Current, Note 6 IOUT = 100µA23µA

Input Current, Pin 1 IOUT = 100µA720 µA

IOUT = 50mA, Note 7 0.35 mA

IOUT = 100mA 1 mA

IOUT = 150mA 2 2.5 mA

Ground Current in Shutdown VEN ≤ 0.2V; VIN = 6V; VBIAS = 6V 1.5 5 µA

VEN = 0V; VIN = 6V; VBIAS = 6V 0.5 µA

Short Circuit Current VOUT = 0V 350 500 mA

Reverse Leakage VIN = 0V; VEN = 0V; VOUT = nom VOUT 5µA

Enable Input

Input Low Voltage Regulator OFF 0.2 V

Input High Voltage Regulator ON 2.0 V

Enable Input Current VEN = 0.2V; Regulator OFF –1.0 0.01 1.0 µA

VEN = 2.0V; Regulator ON 0.1 1.0 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. Human body model, 1.5k in series with 100pF.

Note 4. Specification for packaged product only.

Note 5. Line regulation measures a change in output voltage due to a change in the bias voltage.

Note 6. Current measured from bias input to ground.

Note 7. Current differential between output current and main input current.

Absolute Maximum Ratings (Note 1)

Input Supply Voltage ........................................ –0.3V to 7V

Bias Supply Voltage ......................................... –0.3V to 7V

Enable Input Voltage........................................ –0.3V to 7V

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

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

Storage Temperature ...............................–65°C to +150°C

ESD Rating, >1.5µA HBM, Note 3

Operating Ratings (Note 2)

Input Supply Voltage .......................................... 1.5V to 6V

BIAS Supply Voltage.......................................... 2.3V to 6V

Enable Input Voltage............................................. 0V to 6V

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

Package Thermal Resistance

SOT-23-5 (θJA)..................................................235°C/W

MIC5238 Micrel

MIC5238 4 April 2003

Typical Characteristics

0.4

0.5

0.6

0.7

0.8

0.9

1.1

1.2

1.2 1.7 2.2 2.7 3.2 3.7 4.2 4.7 5.2

OUTPUT VOLTAGE (V)

INPUT BIAS (V)

Output Voltage

vs. V

BIAS 100µA

150mA

0.8

0.85

0.9

0.95

1.05

1.1

1.15

1.11.21.31.41.51.61.71.81.9 2 2.1

OUTPUT VOLTAGE (V)

INPUT V

(V)

Output Voltage

vs. VIN 100µA

150mA

100

150

200

250

300

350

400

0 25 50 75 100 125 150

DROPOUT VOLTAGE (mV)

OUTPUT CURRENT (A)

Dropout Voltage

vs. Load

= V

OUT

+ 1

200

400

600

800

1000

1200

1400

1600

1800

0 25 50 75 100 125 150

GROUND CURRENT (µA)

OUTPUT CURRENT (mA)

Ground Current (VIN)

vs. Output Current

VIN =V

OUT + 1

0 25 50 75 100 125 150

GROUND CURRENT (µA)

OUTPUT CURRENT (mA)

Ground Current (VBIAS)

vs. Output Current

VIN = VOUT + 1

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 0.5 1.0 1.5 2.0

VIN GROUND CURRENT (mA)

VIN SUPPLY (V)

Ground Current (VIN)

vs. VIN Supply

1.1V

150mA

0 0.5 1 1.5 2 2.5 3

VBIAS GROUND CURRENT (µA)

INPUT VOLTAGE (V)

Ground Current (V

BIAS

)

vs. Input Voltage

LOAD

= 150mA

0 0.5 1 1.5 2

GROUND CURRENT (µA)

ENABLE (V)

Shutdown Current of

No Load

0 0.5 1 1.5 2

GROUND CURRENT (mA)

ENABLE (V)

Shutdown Current of VBIAS

No Load

0 0.5 1 1.5 2

GROUND CURRENT (mA)

ENABLE (V)

Shutdown Current

VBIAS + VIN Tied

No Load

-40 -20 0 20 40 60 80 100 120

GROUND CURRENT (µA)

TEMPERATURE (°C)

Ground Current (V

)

vs Temperature

1.1V

100µA

PSRR (dB)

TEMPERATURE (°C)

PSRR

150mA Load

OUT

= 2.2µF ceramic

= 2.1V

OUT

= 1.1V

10 100 1k 10k 100k 1M 10M

April 2003 5 MIC5238

MIC5238 Micrel

-40 -20 0 20 40 60 80 100 120

VIN GROUND CURRENT (µA)

TEMPERATURE (°C)

BIAS

Ground Current

vs. Temperature

1.1V

150mA

-40 -20 0 20 40 60 80 100 120

VIN GROUND CURRENT (µA)

