Datasheet MIC2951-03BMM, MIC2951-03BN, MIC2951-3.3BM, MIC2951-4.8BM, MIC2951-03BM Datasheet (MICREL)

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Page 1

MIC2950/2951 Micrel

MIC2950/2951

150mA Low-Dropout Voltage Regulator

General Description

The MIC2950 and MIC2951 are “bulletproof” micropower voltage regulators with very low dropout voltage (typically 40mV at light loads and 250mV at 100mA), and very low quiescent current. Like their predecessors, the LP2950 and LP2951, the quiescent current of the MIC2950/MIC2951 increases only slightly in dropout, thus prolonging battery life. The MIC2950/MIC2951 are pin for pin compatible with the LP2950/LP2951, but offer lower dropout, lower quiescent current, reverse battery, and automotive load dump protection.

The key additional features and protection offered include higher output current (150mA), positive transient protection for up to 60V (load dump), and the ability to survive an unregulated input voltage transient of –20V below ground (reverse battery).

The plastic DIP and SOIC versions offer additional system functions such as programmable output voltage and logic controlled shutdown. The 3-pin TO-92 MIC2950 is pincompatible with the older 5V regulators.

These system functions also include an error flag output that warns of a low output voltage, which is often due to failing batteries on the input. This may also be used as a power-on reset. A logic-compatible shutdown input is also available which enables the regulator to be switched on and off. This part may also be pin-strapped for a 5 V output, or programmed from 1.24 V to 29 V with the use of two external resistors.

Features

• High accuracy 3.3, 4.85, or 5V, guaranteed 150mA output

• Extremely low quiescent current

• Low-dropout voltage

• Extremely tight load and line regulation

• Very low temperature coefficient

• Use as regulator or reference

• Needs only 1.5µF for stability

• Current and thermal limiting

• Unregulated DC input can withstand –20V reverse battery and +60V positive transients

• Error flag warns of output dropout (MIC2951)

• Logic-controlled electronic shutdown (MIC2951)

• Output programmable from 1.24V to 29V (MIC2951)

Applications

• Automotive Electronics

• Battery Powered Equipment

• Cellular Telephones

• SMPS Post-Regulator

• Voltage Reference

• Avionics

• High Efficiency Linear Power Supplies

Block Diagram

Unregulated DC Supply

SHDN

TTL/CMOS

Control Logic

Input

60mV

1.23V REF.

MIC2951-0x

INFB

Error Amp.

Error Detection

Comparator

182k

60k

OUT

SNS

TAP

ERR

GND

5V/150mA Output

330k

TTL/CMOS Compatible Error Output

1.5µF

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MIC2950/2951 Micrel

The MIC2950 is available as either an -05 or -06 version. The

-05 and -06 versions are guaranteed for junction temperatures from –40°C to +125°C; the -05 version has a tighter output and reference voltage specification range over temperature. The MIC2951 is available as an -02 or -03 version.

Ordering Information

Part Number Voltage Accuracy Temperature Range* Package

MIC2950-05BZ 5.0V 0.5% –40°C to +125°C TO-92 MIC2950-06BZ 5.0V 1.0% –40°C to +125°C TO-92 MIC2951-02BM 5.0V 0.5% –40°C to +125°C 8-pin SOIC MIC2951-03BM 5.0V 1.0% –40°C to +125°C 8-pin SOIC MIC2951-02BN 5.0V 0.5% –40°C to +125°C 8-pin plastic DIP MIC2951-03BN 5.0V 1.0% –40°C to +125°C 8-pin plastic DIP MIC2951-03BMM 5.0V 1.0% –40°C to +125°C 8-lead MM8™ MIC2951-3.3BM 3.3V 1.0% –40°C to +125°C 8-pin SOIC MIC2951-4.8BM 4.85V 1.0% –40°C to +125°C 8-pin SOIC

* junction temperature

The MIC2950 and MIC2951 have a tight initial tolerance (0.5% typical), a very low output voltage temperature coefficient which allows use as a low-power voltage reference, and extremely good load and line regulation (0.04% typical). This greatly reduces the error in the overall circuit, and is the result of careful design techniques and process control.

Pin Configuration

MIC2950-xx

321

OUT

GND

TO-92 (Z)

(Bottom View)

Pin Description

Pin # Pin # Pin Name Pin Function

MIC2950 MIC2951

3 1 OUT Regulated Output

2 SNS Sense (Input): Output-voltage sensing end of internal voltage divider for

fixed 5V operation. Not used in adjustable configuration.

3 SHDN Shutdown/Enable (Input): TTL compatible input. High = shutdown,

low or open = enable.

