MIC5256-2.8BM5_技术文档

MIC5256

Micrel

MIC5256

150mA µCap LDO with Error Flag

Final Information

General Description

Features

The MIC5256 is an efficient, precise CMOS voltage regula-

tor. It offers better than 1% initial accuracy, extremely low-

dropout voltage (typically 135mV at 150mA) and low ground

current (typically 90µA) over load. The MIC5256 features an

error flag that indicates an output fault condition such as

overcurrent, thermal shutdown and dropout.

• Input voltage range: 2.7V to 6.0V

• Thin SOT package: 1mm height

• Error flag indicates fault condition

• Stable with ceramic output capacitor

• Ultralow dropout: 135mV @ 150mA

• High output accuracy:

1.0% initial accuracy

2.0% over temperature

• Low quiescent current: 90µA

• Tight load and line regulation

• Thermal shutdown and current limit protection

• “Zero” off-mode current

Designed specifically for handheld and battery-powered de-

vices, the MIC5256 provides a TTL-logic-compatible enable

pin.Whendisabled,powerconsumptiondropsnearlytozero.

The MIC5256 also works with low-ESR ceramic capacitors,

reducing the amount of board space necessary for power

applications, critical in hand-held wireless devices.

• TTL logic-controlled enable input

Key features include current limit, thermal shutdown, faster

transient response, and an active clamp to speed up device

turnoff. AvailableintheIttyBitty™SOT-23-5packageandthe

new Thin SOT-23-5, which offers the same footprint as the

standardIttyBitty™SOT-23-5,butonly1mmtall.TheMIC5256

offers a range of output voltages.

Applications

• Cellular phones and pagers

• Cellular accesories

• Battery-powered equipment

• Laptop, notebook, and palmtop computers

• Consumer/personal electronics

Ordering Information

Part Number

Marking Voltage

Junction Temp. Range

–40°C to +125°C

Package

MIC5256-2.6BM5

MIC5256-2.7BM5

MIC5256-2.8BM5

MIC5256-2.85BM5

MIC5256-3.0BM5

MIC5256-3.3BM5

MIC5256-2.85BD5

LX26

LX27

LX28

LX2J

LX30

LX33

NX2J

2.6V

2.7V

2.8V

2.85V

3.0V

3.3V

2.85V

SOT-23-5

TSOT-23-5

Other voltages available. Contact Micrel for details.

Typical Application

MIC5256-x.xBM5

V_IN

EN

V_OUT

C_OUT= 1.0µF

1

5

C_IN= 1.0µF

Ceramic

2

3

Ceramic

4

Enable

Shutdown

FLG

EN (pin 3) may be

connected directly

to IN (pin 1).

Low-Noise Regulator Application

IttyBitty is a trademark of Micrel, Inc.

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

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Micrel

Pin Configuration

EN GND IN

3

2

1

3

2

1

LXxx

NWxx

4

5

4

5

FLG

BYP

OUT

MIC5256-x.xBM5

(SOT-23-5)

MIC5256-x.xBD5

(TSOT-23-5)

Pin Description

Pin Number

Pin Name

IN

Pin Function

Supply Input.

Ground.

1

2

3

GND

EN

Enable/Shutdown (Input): CMOS compatible input. Logic high = enable;

logic low = shutdown. Do not leave open.

4

5

FLG

OUT

Error Flag (Output): Open-drain output. Active low indicates an output

undervoltage condition.

Regulator Output.

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Absolute Maximum Ratings (Note 1)

Operating Ratings (Note 2)

Supply Input Voltage (V ) .................................. 0V to +7V

Input Voltage (V ) ......................................... +2.7V to +6V

IN

Enable Input Voltage (V ) .................................. 0V to V

Enable Input Voltage (V ) ................................. 0V to +7V

EN

IN

EN

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

J

Power Dissipation (P ) ............... Internally Limited, Note 3

D

Thermal Resistance

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

J

SOT-23 (θ ) .....................................................235°C/W

JA

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

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

ESD, Note 4.................................................................. 2kV

Electrical Characteristics

V_IN= V_OUT+ 1V, V_EN= V_{IN; OUT}= 100µA; T_J= 25°C, bold values indicate –40°C ≤ T_J≤ +125°C; unless noted.