TEMPERATURE (°C)

BIAS

Ground Current

vs. Temperature

1.1V

75mA

1.0975

1.0980

1.0985

1.0990

1.0995

1.1000

1.1005

1.1010

1.1015

1.1020

1.1025

-40 -20 0 20 40 60 80 100 120

OUTPUT VOLTAGE (V)

TEMPERATURE (°C)

Output Voltage

vs. Temperature

1.1V

100µA

100

150

200

250

300

350

400

450

500

-40 -20 0 20 40 60 80 100 120

LOAD CURRENT (mA)

TEMPERATURE (°C)

Short Circuit Current

vs. Temperature

-40 -20 0 20 40 60 80 100 120

VIN GROUND CURRENT (µA)

TEMPERATURE (°C)

BIAS

Ground Current

vs. Temperature

1.1V

100µA

100

150

200

250

300

350

400

450

500

-40 -20 0 20 40 60 80 100 120

DROPOUT VOLTAGE (mV)

TEMPERATURE (°C)

Dropout Voltage

vs. Temperature

Load = 150mA

0.4

0.6

0.8

1.2

1.4

1.6

1.8

2.2

2.4

-40 -20 0 20 40 60 80 100 120

VIN GROUND CURRENT (mA)

TEMPERATURE (°C)

VIN Ground Current

vs. Temperature

1.1V

150mA

0.2

0.4

0.6

0.8

1.2

1.4

1.6

1.8

-40 -20 0 20 40 60 80 100 120

VIN GROUND CURRENT (mA)

TEMPERATURE (°C)

VIN Ground Current

vs. Temperature

1.1V

75mA

MIC5238 Micrel

MIC5238 6 April 2003

Line Transient Response

TIME (200µs/div.)

OUTPUT VOLTAGE

(10mV/div.) INPUT VOLTAGE

(1V/div.)

3.1V

2.1V

1.1V Output

OUT

= 4.7µF ceramic

Load Transient Response

TIME (400µs/div.)

OUTPUT CURRENT

(50mA/div.) OUTPUT VOLTAGE

(200mV/div.)

1.1V output

COUT = 4.7µF ceramic

150mA

1mA

EN Turn-On Characteristic

TIME (40µs/div.)

OUTPUT VOLTAGE

(500mA/div.) ENABLE

(2V/div.)

Load Transient Response

TIME (400µs/div.)

OUTPUT CURRENT

(100mA/div.) OUTPUT VOLTAGE

(200mV/div.)

VIN = 4V

VOUT = 3V

COUT = 4.7µF ceramic

150mA

0mA

April 2003 7 MIC5238

MIC5238 Micrel

Functional Diagram

OUT

GND

BIAS

ENABLE

VREF

Block Diagram – Fixed Output Voltage

MIC5238 Micrel

MIC5238 8 April 2003

Applications Information

Enable/Shutdown

The MIC5238 comes with an active-high enable pin that

allows the regulator to be disabled. Forcing the enable pin low

disables the regulator and sends it into a “zero” off-mode-

current state. In this state, current consumed by the regulator

goes nearly to zero. Forcing the enable pin high enables the

output voltage.

Input Bias Capacitor

The input capacitor must be rated to sustain voltages that

may be used on the input. An input capacitor may be required

when the device is not near the source power supply or when

supplied by a battery. Small, surface mount, ceramic capaci-

tors can be used for bypassing. Larger values may be

required if the source supply has high ripple.

Output Capacitor

The MIC5238 requires an output capacitor for stability. The

design requires 2.2µF or greater on the output to maintain

stability. The design is optimized for use with low-ESR

ceramic chip capacitors. High ESR capacitors may cause

high frequency oscillation. The maximum recommended

ESR is 3Ω. The output capacitor can be increased without

limit. Larger valued capacitors help to improve transient

response.

X7R/X5R dielectric-type ceramic capacitors are recom-

mended because of their temperature performance. X7R-

type capacitors change capacitance by 15% over their oper-

ating 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 capaci-

tor with Y5V dielectric, the value must be much higher than a

X7R ceramic capacitor to ensure the same minimum capaci-

tance over the equivalent operating temperature range.

No-Load Stability

The MIC5238 will remain stable and in regulation with no load

unlike many other voltage regulators. This is especially

important in CMOS RAM keep-alive applications.

Thermal Considerations

The MIC5238 is designed to provide 150mA of continuous

current in a very small package. Maximum power dissipation

can be calculated based on the output current and the voltage

drop across the part. To determine the maximum power

dissipation of the package, use the junction-to-ambient ther-

mal resistance of the device and the following basic equation:

PTT

D(MAX) J(MAX) A

=−











TJ(MAX) is the maximum junction temperature of the die,

125°C, and TA is the ambient operating temperature. θJA is

layout dependent; Table 1 shows the junction-to-ambient

thermal resistance for the MIC5238.