2 4 GND Ground

5 ERR Error Flag (Output): Active low, open-collector output (low = error,

floating = normal).

6 TAP 3.3V/4.85/5V Tap: Output of internal voltage divider when the regulator is

configured for fixed operation. Not used in adjustable configuration.

7 FB Feedback (Input): 1.235V feedback from internal voltage divider’s TAP (for

fixed operation) or external resistor network (adjustable configuration).

1 8 IN Unregulated Supply Input

MIC2951-xx

OUT SNS

SHDN

GND

1 2 3 4

TAP

ERR

DIP (N), SOIC (M), MM8™ (MM)

(Top View)

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MIC2950/2951 Micrel

Absolute Maximum Ratings (Note 1)

Input Suppy Voltage (VIN) Note 5 ................. –20V to +60V

Feedback Input Voltage (VFB) Note 6, 7...... –1.5V to +26V

Shutdown Input Voltage (V

Power Dissipation (PD) Note 4 ................Internally Limited

) Note 6 ..... –0.3V to +30V

SHDN

Operating Ratings (Note 2)

Input Supply Voltage (VIN) ........................... +2.0V to +30V

Junction Temperature (TJ) ....................................... Note 4

MIC2950-05/MIC2950-06.....................–40°C to +125°C

MIC2951-02/MIC2950-03.....................–40°C to +125°C

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

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

ESD, Note 3

Electrical Characteristics

VIN = 6V; IL = 100µA; CL = 1µF; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; Note 8; unless noted. Parameter Condition Min Typ Max Units

Output Voltage MIC295x-02/-05 (±0.5%), TJ = 25°C 4.975 5.000 5.025 V

MIC295x-03/-06 (±1%), TJ = 25°C 4.950 5.000 5.050 V MIC2951-3.3 (±1%), TJ = 25°C 3.267 3.300 3.333 V MIC2951-4.8 (±1%), TJ = 25°C 4.802 4.850 4.899 V

Output Voltage MIC295x-02/-05 (±0.5%), –25°C ≤ TJ ≤ +85°C 4.950 5.050 V

MIC295x-03/-06 (±1%), –25°C ≤ TJ ≤ +85°C 4.925 5.075 V MIC2951-3.3 (±1%), –25°C ≤ TJ ≤ +85°C 3.251 3.350 V MIC2951-4.8 (±1%), –25°C ≤ TJ ≤ +85°C 4.777 4.872 V

Output Voltage MIC295x-02/-05 (±0.5%), –40°C to +125°C 4.940 5.060 V Over Full Temperature Range

Output Voltage MIC295x-02/-05 (±0.5%), 100µA ≤ IL ≤ 150mA, TJ ≤ T Over Load Variation

Output Voltage MIC295x-02/-05 (±0.5%), Note 9 20 100 ppm/°C Temperature Coefficient

Line Regulation MIC295x-02/-05 (±0.5%), Note 10, 11 0.03 0.10 %

MIC295x-03/-06 (±1%), –40°C to +125°C 4.900 5.100 V MIC2951-3.3 (±1%), –40°C to +125°C 3.234 3.366 V MIC2951-4.8 (±1%), –40°C to +125°C 4.753 4.947 V

J(max)

MIC295x-03/-06 (±1%), 100µA ≤ IL ≤ 150mA, TJ ≤ T MIC2951-3.3 (±1%), 100µA ≤ IL ≤ 150mA, TJ ≤ T MIC2951-4.8 (±1%), 100µA ≤ IL ≤ 150mA, TJ ≤ T

MIC295x-03/-06 (±1%), Note 9 50 150 ppm/°C MIC2951-3.3 (±1%), Note 9 50 150 ppm/°C MIC2951-4.8 (±1%), Note 9 50 150 ppm/°C

MIC295x-03/-06 (±1%), Note 10, 11 0.04 0.20 %

MIC2951-3.3 (±1%), Note 10, 11 0.04 0.20 %

MIC2951-4.8 (±1%), Note 10, 11 0.04 0.20 %

J(max) J(max) J(max)

