Datasheet MIC2954-03BZ, MIC2954-07BM, MIC2954-08BM, MIC2954-03BT, MIC2954-02BS Datasheet (MICREL)

MIC2954 Micrel

SHUTDOWN

ENABLE

MIC2954

IN OUT

GND

10µF

V

IN

V

OUT

1.2V to 30V

SHDN

FB

R1

100pF

R2

ERR

100k V

ERR

2, 6 = OPEN

1

3

8

5
7

4

V

REF

VV1

R1

R2

OUT

REF

=+











SHUTDOWN

ENABLE

MIC2954-07/-08

IN OUT

GND

V

IN

V

OUT

≈ VIN*

SHDN

FB

ERR

* MINIMUM INPUT-TO-OUTPUT

VOLTAGE RANGES FROM
40mV TO 400mV DEPENDING
UPON LOAD CURRENT

1

3

8

5
7

4

MIC2954

250mA Low-Dropout Regulator

General Description

The MIC2954 is a “bulletproof” efficient voltage regulator with
very low dropout voltage (typically 40mV at light loads and
375mV at 250mA), and low quiescent current (120µA typi­cal). The quiescent current of the MIC2954 increases only
slightly in dropout, thus prolonging battery life. Key MIC2954
features include protection against reversed battery, fold­back current limiting, and automotive load dump protection
(60V positive transient).

The MIC2954-07/08BM is an adjustable version that includes
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 provided which enables the regulator to be switched on and
off. This part may be pin-strapped for 5V output, or pro­grammed from 1.24V to 29V with the use of two external
resistors.

The MIC2954 is available in two voltage tolerances, ±0.5%
maximum and ±1% maximum. Both are guaranteed for
junction temperatures from –40°C to +125°C.

The MIC2954 has a very low output voltage temperature
coefficient and extremely good load and line regulation
(0.04% typical).

Features

• High-accuracy 5V, guaranteed 250mA output

• Low quiescent current

• Low dropout voltage

• Extremely tight load and line regulation

• Very low temperature coefficient

• Current and thermal limiting

• Input can withstand –20V reverse battery and
+60V positive transients

• Error flag warns of low output voltage

• Logic-controlled electronic shutdown

• Output programmable from 1.24V to 29V
(MIC2954-07/08)

• Available in TO-220, TO-92, and surface-mount
SOT-223 and SOP-8 packages

Applications

• Battery powered equipment

• Cellular telephones

• Laptop, notebook, and palmtop computers

• PCMCIA VCC and V

• Bar code scanners

• Automotive electronics

• SMPS post-regulator/dc-to-dc modules

• Voltage reference

• High-efficiency linear power supplies

regulation/switching

PP

T ypical Applications

SHUTDOWN

ENABLE

5V or 3V Selectable Regulator with Shutdown

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 [phone] • fax + 1 [phone] • http://www.micrel.com

August 1999 1 MIC2954

IN

IN OUT

MIC2954

V

GND

5V Fixed Regulator

V

IN

MIC2954-07/-08

+7V

8

IN OUT

3

SHDN

GND

5V

3.3V

1
5

ERR

7

FB

220k

4

470k

Q1 ON = 3.3V

Q1 OFF = 5.0V

V

OUT

2.2µF

100pF

180k

1%

Q1
2N2222

1%

300k
1%

V

OUT

5V or 3.3V

3.3µF

Adjustable Regulator

Wide Input-Voltage-Range Current Limiter

MIC2954 Micrel

IN OUTGND

132

TAB

GND

Ordering Information

Part Number Accuracy Junc. Temp. Range Package

MIC2954-02BT 0.5% –40°C to +125°C TO-220
MIC2954-03BT 1.0% –40°C to +125°C TO-220
MIC2954-02BS 0.5% –40°C to +125°C SOT-223
MIC2954-03BS 1.0% –40°C to +125°C SOT-223
MIC2954-02BZ 0.5% –40°C to +125°C TO-92
MIC2954-03BZ 1.0% –40°C to +125°C TO-92
MIC2954-07BM 0.5% –40°C to +125°C SOP-8
MIC2954-08BM 1.0% –40°C to +125°C SOP-8