Package θθ

θθ

θJA Recommended

Minimum Footprint

SOT-23-5 235°C/W

Table 1. SOT-23-5 Thermal Resistance

The actual power dissipation of the regulator circuit can be

determined using the equation:

PD = (VIN – VOUT)IOUT + VINIGND

Substituting PD(MAX) for PD and solving for the operating

conditions that are critical to the application will give the

maximum operating conditions for the regulator circuit. For

example, when operating the MIC5238-1.0BM5 at 50°C with

a minimum footprint layout, the maximum input voltage for a

set output current can be determined as follows:

P125 C 50 C

235 C/W

D(MAX)

=°− °











PD(MAX) = 319mW

The junction-to-ambient (θJA) thermal resistance for the

minimum footprint is 235°C/W, from Table 1. It is important

that the maximum power dissipation not be exceeded to

ensure proper operation. With very high input-to-output volt-

age differentials, the output current is limited by the total

power dissipation. Total power dissipation is calculated using

the following equation:

PD = (VIN – VOUT)IOUT + VIN x IGND + VBIAS x IBIAS

Since the bias supply draws only 18µA, that contribution can

be ignored for this calculation.

If we know the maximum load current, we can solve for the

maximum input voltage using the maximum power dissipa-

tion calculated for a 50°C ambient, 319mV.

PDMAX = (VIN – VOUT)IOUT + VIN x IGND

319mW = (VIN – 1V)150mA + VIN x 2.8mA

Ground pin current is estimated using the typical character-

istics of the device.

469mW = VIN (152.8mA)

VIN = 3.07V

For higher current outputs only a lower input voltage will work

for higher ambient temperatures.

Assuming a lower output current of 20mA, the maximum input

voltage can be recalculated:

319mW = (VIN – 1V)20mA + VIN x 0.2mA

339mW = VIN x 20.2mA

VIN = 16.8V

Maximum input voltage for a 20mA load current at 50°C

ambient temperature is 16.8V. Since the device has a 6V

rating, it will operate over the whole input range.

Dual Supply Mode Efficiency

By utilizing a bias supply the conversion efficiency can be

greatly enhanced. This can be realized as the higher bias

supply will only consume a few µA’s while the input supply will

require a few mA’s! This equates to higher efficiency saving

valuable power in the system. As an example, consider an

output voltage of 1V with an input supply of 2.5V at a load

April 2003 9 MIC5238

MIC5238 Micrel

current of 150mA. The input ground current under these

conditions is 2mA, while the bias current is only 20µA. If we

calculate the conversion efficiency using the single supply

approach, it is as follows:

Input power = VIN × output current + VIN × (VBIAS ground

current + VIN ground current)

Input power = 2.5V × 150mA + 2.5 × (0.0002+0.002) =

380.5mW

Output power = 1V × 0.15 = 150mW

Efficiency = 150/380.5 × 100 = 39.4%

Now, using a lower input supply of 1.5V, and powering the

bias voltage only from the 2.5V input, the efficiency is as

follows:

Input power = VIN × output current + VIN × VIN ground current

+ VBIAS x VBIAS ground current

Input power = 1.5 × 150mA + 1.5 × 0.002 + 2.5 × 0.0002 =

225mW

Output power = 1V × 150mA = 150mW

Efficiency = 150/225 × 100 = 66.6 %

Therefore, by using the dual supply MIC5238 LDO the

efficiency is nearly doubled over the single supply version.

This is a valuable asset in portable power management

applications equating to longer battery life and less heat

being generated in the application.

This in turn will allow a smaller footprint design and an

extended operating life.

MIC5238 Micrel

MIC5238 10 April 2003

Package Information

0.20 (0.008)

0.09 (0.004)

0.60 (0.024)

0.10 (0.004)

3.02 (0.119)

2.80 (0.110) 10°

0°

3.00 (0.118)

2.60 (0.102)

1.75 (0.069)

1.50 (0.059)

0.95 (0.037) REF

1.30 (0.051)

0.90 (0.035)

0.15 (0.006)

0.00 (0.000)

DIMENSIONS:

MM (INCH)

0.50 (0.020)

0.35 (0.014)

1.90 (0.075) REF

SOT-23-5 (M5)

1.90BSC

1.60BSC 1.60BSC

DIMENSIONS:

Millimeter

2.90BSC

0.10

0.01 0.20

0.12 0.30

0.50

0.30

0.45

0.90

0.80 2.9BSC 1.00

0.90

TSOT-23-5 (D5)

MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA

TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB http://www.micrel.com

The information furnished by Micrel in this datasheet 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 at Purchaser’s own risk and Purchaser agrees to fully indemnify

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