4.930 5.070 V

4.880 5.120 V

3.221 3.379 V

4.733 4.967 V

0.20 %

0.40 %

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MIC2950/2951 Micrel

Parameter Condition Min Typ Max Units

Load Regulation MIC295x-02/-05 (±0.5%), 100µA ≤ I

MIC295x-03/-06 (±1%), 100µA ≤ I

MIC2951-3.3 (±1%), 100µA ≤ I

MIC2951-4.8 (±1%), 100µA ≤ I

Dropout Voltage MIC295x-02/-03/-05/-06, I

= 100µA, Note 12 40 80 mV

MIC295x-02/-03/-05/-06, IL = 100mA, Note 12 250 300 mV MIC295x-02/-03/-05/-06, I

MIC2951-3.3 (±1%), I

= 150mA, Note 12 300 450 mV

= 100µA, Note 12 40 80 mV

MIC2951-3.3 (±1%), IL = 100mA, Note 12 250 350 mV MIC2951-3.3 (±1%), I

MIC2951-4.8 (±1%), I

= 150mA, Note 12 320 450 mV

= 100µA, Note 12 40 80 mV

MIC2951-4.8 (±1%), IL = 100mA, Note 12 250 300 mV MIC2951-4.8 (±1%), I

Ground Current MIC295x-02/-03/-05/-06, I

MIC295x-02/-03/-05/-06, I

MIC2951-3.3 (±1%), I

= 150mA, Note 12 300 450 mV

= 100µA 120 180 µA

= 100mA 1.7 2.5 mA

= 150mA 4 6 mA

= 100µA 100 180 µA

MIC2951-3.3 (±1%), IL = 100mA 1.7 2.5 mA MIC2951-3.3 (±1%), I

MIC2951-4.8 (±1%), I

= 150mA 4 6 mA

= 100µA 120 180 µA

= 100mA 1.7 2.5 mA

= 150mA 4 6 mA

Dropout Ground Current MIC295x-02/-03/-05/-06 (±0.5%), V

MIC2951-3.3 (±1%), V

MIC2951-4.8 (±1%), V

= 3.0V, IL = 100µA 150 350 µA

= 4.3V, IL = 100µA 280 350 µA

≤ 150mA, Note 10 0.04 0.10 %

0.20 %

≤ 150mA, Note 10 0.10 0.20 %

0.30 %

≤ 150mA, Note 10 0.10 0.20 %

0.30 %

140 mV

600 mV

150 mV

600 mV

140 mV

600 mV

300 µA

3.5 mA

8 mA

300 µA

10 mA

300 µA

3.5 mA

8 mA

= 4.5V, IL = 100µA 280 350 µA

400 µA

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MIC2950/2951 Micrel

Parameter Condition Min Typ Max Units

Current Limit V

Thermal Regulation Note 13 0.05 0.20 %/W Output Noise 10Hz to 100kHz, CL = 1.5µF 430 µV

Reference Voltage MIC295x-02/-05 (±0.5%) 1.220 1.235 1.250 V

Reference Voltage MIC295x-02/-05 (±0.5%), Note 14 1.190 1.270 V

Feedback Bias Current 20 40 nA

Reference Voltage MIC295x-02/-05 (±0.5%), Note 9 20 ppm/°C Temperature Coefficient

Feedback Bias Current 0.1 nA/°C Temperature Coefficient

Error Comparator (Flag) V Output Leakage Current 2.00 µA

Error Comparator (Flag) V Output Low Voltage 400 mV

Error Comparator Note 15 40 60 mV Upper Threshold Voltage 25 mV

Error Comparator Note 15 75 95 mV Lower Threshold Voltage 140 mV

Error Comparator Hysteresis Note 15 15 mV

= 0V 300 400 mA

OUT

450 mA

RMS

10Hz to 100kHz, CL = 200µF 160 µV 10Hz to 100kHz, CL = 3.3µF, 100 µV

RMS RMS

0.01µF bypass Feedback to Output

1.200 1.260 V

MIC295x-03/-06 (±1%) 1.210 1.235 1.260 V

1.200 1.270 V

MIC2951-3.3 (±1%) 1.210 1.235 1.260 V

1.200 1.270 V

MIC2951-4.8 (±1%) 1.210 1.235 1.260 V

1.200 1.270 V

MIC295x-03/-06 (±1%), Note 14 1.185 1.285 V MIC2951-3.3 (±1%), Note 14 1.185 1.285 V MIC2951-4.8 (±1%), Note 14 1.185 1.285 V

60 nA

MIC295x-03/-06 (±1%), Note 9 50 ppm/°C MIC2951-3.3 (±1%), Note 9 50 ppm/°C MIC2951-4.8 (±1%), Note 9 50 ppm/°C

= 30V 0.01 1.00 µA

= 4.5V, IOL = 200µA 150 250 mV

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MIC2950/2951 Micrel

Parameter Condition Min Typ Max Units

Shutdown Input Logic Voltage MIC295x-02/-05 (±0.5%) 1.3 V

Low 0.7 V High 2.0 V

MIC295x-03/-06 (±1%) 1.3 V

Low 0.7 V High 2.0 V

MIC2951-3.3 (±1%) 1.3 V

Low 0.7 V High 2.0 V

MIC2951-4.8 (±1%) 1.3 V

Low 0.7 V High 2.0 V

Shutdown Input Current V

SHUTDOWN

Regulator Output Current Note 7 310µA 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 are recommended. Note 4. The junction-to-ambient thermal resistance of the TO-92 package is 180°C/W with 0.4” leads and 160°C/W with 0.25” leads to a PC board.