Pin Configuration

MIC2954

OUT
SNS

1
2

IN

8

FB

7

SHDN

GND

3
4

TAP

6
5

ERR

SOP-8 (M)

321

TAB

OUT IN

GND

TO-92 (Z)

Pin Description

Pin No. Pin No. Pin No. Pin No. Pin Name Pin Function

SOT-223 SOP-8 TO-220 TO-92

1 8 1 1 IN Supply Input

2, TAB 4 2 2 GND Ground

3 1 3 3 OUT Regulator Output

2 SNS Sense (Input): Output-sense-voltage end of internal resistive

divider. Connect to OUT (V
also see TAP. Not used in adjustable configuration.

3 SHDN Shutdown (Input): Active-low input enables regulator.

(Low = enable; high = shutdown.)

5 ERR Error Flag (Output): Open collector (active-low) output. Active

state indicates an output (V
(Low = error, floating = normal.)

6 TAP Divider Tap (Output): Resistive voltage divider tap. With 5V

7 FB Feedback (Input): Error amplifier input. Compared to internal

applied to SNS, V
FB for 5V operation. Not used in adjustable configuration.

1.23V reference. Connect to external voltage divider for
adjustable operation or internal voltage divider (TAP) for 5V
operation (see SNS, TAP).

SOT-223 (S)

TO-220 (T)

= 5V) for fixed 5V operation;

OUT

) undervoltage condition.

OUT

is approximately 1.23V. Connect to

TAP

3 OUT
2 GND
1IN

MIC2954 2 August 1999

MIC2954 Micrel

Absolute Maximum Ratings (Note 1)

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

Feedback Voltage (VFB), Note 14,15........... –1.5V to +26V

Shutdown Input Voltage (V
Error Output Voltage (V

ERR

) ................. –0.3V to +30V

SHDN

) ........................ –0.3V to +30V

Operating Ratings (Note 2)

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

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

Package Thermal Temperature (θ

)................ Note 5

JC, θJA

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

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

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

ESD, Note 3

Electrical Characteristics

MIC2954-07/08: VFB = V

bold values indicate –40°C ≤ TJ ≤ +125°C; Note 8; unless noted.
Symbol Parameter Conditions Min Typ Max Units

V

OUT

Output Voltage MIC2954-02/-07 (±0.5%) 4.975 5.000 5.025 V

TAP

; V

SNS

= V

OUT

; V

≤ 0.6V. All versions: VIN = 6V; IL = 1mA; CL = 2.2µF; TJ = 25°C,

SHDN

4.940 5.060 V
MIC2954-02/-07 (±0.5%), 1mA ≤ IL ≤ 250mA 4.930 5.000 5.070 V
MIC2954-03/-08 (±1%) 4.950 5.000 5.050 V

4.900 5.100 V
MIC2954-03/-08 (±1%), 1mA ≤ IL ≤ 250mA 4.880 5.000 5.120 V

∆V

/∆T Output Voltage MIC2954-02/-07 (±0.5%) 20 100 ppm/°C

OUT

∆V

OUT/VOUT

∆V

OUT/VOUT

V

– V

IN

I

GND

I

GND(DO)