I

Symbol

Parameter

Conditions

Min Typical Max

Units

V_O

Output Voltage Accuracy

I_OUT= 100µA

–1

–2

+1

+2

%

∆V_LNR

Line Regulation

V_IN= V_OUT+ 1V to 6V

I_OUT= 0.1mA to 150mA, Note 5

I_OUT= 100µA

0.02

1.5

0.1

90

0.05

2.5

%/V

%

∆V_LDR

Load Regulation

V_IN– V_OUT

Dropout Voltage, Note 6

5.0

mV

I_OUT= 100mA

150

I_OUT= 150mA

135

200

250

mV

I_Q

Quiescent Current

V

_EN≤ 0.4V (shutdown)

0.2

90

1

µA

I_GND

Ground Pin Current, Note 7

I_OUT= 0mA

150

I_OUT= 150mA

117

60

µA

PSRR

Power Supply Rejection

f = 10Hz, V_IN= V_OUT+ 1V; C_OUT= 1µF

f = 100Hz, V_IN= V_OUT+ 0.5V; C_OUT= 1µF

f = 10kHz, V_IN= V_OUT+ 0.5V

V_OUT= 0V

dB

60

dB

45

dB

I_LIM

Current Limit

160

425

tbd

mA

e_n

Output Voltage Noise

µV(rms)

Enable Input

V_IL

V_IH

I_EN

Enable Input Logic-Low Voltage

Enable Input Logic-High Voltage

Enable Input Current

V_IN= 2.7V to 5.5V, regulator shutdown

V_IN= 2.7V to 5.5V, regulator enabled

0.4

V

1.6

V

_IL≤ 0.4V, regulator shutdown

_IH≥ 1.6V, regulator enabled

0.01

500

µA

Ω

V

Shutdown Resistance Discharge

Error Flag

V_FLG

Low Threshold

High Threshold

% of V_OUT(Flag ON)

% of V_OUT(Flag OFF)

90

%

96

V_OL

I_FL

Output Logic-Low Voltage

Flag Leakage Current

I_L= 100µA, fault condition

0.02

0.01

0.1

V

flag off, V_FLG= 6V

µA

Thermal Protection

Thermal Shutdown Temperature

Thermal Shutdown Hysteresis

150

10

°C

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. The maximum allowable power dissipation of any T (ambient temperature) is P

= T

–T /θ . Exceeding the maximum allowable

J(max) A JA

A

D(max)

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power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. The θ of the MIC5255-x.xBM5 (all

JA

versions) is 235°C/W on a PC board (see “Thermal Considerations” section for further details).

Note 4. Devices are ESD sensitive. Handling precautions recommended.

Note 5. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are tested for load regulation in the load

range from 0.1mA to 150mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification.

Note 6. Dropout Voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured at 1V

differential. For outputs below 2.7V, dropout voltage is the input-to-output voltage differential with the minimum input voltage 2.7V. Minimum

input operating voltage is 2.7V.

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

pin current.

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Typical Characteristics

Power Supply Rejection Ratio

PSRR vs. Voltage Drop

70

60

50

40

30

20

10

0

70

I_LOAD= 100µA

60

50

60

50

40

30

20

10

0

100µA*

50mA*

40

I_LOAD= 150mA

50mA*

30

100mA*

150mA*

20

*I_LOAD

10

C_OUT= 1.0µF Ceramic

C_OUT= 1µF

C_OUT= 4.7µF Ceramic

0

200 400 600 800 1000

VOLTAGE DROP (mV)

FREQUENCY (Hz)

Ground Pin Current

130

115

113

111

109

107

105

103

101

99

125

120

115

110

105

100

95

125

120

115

110

105

V_IN= V_OUT+ 1V

97

I_LOAD= 100µA

I_LOAD= 150mA

100

95

0.1

1

10

100

1000

-40 -20

0

20 40 60 80 100120140

-40 -20

0

20 40 60 80 100120140

OUTPUT CURRENT (mA)

TEMPERATURE (°C)

Ground Pin Current

Dropout Characteristics

140

120

100

80

3.5

3

I_LOAD= 100µA

120

100

80

60

40

20

0

2.5

2

I_LOAD= 150mA

60

1.5

1

40

20

0.5

0

I_LOAD= 100µA

I_LOAD= 150mA

0

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

INPUT VOLTAGE (V)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

INPUT VOLTAGE (V)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

INPUT VOLTAGE (V)

Dropout Voltage

0.14

180

T = –40C

160

140

120

100

80

160

140

120

100

80

0.12

0.1

0.08

0.06

0.04

0.02

0

T = 25C

T = 125C

60

40

20

I_LOAD= 100µA

I_LOAD= 150mA

0

-40 -20

0

20 40 60 80 100120140

TEMPERATURE (°C)

-40 -20

0

20 40 60 80 100120140

TEMPERATURE (°C)

0

20 40 60 80 100 120 140 160

OUTPUT CURRENT (mA)

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Output Voltage vs.