Note 5. The maximum positive supply voltage of 60V must be of limited duration (≤100ms) and duty cycle (≤1%). The maximum continuous supply

Note 6. When used in dual-supply systems where the output terminal sees loads returned to a negative supply, the output voltage should be diode-

Note 7. V Note 8. Additional conditions for 8-pin devices are VFB = 5V, TAP and OUT connected to SNS (V Note 9. Output or reference voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. Note 10. Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating

Note 11. Line regulation for the MIC2951 is tested at 150°C for IL = 1mA. For IL = 100µA and TJ = 125°C, line regulation is guaranteed by design to

Note 12. Dropout voltage is defined as the input to output differential at which the output voltage drops 100mV below its nominal value measured at 1V

Note 13. 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

Note 14. V Note 15. Comparator thresholds are expressed in terms of a voltage differential at the FB terminal below the nominal reference voltage measured at 6V

The thermal resistance of the 8-pin DIP package is 105°C/W junction-to-ambient when soldered directly to a PC board. Junction-to-ambient thermal resistance for the SOIC (M) package is 160°C/W. Junction-to-ambient thermal resistance for the MM8™ (MM) is 250°C/W.

voltage is 30V.

clamped to ground.

≥ 2V, VIN ≤ 30 V, V

SHDN

effects are covered in the specification for thermal regulation.

0.2%. See Typical Performance Characteristics for line regulation versus temperature and load current.

differential. At very low values of programmed output voltage, the minimum input supply voltage of 2V (2.3V over temperature) must be taken into account.

regulation effects. Specifications are for a 50mA load pulse at VIN = 30V (1.25W pulse) for t = 10ms.

≤ V

REF

input. To express these thresholds in terms of output voltage change, multiply by the error amplifier gain = V (R1 + R2)/R2. For example, at a programmed output voltage of 5V, the error output is guaranteed to go low when the output drops by 95mV x 5V/1.235V = 384mV. Thresholds remain constant as a percent of V typically 5% below nominal, 7.5% guaranteed.

≤ (VIN – 1 V), 2.3V ≤ VIN ≤ 30V, 100µA < IL ≤ 150mA, TJ ≤ T

OUT

= 0, with the FB pin connected to TAP.

OUT

= 2.4V 30 50 µA

100 µA

= 30V 450 600 µA

750 µA

JMAX

OUT

as V

= 5V) and V

OUT

is varied, with the dropout warning occurring at

OUT

SHDN

≤ 0.8V.

OUT

REF

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MIC2950/2951 Micrel

Typical Characteristics

Ground Pin Current Dropout Characteristics Input Current

R = 50k

Ω

R = 33

Ω

0.1

QUIESCENT CURRENT

0.01

0.1 1 10 150

OUTPUT VOLTAGE (V)

1 0

012345 6

400 350 300 250 200 150 100

INPUT CURRENT (µA)

012345678910

LOAD CURRENT (mA) INPUT VOLTAGE (V) INPUT VOLTAGE (V)

Output Voltage vs. Temperature of 3

160 150 140 130 120 110 100

90 80 70 60 50 40 30

INPUT CURRENT (mA)

20 10

012345678910

R = 50

Representative UnitsInput Current

5.06

Ω

5.04

5.02

5.0

4.98

4.96

OUTPUT VOLTAGE (V)

4.94

-75 -50 -25 0 25 50 75 100 125 150

0.2%

Ground Pin Current

180 140 120 100

80 60 40 20

QUIESCENT CURRENT (µA)

012345678

R = 50kLΩ

R =

∞

I = 1 mA

I = 0

INPUT VOLTAGE (V)TEMPERATURE (°C)INPUT VOLTAGE (V)

350 300

V = 6V

250

I = 100 µA

200 150 100

QUIESCENT CURRENT (µA)

-75-50 -25 0 25 50 75 100 125 150 TEMPERATURE (°C) TEMPERATURE (°C) INPUT VOLTAGE (V)

450 400

350 300 250 200 150 100

SHORT CIRCUIT CURRENT (mA)

-75-50 -25 0 25 50 75 100 125 150 TEMPERATURE (°C) TEMPERATURE (°C) OUTPUT CURRENT (mA)