OUT

Temperature Coefficient, Note 6

MIC2954-03/-08 (±1%) 20 150 ppm/°C

Line Regulation, Note 7 MIC2954-02/-07 (±0.5%), VIN = 6V to 26V 0.03 0.10 %/V

MIC2954-03/-08 (±1%), V

= 6V to 26V 0.03 0.20 %/V

IN

Load Regulation, Note 8 MIC2954-02/-07 (±0.5%), IL = 1 to 250mA, 0.04 0.16 %/V

MIC2954-03/-08 (±1%), I

= 1 to 250mA, 0.04 0.20 %/V

L

Dropout Voltage, Note 9 IL = 1mA 60 100 mV

I

= 50mA 220 250 mV

L

= 100mA 250 300 mV

I

L

= 250mA 375 450 mV

I

L

Ground Pin Current, Note 10 IL = 1mA 140 200 µA

I

= 50mA 0.5 1 mA

L

I

= 100mA 1.7 2.5 mA

L

I

= 250mA 5 9 mA

L

Ground Pin Current at Dropout, VIN = 4.5V 180 300 µA

Note 10

0.20 %/V

0.40 %/V

0.20 %/V

0.30 %/V

150 mV

420 mV

450 mV

600 mV

300 µA

2 mA

3.5 mA

12 mA

I

LIMIT

Current Limit, Note 11 V

= 0V 750 mA

OUT

800 mA

August 1999 3 MIC2954

MIC2954 Micrel

Symbol Parameter Conditions Min Typ Max Units

∆V

/∆P

OUT

e

n

Error Comparator

Shutdown Input

Thermal Regulation, Note 12 0.05 0.2 %/W

D

Output Noise Voltage IL = 100mA, CL = 2.2µF 400 µV(rms)
(10Hz to 100kHz)

IL = 100mA, CL = 33µF 260 µV(rms)

Reference Voltage MIC2954-02/-07 (±0.5%) 1.220 1.235 1.250 V

1.200 1.260 V

MIC2954-03/-08 (±1%) 1.210 1.235 1.260 V

1.200 1.270 V

Reference Voltage MIC2954-02/-07 (±0.5%), Note 13 1.190 1.270 V

MIC2954-03/-08 (±1%), Note 13 1.185 1.285 V

Feedback Pin Bias Current 20 40 nA

60 nA

Reference Voltage MIC2954-02/-07 (±0.5%) 20 ppm/°C
Temperature Coefficient, Note 12

MIC2954-03/-08 (±1%) 50 ppm/°C

Feedback Pin Bias Current 0.1 40 nA/°C
Temperature Coefficient

Output Leakage Current V

Output Low Voltage V

= 30V 0.01 1.00 µA

OH

= 4.5V, IOL = 400µA 150 250 mV

IN

2.00 µA

400 mV

Upper Threshold Voltage Note 14 60 40 mV

25 mV

Lower Threshold Voltage Note 14 75 95 mV

140 mV

Hysteresis Note 14 15 mV

Input Logic Voltage low (on) 1.3 0.7 V

high (off) 2.0 V

Shutdown Pin Input Current V

= 2.4V 30 50 µA

SHDN

100 µA

V

= 30V 450 600 µA

SHDN

750 µA

Regular Output Current in Note 15 310µA
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. P
Note 5. Thermal resistance (θJC) of the TO-220 package is 2.5°C/W, and 15°C/W for the SOT-223. Thermal resistance (θJC) of the TO-92 package is

Note 6. Output voltage temperature coefficient is defined as the worst case voltage change divide by the total temperature range.
Note 7. Line regulation for the MIC2954 is tested at 125°C for IL = 1mA. For IL = 100µA and TJ = 125°C, line regulation is guaranteed by design to

Note 8. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Changes in output voltage due to heating effects

Note 9. Dropout Voltage is defined as the input to output differential at which the output voltage drops 100 mV below its nominal value measured at 1V

Note 10. 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

= (T

D(max)

180°C/W with 0.4" leads and 160°C/W with 0.25" leads. Thermal resistance (θJA) of the SOP-8 is 160°C/W mounted on a printed circuit board
(See “Application Information: Thermal Calculation”).

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

are covered by the thermal regulation specification.

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

pin current.

– TA) ÷ θJC. Exceeding T

J(max)

will cause thermal shutdown.