Temperature

Short Circuit Current

600

500

490

480

470

460

450

440

430

420

410

400

3.05

3.04

3.03

3.02

3.01

3.00

2.99

2.98

2.97

2.96

2.95

V_IN= V_OUT+ 1V

500

400

300

200

100

0

I_LOAD= 100µA

3

3.5

4

4.5

5

5.5

6

-40 -20

0

20 40 60 80 100120140

-40 -20

0

20 40 60 80 100120140

INPUT VOLTAGE (V)

TEMPERATURE (°C)

Enable Threshold

vs. Temperature

Error Flag Pull-Up Resistor

1.3

4.5

4

Power Good

1.25

1.2

3.5

3

1.15

1.1

2.5

2

1.05

1

V_IN= 4V

1.5

1

0.95

0.9

0.5

0

0.85

0.8

I_LOAD= 100µA

20 40 60 80 100120140

Power Fail

-40 -20

0

0.1

1

10

100 1000 10000

TEMPERATURE (°C)

RESISTANCE (kΩ)

Test Circuits

MIC5256

1.0µF*

Ceramic

1.0µF*

Ceramic

47k

ON

OFF

0V

Error Flag Output

0.01µF

* C_IN= C_OUT= 1µF

Figure 1. Test Circuit

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Functional Characteristics

Load Transient Response

Line Transient Response

C_IN= 1µF Ceramic

C_OUT= 1µF Ceramic

I_OUT= 100µA

C_IN= 1µF Ceramic

C_OUT= 1µF Ceramic

V_IN= 4V

150mA

100µA

TIME (4µs/div)

TIME (400µs/div)

Enable Pin Delay

Shutdown Delay

C_IN= 1µF Ceramic

C_OUT= 1µF Ceramic

I_L= 100µA

C_IN= 1µF Ceramic

C_OUT= 1µF Ceramic

I_OUT= 100µA

TIME (10µs/div)

TIME (400µs/div)

Error Flag Start-up*

Error Flag Shutdown*

TIME (400µs/div)

* See Test Circuit Figure 1

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Block Diagram

IN

EN

Startup/

Shutdown

Control

Reference

Voltage

Quickstart

Thermal

Sensor

FAULT

Error

Amplifier

Current

Amplifier

OUT

Under-

voltage

Lockout

ACTIVE SHUTDOWN

Out of

Regulation

Detection

FLG

Overcurrent

Dropout

Detection

GND

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the input without using a pull-down capacitor, then there can

be a glitch on the error flag upon start up of the device. This

is due to the response time of the error flag circuit as the

device starts up. When the device comes out of the “zero” off

mode current state, all the various nodes of the circuit power

up before the device begins supplying full current to the

output capacitor. The error flag drives low immediately and

thenreleasesafterafewmicroseconds. Theintelligentcircuit

thattriggersanerrordetectstheoutputgoingintocurrentlimit

ANDtheoutputbeinglowwhilechargingtheoutputcapacitor.

The error output then pulls low for the duration of the turn-on

time. Acapacitorfromtheerrorflagtogroundwillfilteroutthis

glitch. The glitch does not occur if the error flag pulled up to

the output.

Applications Information

Enable/Shutdown

The MIC5256 comes with an active-high enable pin that

allowstheregulatortobedisabled.Forcingtheenablepinlow

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. This part is CMOS and the enable pin cannot

be left floating; a floating enable pin may cause an indetermi-

nate state on the output.

Input Capacitor

The MIC5256 is a high performance, high bandwidth device.

Therefore, it requires a well-bypassed input supply for opti-

mal performance. A 1µF capacitor is required from the input

to ground to provide stability. Low ESR ceramic capacitors

provide optimal performance at a minimum of space. Addi-

tional high-frequency capacitors, such as small valued NPO

dielectric type capacitors, help filter out high frequency noise

and are good practice in any RF based circuit.

Active Shutdown

The MIC5256 also features an active shutdown clamp, which

is an N-channel MOSFET that turns on when the device is

disabled. This allows the output capacitor and load to dis-

charge, de-energizing the load.

No Load Stability

Output capacitor

TheMIC5256willremainstableandinregulationwithnoload

unlike many other voltage regulators. This is especially

important in CMOS RAM keep-alive applications.

The MIC5256 requires an output capacitor for stability. The

design requires 1µF 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 300mΩ. The output capacitor can be increased, but

performance has been optimized for a 1µF ceramic output

capacitor and does not improve significantly with larger

capacitance.

Thermal Considerations

The MIC5256 is designed to provide 150mA of continuous

current in a very small package. Maximum power dissipation

canbecalculatedbasedontheoutputcurrentandthevoltage

drop across the part. To determine the maximum power

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

malresistanceofthedeviceandthefollowingbasicequation:

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

ceramiccapacitors.Z5UandY5Vdielectriccapacitorschange

value by as much as 50% and 60% respectively over their

operatingtemperatureranges. Touseaceramicchipcapaci-

torwithY5Vdielectric, thevaluemustbemuchhigherthanan

X7R ceramic capacitor to ensure the same minimum capaci-

tance over the equivalent operating temperature range.