Ground Pin CurrentGround Pin CurrentGround Pin Current

V = 6V

I = 150 mA

QUIESCENT CURRENT (mA)

-75 -50 -25 0 25 50 75 100 125150

Dropout VoltageShort Circuit Current Dropout Voltage

600 500

I = 150 mA

400

QUIESCENT CURRENT (mA)

012345678

500

400

300

100

I = 100 µA

DROPOUT VOLTAGE (mV)

-75 -50 -25 0 25 50 75 100 125150

200

T = 25 °C

100

DROPOUT VOLTAGE (mV)

0.1

I = 150 mA

150

10 100

February 1999 3-55

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MIC2950/2951 Micrel

MIC2951 Minimum Operating Voltage

2.2

2.1

2.0

1.9

1.8

1.7

1.6

-75 -50 -25 0 25 50 75 100 125 150

MINIMUM OPERATING VOLTAGE (V)

TEMPERATURE (°C) FEEDBACK VOLTAGE (V)

MIC2951 Error Comparator Output

V = 5V

COMPARATOR OUTPUT (V)

-2 01234 65

OUT

HYSTERESIS

PULLUP RESISTOR TO SEPARATE 5V SUPPLY

MIC2951 Feedback Bias Current

-10

-20

BIAS CURRENT (nA)

-30

-75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (°C)

MIC2951 Comparator Sink Current

2.5 T = 125°C

2.0

1.5

1.0

0.5

SINK CURRENT (mA)

0.0

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

T = 25°C

T = -55°C

MIC2951 Feedback Pin Current

PIN 7 DRIVEN BY EXTERNAL SOURCE (REGULATOR RUN

OPEN LOOP)

-50 T = 125°C

-100

-150

-200

FEEDBACK CURRENT (µA)

-250

-2.0 -1.5 -1.0 -0.5 0 0.5 1.0

Line Transient Response

400

200

CHANGE

-50 mV

OUTPUT VOLTAGE

INPUT

VOLTAGE

0 200 400 600 800

T = 25°C

T = –55°C

TIME (µS)OUTPUT LOW VOLTAGE (V)INPUT VOLTAGE (V)

C = 4.7µF

I = 1 mA

V = 5V

OUT

125 100

75 50

CHANGE (mV)

-25

OUTPUT VOLTAGE

-50

100

LOAD

µA

CURRENT

0246810

C = 4.7 µF V = 5V

OUT

TIME (mS) TIME (mS)

I = 100 µA

I = 1 mA

0.5

0.2

0.1

0.05

0.02

OUTPUT IMPEDANCE (OHMS)

0.01 10 100 1K 10K 100K 1M

FREQUENCY (Hz) FREQUENCY (Hz)

I = 100 mA

V = 5V

OUT

C = 4.7 µF

Load Transient ResponseLoad Transient Response

80 60 40 20

-20

CHANGE (mV)

-40

OUTPUT VOLTAGE

-60

100

LOAD

µA

CURRENT

0 4 8 12 16 20

C = 15 µF

V = 5V

OUT

Ripple RejectionOutput Impedance

90 80 70 60 50

C = 1.5 µF

V = 6V

V = 5V

RIPPLE REJECTION (dB)

OUT

1346

10 10

I = 0

I = 100 µA

MIC2951 Enable Transient

7 6

5 4

OUTPUT

VOLTAGE (V)

2 1 0 2 0

-2

SHUTDOWN

-100 0 100 200 300 400 500 600 700

PIN VOLTAGE (V)

C = 1.5 µF

C = 10 µF

TIME (µS)

I = 10 mA

V = 8V

V = 5V

OUT

Ripple Rejection

90 80 70

I = 1 mA

60 50 40 30

RIPPLE REJECTION (dB)

10101010

123456

10 10

FREQUENCY (Hz)

C = 1.5 µF V = 6V V = 5V

I = 10 mA

L IN OUT

10101010

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MIC2950/2951 Micrel

)

Ripple Rejection

I = 50 µA

70 60

I = 100 mA

50 40

C = 1.5 µF

V = 6V

V = 5V

OUT

RIPPLE REJECTION (dB)

123456

10 10 10101010

FREQUENCY (Hz)

Shutdown Threshold Voltage

1.8

1.6

1.4

1.2

1.0

0.8

0.6

-75 -50-25 0 25 50 75 100125 150

SHUTDOWN THRESHOLD VOLTAGE (V)

TEMPERATURE (°C)

Output Noise MIC2951 Divider Resistance

3.5

√

3.0

2.5 C = 220 µF

2.0

C =

1.5

3.3 µF

1.0

VOLTAGE NOISE

0.01 µF BYPASS

0.5

PIN 1 TO

SPECTRAL DENSITY (µV/ Hz)