J(max)

MIC2954 4 August 1999

MIC2954 Micrel

Note 11. The MIC2954 features fold-back current limiting. The short circuit (V

output voltage.

Note 12. 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 = 20V (a 4W pulse) for t = 10ms.

Note 13. V

REF

≤ V

≤ (VIN – 1V), 2.3V ≤ VIN ≤ 30V, 100 µA < IL ≤ 250 mA, TJ ≤ T

OUT

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

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

Note 15. V

≥ 2V, VIN ≤ 30 V,V

SHDN

= 0, with the FB pin connected to TAP.

OUT

Note 16. When used in dual supply systems where the regulator load is returned to a negative supply, the output voltage must be diode clamped to

ground.

Note 17. Maximum positive supply voltage of 60V must be of limited duration (<10ms) and duty cycle (<1%). The maximum continuous supply voltage

is 30V.

= 0V) current limit is less than the maximum current with normal

OUT

J(max).

/V

= (R1 + R2)/R2. For

REF

OUT

as V

OUT

is varied, with the dropout warning occurring at

OUT

August 1999 5 MIC2954

MIC2954 Micrel

T ypical Characteristics

Ground Pin Current

180
160
140
120
100

80
60
40

20

GROUND PIN CURRENT (µA)

0

012345678

I L = 1mA

INPUT VOLTAGE (V)

Ground Pin Current

400

300

200

I L = 1mA

100

0

GROUND PIN CURRENT (µA)

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

Ground Pin Current vs Load

100

10

1

0.1

GROUND PIN CURRENT (mA)

0.01

0.1 1 10 100
OUTPUT CURRENT (mA)

1000

Ground Pin Current

20
18

16
14
12

10

8
6
4

2

GROUND PIN CURRENT (mA)

0

012345678

INPUT VOLTAGE (V)

Ripple Rejection

100

90
80
70

60
50

V

=6V

IN

40

V

OUT

CL=2.2µF

30

RIPPLE REJECTION (dB)

20

0.01 0.1 1 10 100 1000
FREQUENCY (kHz)

I L = 250 mA

I L =1 mA

=5V

I L =10mA

Ground Pin Current

25

20

15

10

5

GROUND PIN CURRENT (mA)

0

-75 -50 -25 0 25 50 75 100125 150
JUNCTION TEMPERATURE (°C)

Ripple Rejection

90
80
70
60

50

I L = 250mA

40

V

=6V

IN

30

V

=5V

OUT

CL=10µF

20

RIPPLE REJECTION (dB)

10

0.01 0.1 1 10 100 1000
FREQUENCY (kHz)

I L = 250mA

I L = 100 mA

I L = 100 mA

Output Noise Voltage

500

400

300

200

100

NOISE VOLTAGE (µVrms)

100

RIPPLE REJECTION (dB)

CL = 2.2 µF

CL = 33 µF

V

IN

V

0

0.1 1 10 100
LOAD CURRENT (mA)

OUT

Ripple Rejection

90
80
70

60
50

V

=6V

IN

40

V

=5V

OUT

CL=2.2µF

30
20

0.01 0.1 1 10 100 1000
FREQUENCY (kHz)

I L = 0

I L = 100 µA

=6V

=5V

1000

Line Transient Response

400

0

-400

CHANGE (mV)

OUTPUT VOLTAGE

8V

INPUT

6V

VOLTAGE

0 0.2 0.4 0.6 0.8 1

TIME (mS)

CL=2.2µF
I L=10mA

V

=5V

OUT

CHANGE (mV)

OUTPUT VOLTAGE

INPUT

VOLTAGE

Line Transient Response

TIME (mS)

CL=33µF
I L=10mA

V

=5V

OUT

80
40

0

-40
8V

6V

012345

Output Impedance

100

I L=100µA

10

1

I L=10µA

0.1

OUTPUT IMPEDANCE ( Ω )

0.01

0.01

I L=250mA

0.1 1 10
FREQUENCY (kHz)

