MIC2954
250mA Low-Dropout Regulator
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
September 2007
M9999-090607
General Description
The MIC2954 is a “bulletproof” efficient voltage regulator
with very low dropout voltage (typically 40mV @ light loads
and 375mV @ 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, fold-back 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.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
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 SOIC-8 packages
Applications
• Battery powered equipment
• Cellular telephones
• Laptop, notebook, and palmtop computers
• PCMCIA V
CC
and V
PP
regulation/switching
• Bar code scanners
• Automotive electronics
• SMPS post-regulator/dc-to-dc modules
• Voltage reference
• High-efficiency linear power supplies
___________________________________________________________________________________________________________
Ordering Information
Part Number
Standard
Pb-Free /
RoHS Compliant Accuracy
Junction
Temp. Range Package
MIC2954-02BT MIC2954-02WT* 0.5% –40° to +125°C TO-220-3
MIC2954-03BT MIC2954-03WT* 1.0% –40° to +125°C TO-220-3
MIC2954-02BS MIC2954-02WS* 0.5% –40° to +125°C SOT-223-3
MIC2954-03BS MIC2954-03WS* 1.0% –40° to +125°C SOT-223-3
MIC2954-02BZ MIC2954-02YZ 0.5% –40° to +125°C TO-92-3**
MIC2954-03BZ MIC2954-03YZ 1.0% –40° to +125°C TO-92-3**
MIC2954-07BM MIC2954-07YM 0.5% –40° to +125°C 8-Pin SOIC
MIC2954-08BM MIC2954-08YM 1.0% –40° to +125°C 8-Pin SOIC
* RoHS compliant with ‘high-melting solder’ exemption.
** TO-92 package discontinuance notification issued September 2007. End-of-life-buy offered thru December 31, 2007.
Contact factory for additional information.
Micrel, Inc. MIC2954
September 2007
2 M9999-090607
Typical Application
SHUTDOWN
ENABLE
MIC2954
IN OUT
GND 10µF
V
IN
V
OUT
1.2V to 30V
SHDN
FB
R1
100pF R2
ERR
100
k
V
ERR
2, 6 = OPEN
1
3
8
5
7
4
V
REF
VV1
R1
R2
OUT REF
=+
⎛
⎝
⎜⎞
⎠
⎟
5V Fixed Regulator Adjustable Regulator
5V or 3V Selectable Regulator with Shutdown Wide Input-Voltage-Range Current Limiter
Micrel, Inc. MIC2954
September 2007
3 M9999-090607
Pin Configuration
1OUT
SNS
SHDN
GND
8IN
FB
TAP
ERR
7
6
5
2
3
4
123
IN GND OUT
8-Pin SOIC (M)
3-Pin SOT-223 (S)
1IN
2 GND
3 OUT
TO-92
TAB
3 OUT
2GN
D
1IN
3-Pin TO-92 (Z) 3-Pin TO-220 (T)
Pin Description
Pin No.
SOIC-8
Pin No.
SOT-223
Pin No.
TO-92
Pin No.
TO-220
Pin Name Pin Name
8 1 1 1 IN Supply Input.
4 2, TAB 2 2 GND Ground.
1 3 3 3 OUT Regulator Output.
2 SNS
Sense (Input): Output-sense-voltage end of internal resistive divider.
Connect to OUT (V
OUT
= 5V) for fixed5V operation; 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
OUT
) undervoltage condition.
(Low = error, floating = normal.)
6 TAP
Divider Tap (Output): Resistive voltage divider tap. With 5Vapplied to
SNS, VTAP is approximately 1.23V. Connect to FB for 5V operation.
Not used in adjustable configuration.
7 FB
Feedback (Input): Error amplifier input. Compared to internal1.23V
reference. Connect to external voltage divider for adjustable operation
or internal voltage divider (TAP) for 5V operation (see SNS, TAP).