PIN 7

0.0

234 5

10 101010

I = 100 mA

C = 4.7 µF

Ω

400

300

200

100

PIN 2 TO PIN 4 RESISTANCE (k )

-75 -50-25 0 25 50 75 100125 150

FREQUENCY (Hz) TEMPERATURE (°C)

Line Regulation

30 25

20 15 10

T = 150°C

I = 100 µA

I = 1 mA

T = 125°C

I = 100 µA

-5

-10

OUTPUT VOLTAGE CHANGE (mV)

5 1015202530

MIC2951 Maximum Rated Output Current

150 140 130 120 100

80 60

T = 50°C

OUTPUT CURRENT (mA)

T = 85°C

0 5 10 15 20 25 30

INPUT VOLTAGE (V) INPUT VOLTAGE (V)

8-PIN SOIC SOLDERED TO PC BOARD

T = 125°C

MAX

V = 5V

OUT

T = 25°C

MIC2950 Maximum Rated Output

150 140 130

TO-92 PACKAGE

.25" LEADS SOLDERED

TO PC BOARD

120 100

80 60 40

OUTPUT CURRENT (mA)

T = 85°C

0 5 10 15 20 3025

INPUT VOLTAGE (V)

T = 125°C

MAX

T = 25°C

Thermal Response

5 4

Fold-Back Current Limiting

600

500

CHANGE (mV)

OUTPUT VOLTAGE

-2 1

POWER

-1

DISSIPATION (W)

01020 5030 40

1.25W

TIME (µS

400

300

200

OUTPUT CURRENT (mA)

100

012 534

OUTPUT VOLTAGE (V

February 1999 3-57

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MIC2950/2951 Micrel

Applications Information

Automotive Applications

The MIC2950/2951 are ideally suited for automotive applications for a variety of reasons. They will operate over a wide range of input voltages, have very low dropout voltages (40mV at light loads), and very low quiescent currents. These features are necessary for use in battery powered systems, such as automobiles. They are also “bulletproof” devices; with the ability to survive both reverse battery (negative transients up to 20V below ground), and load dump (positive transients up to 60V) conditions. A wide operating temperature range with low temperature coefficients is yet another reason to use these versatile regulators in automotive designs.

External Capacitors

A 1.5 µF (or greater) capacitor is required between the MIC2950/MIC2951 output and ground to prevent oscillations due to instability. Most types of tantalum or aluminum electrolytics will be adequate; film types will work, but are costly and therefore not recommended. Many aluminum electrolytics have electrolytes that freeze at about –30°C, so solid tantalums are recommended for operation below –25°C. The important parameters of the capacitor are an effective series resistance of about 5Ω or less and a resonant frequency above 500kHz. The value of this capacitor may be increased without limit.

At lower values of output current, less output capacitance is required for output stability. The capacitor can be reduced to

0.5µF for current below 10mA or 0.15µF for currents below 1 mA. Using the 8-pin versions at voltages below 5V runs the error amplifier at lower gains so that more output capacitance is needed. For the worst-case situation of a 150mA load at

1.23V output (Output shorted to Feedback) a 5µF (or greater) capacitor should be used.

The MIC2950 will remain stable and in regulation with no load in addition to the internal voltage divider, unlike many other voltage regulators. This is especially important in CMOS RAM keep-alive applications. When setting the output voltage of the MIC2951 version with external resistors, a minimum load of 1µA is recommended.

A 0.1µF capacitor should be placed from the MIC2950/ MIC2951 input to ground if there is more than 10 inches of wire between the input and the AC filter capacitor or if a battery is used as the input.

Stray capacitance to the MIC2951 Feedback terminal (pin 7) can cause instability. This may especially be a problem when using high value external resistors to set the output voltage. Adding a 100pF capacitor between Output and Feedback and increasing the output capacitor to at least 3.3µF will remedy this.

Error Detection Comparator Output

A logic low output will be produced by the comparator whenever the MIC2951 output falls out of regulation by more than approximately 5%. This figure is the comparator’s built-in

offset of about 60mV divided by the 1.235V reference voltage. (Refer to the block diagram on Page 1). This trip level remains “5% below normal” regardless of the programmed output voltage of the MIC2951. For example, the error flag trip level is typically 4.75V for a 5V output or 11.4V for a 12V output. The out of regulation condition may be due either to low input voltage, current limiting, thermal limiting, or overvoltage on input (over ≅ 40V).