V

=6V

IN

V

OUT

CL=10µF

100

=5V

1000

MIC2954 6 August 1999

MIC2954 Micrel

Load Transient Response

800
400

0

-400

CHANGE (mV)

OUTPUT VOLTAGE

-800

250mA

100µA

LOAD

CURRENT

Enable Transient

10

8

CL=2.2µF

6
4

OUTPUT

VOLTAGE (mV)

2
0

2
0

SHUTDOWN

VOLTAGE (V)

CL=2.2µF

TIME (mS)

CL=33µF

I L=10mA
V
V

TIME (mS)

V
V

3020100

IN
OUT

3210

=6V

IN
OUT

40

=14V

=5V

=5V

Load Transient Response

200
100

0

-100

CHANGE (mV)

OUTPUT VOLTAGE

-200

250mA

100µA

LOAD

CURRENT

0

10 20 30 40 50 60

CL=33µF

TIME (mS)

V
V

IN
OUT

=6V

=5V

Dropout Characteristics

6
5
4
3
2
1

OUTPUT VOLTAGE (V)

0

I L=100µA

01 2345 6

INPUT VOLTAGE (VOLTS)

I L=250mA

Short Circuit and Maximum

Enable Transient

6

CL=2.2µF

4

2

OUTPUT

VOLTAGE (V)

0
2

0

4

5

SHUTDOWN

VOLTAGE (V)

CL=33µF

I L=10mA
V

IN

V

OUT

TIME (mS)

=6V

=5V

4

3210

5

Current vs. Temperature

700

V

= V

OUT

650
600
550
500
450

CURRENT (mA)

400
350
300

-60 -30 0 30 60 90 120 150

NOMINAL

V

OUT

3 SAMPLES
(HI/AVG/LO)

V

= 0V

OUT

TEMPERATURE (°C)

– 0.5V

= 3.3V

Thermal Regulation

15
10

5
0

CHANGE (V)

-5

OUTPUT VOLTAGE

4
2
0

POWER

DISSIPATION (W)

TIME (mS)

3020100

40

August 1999 7 MIC2954

MIC2954 Micrel

Block Diagrams

Unregulated
DC Supply

Unregulated
DC Supply

1.23V
REF.

MIC2954-02/-03

IN

Error

Amp.

182k

62k

MIC2954-02 and MIC2954-03

INFB

OUT

GND

OUT

5V/250mA
Output

2.2µF

5V/250mA
Output

SHDN

TTL/CMOS

Control Logic

Input

60mV

1.23V
REF.

MIC2954-07/-08

Error
Amp.

182k

60k

Error Detection

Comparator

MIC2954-07 and MIC2954-08

SNS

TAP

ERR

GND

330k

TTL/CMOS
Compatible
Error Output

MIC2954 8 August 1999

MIC2954 Micrel

C

2 R1 200Hz

BYPASS

≅

×

1

π

Applications Information

External Capacitors

A 2.2µF (or greater) capacitor is required between the MIC2954
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
1mA. Adjusting the MIC2954-07/-08 to voltages below 5V
runs the error amplifier at lower gains so that more output
capacitance is needed. For the worst-case situation of a
250mA load at 1.23V output (output shorted to feedback) a
5µF (or greater) capacitor should be used.

The MIC2954 will remain in regulation with a minimum load
of 1mA. When setting the output voltage of the MIC2954-07/

-08 version with external resistors, the current through these
resistors may be included as a portion of the minimum load.

A 0.1µF capacitor should be placed from the MIC2954 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.

Error Detection Comparator Output
(MIC2954-07/-08)

A logic-low output will be produced by the comparator when­ever the MIC2954-07/-08 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 MIC2954-07/-08. 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, or thermal limiting.