T

− T

A

J(max)

P

=

D(max)

θ

JA

T

is the maximum junction temperature of the die,

125°C, and T is the ambient operating temperature. θ is

layout dependent; Table 1 shows examples of junction-to-

ambient thermal resistance for the MIC5256.

J(max)

A

JA

Package

θ_JARecommended θ_JA1" Square

Minimum Footprint

θ_JC

Copper Clad

Error Flag

SOT-23-5

(M5 or D5)

235°C/W

185°C/W

145°C/W

The error flag output is an active-low, open-drain output that

drives low when a fault condition AND an undervoltage

detection occurs. Internal circuitry intelligently monitors

overcurrent, overtemperature and dropout conditions and

ORs these outputs together to indicate some fault condition.

The output of that OR gate is ANDed with an output voltage

monitor that detects an undervoltage condition. That output

drives the open-drain transistor to indicate a fault. This

prevents chattering or inadvertent triggering of the error flag.

The error flag must be pulled-up using a resistor from the flag

pin to either the input or the output.

Table 1. SOT-23-5 Thermal Resistance

The actual power dissipation of the regulator circuit can be

determined using the equation:

P = (V – V

) I

+ V I

IN GND

D

IN

OUT OUT

Substituting P

for P and solving for the operating

D(max)

D

conditions that are critical to the application will give the

maximum operating conditions for the regulator circuit. For

example, when operating the MIC5256-3.0BM5 at 50°C with

a minimum footprint layout, the maximum input voltage for a

set output current can be determined as follows:

The error flag circuit was designed essentially to work with a

capacitor to ground to act as a power-on reset generator,

signaling a power-good situation once the regulated voltage

was up and/or out of a fault condition. This capacitor delays

the error signal from pulling high, allowing the down stream

circuits time to stablilize. When the error flag is pulled-up to

125°C − 50°C

P

=

D(max)

235°C/W

P

= 315mW

D(max)

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MIC5256

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The junction-to-ambient thermal resistance for the minimum

footprint is 235°C/W, from Table 1. The maximum power

dissipationmustnotbeexceededforproperoperation. Using

the output voltage of 3.0V and an output current of 150mA,

the maximum input voltage can be determined. Because this

device is CMOS and the ground current is typically 100µA

over the load range, the power dissipation contributed by the

groundcurrentis<1%andcanbeignoredforthiscalculation.

Fixed Regulator Applications

47kΩ

MIC5256-x.xBM5

V_IN

V_OUT

1

2

3

5

C_IN

= 1.0µF

C_OUT

= 1.0µF

Ceramic

4

315mW = (V – 3.0V) 150mA

IN

Figure 1. Low-Noise Fixed Voltage Application

315mW = V ·150mA – 450mW

IN

Figure 1 shows a standard low-noise configuration with a

47kΩ pull-up resistor from the error flag to the input voltage

and a pull-down capacitor to ground for the purpose of fault

indication. EN (Pin 3) is connected to IN (Pin 1) for an

810mW = V ·150mA

IN

V

= 5.4V

IN(max)

Therefore, a 3.0V application at 150mA of output current can

accept a maximum input voltage of 5.4V in a SOT-23-5

package. For a full discussion of heat sinking and thermal

effectsonvoltageregulators, refertotheRegulatorThermals

sectionofMicrel’sDesigningwithLow-DropoutVoltageRegu-

lators handbook.

application where enable/shutdown is not required. C

=

OUT

1.0µF minimum.

MIC5256

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MIC5256

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Package Information

1.90 (0.075) REF

0.95 (0.037) REF

1.75 (0.069) 3.00 (0.118)

1.50 (0.059) 2.60 (0.102)

DIMENSIONS:

MM (INCH)

1.30 (0.051)

0.90 (0.035)

3.02 (0.119)

2.80 (0.110)

0.20 (0.008)

0.09 (0.004)

10°

0°

0.15 (0.006)

0.00 (0.000)

0.50 (0.020)

0.35 (0.014)

0.60 (0.024)

0.10 (0.004)

SOT-23-5 (M5)

1.90BSC

2.90BSC

1.90BSC

0.30

0.45

DIMENSIONS:

Millimeter

0.90

0.80

1.00

0.90

1.60BSC

0.20

0.12

0.30

0.50

0.10

0.01

1.90BSC

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

This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or

other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel, Inc.

June 2003

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MIC5256


型号：	MIC5256-2.8BM5
厂家：	MICREL SEMICONDUCTOR
描述：	150mA UCap LDO with Error Flag 150毫安UCAP LDO具有错误标志调节器光电二极管输出元件
文件：	总11页 (文件大小：117K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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