Figure 1 is a timing diagram depicting the ERROR signal and the regulated output voltage as the MIC2951 input is ramped up and down. The ERROR signal becomes valid (low) at about 1.3V input. It goes high at about 5V input (the input voltage at which V

= 4.75—for 5.0V applications). Since

OUT

the MIC2951’s dropout voltage is load-dependent (see curve in Typical Performance Characteristics), the input voltage trip point (about 5V) will vary with the load current. The output voltage trip point does not vary with load.

The error comparator has an open-collector output which requires an external pull-up resistor. Depending on system requirements, this resistor may be returned to the output or some other supply voltage. In determining a value for this resistor, note that while the output is rated to sink 200µA, this sink current adds to battery drain in a low battery condition. Suggested values range from 100k to 1MΩ. The resistor is not required if this output is unused.

Programming the Output Voltage (MIC2951)

The MIC2951 may be pin-strapped for 5V (or 3.3V or 4.85V) using its internal voltage divider by tying Pin 1 (output) to Pin 2 (sense) and Pin 7 (feedback) to Pin 6 (5V Tap). Alternatively, it may be programmed for any output voltage between its

1.235V reference and its 30V maximum rating. An external pair of resistors is required, as shown in Figure 2.

The complete equation for the output voltage is V

OUT

where V

= V

x { 1 + R1/R2 } + IFB R

REF

is the nominal 1.235 reference voltage and IFB is

REF

the feedback pin bias current, nominally –20nA. The minimum recommended load current of 1 µA forces an upper limit of

1.2MΩ on the value of R2, if the regulator must work with no load (a condition often found in CMOS in standby), IFB will produce a 2% typical error in V

which may be eliminated

OUT

at room temperature by trimming R1. For better accuracy, choosing R2 = 100k reduces this error to 0.17% while increasing the resistor program current to 12 µA.

Reducing Output Noise

In some applications it may be advantageous to reduce the AC noise present at the output. One method is to reduce the regulator bandwidth by increasing the size of the output capacitor. This is the only method by which noise can be reduced on the 3 lead MIC2950 and is relatively inefficient, as increasing the capacitor from 1µF to 220µF only decreases the noise from 430µV to 160µV rms for a 100kHz bandwidth at 5V output.

3-58 February 1999

Page 11

MIC2950/2951 Micrel

Noise can be reduced fourfold by a bypass capacitor across R1, since it reduces the high frequency gain from 4 to unity. Pick:

OUTPUT

VOLTAGE

ERROR

INPUT

VOLTAGE

BYPASS

NOT

VALID

≅

4.75V

1.3V

• 200 Hz

NOT

VALID

or about 0.01 µF. When doing this, the output capacitor must be increased to 3.3 µF to maintain stability. These changes reduce the output noise from 430 µV to 100 µV rms for a 100 kHz bandwidth at 5V output. With the bypass capacitor added, noise no longer scales with output voltage so that improvements are more dramatic at higher output voltages.

ERROR OUTPUT

SHUTDOWN INPUT

100kΩ

OFF

ERROR

MIC2951

GND FB

OUT

1.23V

REF

OUT

x (1 + )

OUT

1.2

100

30V

= V

R R

3.3µF

REF

1 2

* SEE APPLICATIONS INFORMATION

Figure 1. ERROR Output Timing Figure 2. Adjustable Regulator

Typical Applications

*SLEEP INPUT

47kΩ

OFF

ERROR

ERROR OUTPUT

SHUTDOWN INPUT

*HIGH INPUT LOWERS V

5V Regulator with 2.5V Sleep Function

MIC2951

GND

TO 2.5V

OUT

C-MOS GATE

2N3906

100pF

470 kΩ

200kΩ 1% 100kΩ

1% 100kΩ

OUT

3.3µF

NOTE: PINS 2 AND 6 ARE LEFT OPEN

*SEE APPLICATIONS INFORMATION

*V ≈V

ERROR OUTPUT

ERROR

OUT

MIC2951

OFF

GND

SHUTDOWN INPUT

*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV, DEPENDING ON LOAD CURRENT.

Wide Input Voltage Range Current Limiter

870 23

870 25

February 1999 3-59

Page 12

MIC2950/2951 Micrel

SHUTDOWN INPUT

+V = 2→30V

OUT

1µF

1.23V

OFF

↓

LOAD

MIC2951

GND

Low Drift Current Source

5V BUS

OUT

≈5V

MIC2950Z

1µF

0.1µF

GND

870 27

5-Volt Current Limiter

* MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mV, DEPENDING ON LOAD CURRENT.