Figure 1 is a timing diagram depicting the ERR signal and the
regulated output voltage as the MIC2954-07/-08 input is
ramped up and down. The ERR signal becomes valid (low) at
about 1.3V input. It goes high at about 5V input (the input
voltage at which V
dropout voltage is load-dependent (see curve in “Typical
Characteristics”), the input voltage trip point (about 5V) will
vary with the load current. The output voltage trip point
(approximately 4.75V) 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 5V output
or some other supply voltage. In determining a value for this
resistor, note that while the output is rated to sink 400µA, 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.

= 4.75). Since the MIC2954-07/-08’s

OUT

Programming the Output Voltage
(MIC2954-07/-08)

The MIC2954-07/-08 may be pin-strapped for 5V using its
internal voltage divider by tying pin 1 (OUT) to pin 2 (SNS) and
pin 7 (FB) to pin 6 (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 3.

The complete equation for the output voltage is

R1

V=V

OUT

REF FB






11+

R2



+





I R

where:

V

= nominal 1.235V reference voltage

REF

IFB = nominal FB pin bias current (–20nA)

The minimum recommended load current of 1µA 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

OUT

which
may be eliminated 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 12µA.
Since the MIC2954-07/-08 typically draws 60µA at no load
with pin 2 (SNS) open-circuited, this is a negligible addition.

Reducing Output Noise

In reference 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 relatively inefficient, as increasing the
capacitor from 1µF to 220µF only decreases the noise from
430µV to 160µV

for a 100kHz bandwidth at 5V output.

RMS

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

Not

Valid

4.75V

1.3V

5V

Not

Valid

**

Output

Voltage

ERR

Input

Voltage

*See Application Information

Figure 1. Error Output Timing

August 1999 9 MIC2954

MIC2954 Micrel

or about 0.01µF. When doing this, the output capacitor must
be increased to 3.3µF to maintain stability. These changes
reduce the output noise from 430µV to 100µV rms for a
100kHz 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.

Automotive Applications

The MIC2954 is ideally suited for automotive applications for
a variety of reasons. It will operate over a wide range of input
voltages with very low dropout voltages (40mV at light loads),
and very low quiescent currents (75µA typical). These
features are necessary for use in battery powered systems,
such as automobiles. It is a “bulletproof” device 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.

Thermal Calculations

Layout Considerations

The MIC2954-07BM/-08BM (8-pin surface-mount package)
has the following thermal characteristics when mounted on a
single layer copper-clad printed circuit board.

PC Board Dielectric Material

FR4 160°C/W
Ceramic 120°C/W

θθ

θ

θθ

JA

Multilayer boards having a ground plane, wide traces near the
pads, and large supply bus lines provide better thermal
conductivity.

Our calculations will use the “worst case” value of 160°C/W,
which assumes no ground plane, minimum trace widths, and
a FR4 material board.

Pad Layout (minimum recommended geometry)

50 mil

245 mil

30 mil 50 mil

150 mil

Nominal Power Dissipation and Die Temperature

The MIC2954-07BM/-08BM at a 55°C ambient temperature
will operate reliably at up to 440mW power dissipation when
mounted in the “worst case” manner described above. This
power level is equivalent to a die temperature of 125°C, the
recommended maximum temperature for nonmilitary grade
silicon integrated circuits.

Schematic Diagram

Q42

50 kΩ

10 kΩ

Q40

IN

Q15A

R11

Q4Q3

18
kΩ

Q6

Q1

10

R1

20 kΩ

R2

50 kΩ

Q41

R30

30
kΩ

R3

50 kΩ

R5

180

kΩ

ERROR

Q5

C1

20
pF

Q13

R4

13 kΩ

R11

20.6
kΩ

Q2

R8

31.4 kΩ

R6

140

R9

27.8 kΩ

kΩ

Q12

Q37

Q38

R26
60 kΩ

Q39

Q7

Q11

Q9

Q8

R25

2.8 kΩ

Q34

Q20

R12
110

kΩ

R10
150

kΩ

Q36

Q18

Q16

R13
100

kΩ

GND

R22
150 kΩ

Q15B

Q17

C2
40 pF

R14
350
kΩ

FEEDBACK

Q25

R17

Q14

12 kΩ

Q21

Q19

Q31

Q30

DENOTES CONNECTION ON
MIC2954-02Bx/-03Bx ONLY

Q22

R15
100 kΩ

R16
30 kΩ

Q29

Q28

R21 8 Ω

R23 60 kΩ

R24
50 kΩ

R18
20kΩ

Q26

10 Ω

Q24

OUT

SENSE

R27
182 kΩ

5V TAP

R28
60 kΩ

Q23

R17

SHDN

MIC2954 10 August 1999

MIC2954 Micrel

Package Information

0.151 D ±0.005

0.108 ±0.005
(2.74 ±0.13)

0.818 ±0.005

(20.78 ±0.13)

(3.84 D ±0.13)

0.410 ±0.010

(10.41 ±0.25)

0.356 ±0.005
(9.04 ±0.13)

0.176 ±0.005
(4.47 ±0.13)

0.590 ±0.005
(14.99 ±0.13)

0.050 ±0.005
(1.27 ±0.13)

7°

0.050 ±0.003
(1.27 ±.08)

0.100 ±0.005
(2.54 ±0.13)

0.090 (2.286) Radius, typ.

10° typ.

1

BOTTOM VIEW

0.185 (4.699)

0.175 (4.445)

0.030 ±0.003
(0.76 ±0.08)

TO-220 (T)

2

3

0.055 (1.397)

0.045 (1.143)

0.085 (2.159) Diam.

1.140 ±0.010
(28.96 ±0.25)

0.018 ±0.008
(0.46 ±0.020)

0.145 (3.683)

0.135 (3.429)

7°

3°

0.100 ±0.020
(2.54 ±0.51)

DIMENSIONS:

5° typ.

INCH
(MM)

0.185 (4.699)

0.175 (4.445)

0.090 (2.286) typ.

Seating Plane

0.016 (0.406)

0.014 (0.356)

0.055 (1.397)

0.045 (1.143)

0.105 (2.667)

0.095 (2.413)

0.025 (0.635) Max
Uncontrolled
Lead Diameter

0.500 (12.70) Min.

0.0155 (0.3937)

0.0145 (0.3683)

5° typ.

TO-92 (Z)

August 1999 11 MIC2954

MIC2954 Micrel

0.026 (0.65)
MAX)

PIN 1

0.157 (3.99)

0.150 (3.81)

0.050 (1.27)

0.064 (1.63)

0.045 (1.14)

2.41 (0.095)

2.21 (0.087)

4.7 (0.185)

4.5 (0.177)

0.10 (0.004)

0.02 (0.0008)

TYP

0.197 (5.0)

0.189 (4.8)

3.15 (0.124)

2.90 (0.114)

C

L

0.020 (0.51)

0.013 (0.33)

0.0098 (0.249)

0.0040 (0.102)

SEATING

C

L

6.70 (0.264)

6.30 (0.248)

0°–8°

PLANE

SOP-8 (M)

3.71 (0.146)

3.30 (0.130)

1.04 (0.041)

0.85 (0.033)

1.70 (0.067)

1.52 (0.060)
10°

MAX

DIMENSIONS:
INCHES (MM)

0.050 (1.27)

0.016 (0.40)

0.244 (6.20)

0.228 (5.79)

7.49 (0.295)

6.71 (0.264)

16°
10°

45°

0.010 (0.25)

0.007 (0.18)

DIMENSIONS:

MM (INCH)

0.038 (0.015)

0.25 (0.010)

0.84 (0.033)

0.64 (0.025)

0.91 (0.036) MIN

SOT-223 (S)

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

TEL + 1 [phone] FAX + 1 [phone] 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.

© 1999 Micrel Incorporated

MIC2954 12 August 1999