2.7MΩ

SENSE

MIC2951

GND

SENSE

MIC2951

GND

OUT

ERROR

27kΩ

OUT

ERROR

MEMORY

V+

1µf

V+

3.6V

3.6V NICAD

NICAD

RESET

µP

870 29

1µF

EARLY WARNING

330kΩ

MAIN

OUTPUT

Regulator with Early Warning and Auxiliary Output

• EARLY WARNING FLAG ON LOW INPUT VOLTAGE

• MAIN OUTPUT LATCHES OFF AT LOWER INPUT VOLTAGES

• BATTERY BACKUP ON AUXILIARY OUTPUT OPERATION: REG. #1’S V

ITS ERROR FLAG BECOMES ACTIVE WHEN VIN ≤ 5.7 V. WHEN VIN DROPS BELOW 5.3 V, THE ERROR FLAG OF REG. #2 BECOMES ACTIVE AND VIA Q1 LATCHES THE MAIN OUTPUT OFF. WHEN VIN AGAIN EXCEEDS 5.7 V REG. #1 IS BACK IN REGULATION AND THE EARLY WARNING SIGNAL RISES, UNLATCHING REG. #2 VIA D3.

IS PROGRAMMED ONE DIODE DROP ABOVE 5 V.

OUT

3-60 February 1999

Page 13

MIC2950/2951 Micrel

470kΩ

RESET

ERROR

MIC2951

GND

20mA

OUT

1µF

1N 4001

0.1µF

MIC2951

GND

OUT

1N457

4.7mA

360

+5V

OUTPUT*

* HIGH FOR I < 3.5mA

Latch Off When Error Flag Occurs

39kΩ

RESET

–

LEADACID BATTERY

C1-C4 LP339

39kΩ

100 kΩ

1 kΩ

10kΩ

20kΩ

ERROR

MIC2951

GND

–

MIN. VOLTAGE 4V

Open Circuit Detector for 4mA to 20mA Current Loop

SENSE

OUT

= 5V

1µF

TAP

100kΩ

<5.8V**

100kΩ

<6.0V**

100kΩ

<6.2V**

870 33

Regulator with State-of-Charge Indicator

February 1999 3-61

C1 TO C4 ARE COMPARATORS (LP339 OR EQUIVALENT) *OPTIONAL LATCH OFF WHEN DROP OUT OCCURS. ADJUST R3 FOR C2

SWITCHING WHEN V **OUTPUTS GO LOW WHEN V

IS 6.0V

DROPS BELOW DESIGNATED THRESHOLDS.

Page 14

MIC2950/2951 Micrel

6V SEALED

120kΩ

LEADACID BATTERY

SOURCE

≈ 400kΩ*

FOR 5.5V

* Sets disconnect voltage ** Sets disconnect hysteresis

For values shown, Regulator shuts down when VIN < 5.5 V and turns on again at 6.0 V. Current drain in disconnected mode is 150µA.

1.5kΩ**

LM385

–

100kΩ

1N457

MIC2951

Low-Battery Disconnect

GND

SENSE

OUT

1µF

AUX. SHUTDOWN

TEMP.

SENSOR

LM34 for 125°F Shutdown LM35 for 125°C Shutdown

Schematic Diagram

50 kΩ

10 kΩ

INPUT

Q42

Q40

OFF

LM34 OR

LM35

–

20 kΩ

50 kΩ

Q41

R30

30 kΩ

ERROR

10kΩ

5° PRE-SHUTDOWN FLAG

MIC2951

OUT

GND

EXTERNAL CIRCUIT PROTECTED FROM

OVER TEMPERATURE

(V+ GOES OFF WHEN

TEMP.> 125°)

8.2kΩ

System Overtemperature Protection Circuit

50 kΩ

R11 18 kΩ

180

kΩ

ERROR

Q15A

Q4Q3

C1 20 pF

31.4 kΩ

140

27.8 kΩ

kΩ

Q12

Q13

13 kΩ

Q37

Q38

Q39

R11

20.6

kΩ

R25

2.8 kΩ

Q20

R12

110

kΩ

Q34

R10

150

kΩ

Q11

Q36

R26 60 kΩ

Q18

Q16

R13 100

kΩ

GND

Q15B

Q14

Q17

C2 40 pF

R14 350 kΩ

Q19

Q30

R22 150 kΩ

DENOTES CONNECTION ON MIC2950 ONLY

FEEDBACK

12 kΩ

Q21

Q29

Q31

RELAY

R18 20kΩ

100 x

Q24

Q26

Q25

R17

Q22

R15 100 kΩ

R16

R17

30 kΩ

10 Ω

Q28

R21 8 Ω

R23 60 kΩ

R24 50 kΩ

OUT

SENSE

R27 182 kΩ

5V TAP

R28 60 kΩ

Q23

SHDN

3-62 February 1999