Micrel, Inc. MIC2954
September 2007
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M9999-090607
Absolute Maximum Ratings(1)
Supply Voltage (V
IN
)....................................... –20V to +60V
Feedback Voltage (V
FB
)
(14, 15)
........................ –1.5V to +26V
Shutdown Input Voltage (V
SHDN
).................... –0.3V to +30V
Error Output Voltage (V
ERR
) .......................... –0.3V to +30V
Power Dissipation (P
D
)
(4)
..........................Internally Limited
Lead Temperature (soldering, 5 sec.)........................ 260°C
Storage Temperature (T
s
) .........................–65°C to +150°C
ESD Rating
(3)
Operating Ratings(2)
Supply Voltage (V
IN
)...................................... +2.0V to +30V
Junction Temperature (T
J
) ........................–40°C to +125°C
Package Thermal Resistance (θ
JC
, θ
JA
)
(5)
Electrical Characteristics
MIC2954-07/08: V
FB
= V
TAP
; V
SNS
= V
OUT
; V
SHDN
≤ 0.6V. All versions: V
IN
= 6V; I
L
= 1mA; C
L
= 2.2µF; T
J
= 25°C,
bold values indicate –40°C ≤ T
J
≤ +125°C; Note 8; unless noted.
Symbol Parameter Condition Min Typ Max Units
MIC2954-02/-07 (±0.5%) 4.975
4.940
5.000 5.025
5.060
V
V
MIC2954-02/-07 (±0.5%), 1mA ≤ I
L
≤ 250mA 4.930 5.000 5.070 V
MIC2954-03/-08 (±1%) 4.950
4.900
5.000 5.050
5.100
V
V
V
OUT
Output Voltage
MIC2954-03/-08 (±1%), 1mA ≤ I
L
≤ 250mA 4.880 5.000 5.120 V
MIC2954-02/-07 (±0.5%) 20 100
ppm/°C ∆V
OUT
/∆T Output Voltage Temperature
Coefficient, Note 6 MIC2954-03/-08 (±1%) 20 150
ppm/°C
MIC2954-02/-07 (±0.5%), V
IN
= 6V to 26V 0.03 0.10
0.20
%/V
%/V
∆V
OUT
/V
OUT
Line Regulation, Note 7
MIC2954-03/-08 (±1%), V
IN
= 6V to 26V 0.03 0.20
0.40
%/V
%/V
MIC2954-02/-07 (±0.5%), I
L
= 1 to 250mA 0.04 0.16
0.20
%/V
%/V
∆V
OUT
/V
OUT
Load Regulation, Note 8
MIC2954-03/-08 (±1%), I
L
= 1 to 250mA 0.04 0.20
0.30
%/V
%/V
Dropout Voltage, Note 9 I
L
= 1mA 60 100
150
mV
mV
I
L
= 50mA 220 250
420
mV
mV
I
L
= 100mA 250 300
450
mV
mV
V
IN
– V
OUT
I
L
= 250mA 375 450
600
mV
mV
Ground Pin Current, Note 10 I
L
= 1mA 140 200
300
µA
µA
I
L
= 50mA 0.5 1
2
mA
mA
I
L
= 100mA 1.7 2.5
3.5
mA
mA
I
GND
I
L
= 250mA 5 9
12
mA
mA
I
GND(DO)
Ground Pin Current at Dropout,
Note 10
V
IN
= 4.5V 180 300 µA
Micrel, Inc. MIC2954
September 2007
5
M9999-090607
Symbol Parameter Condition Min Typ Max Units
I
LIMIT
Current Limit, Note 11 V
OUT
= 0V 750
800
mA
mA
∆V
OUT
/∆P
D
Thermal Regulation, Note 12 0.05 0.2 %/W
I
L
= 100mA, C
L
= 2.2µF 400 µV
RMS
e
n
Output Noise Voltage
(10Hz to 100kHz) I
L
= 100mA, C
L
= 33µF 260 µV
RMS
MIC2954-02/-07 (±0.5%) 1.220
1.200
1.235 1.250
1.260
V
V
Reference Voltage
MIC2954-03/-08 (±1%) 1.210
1.200
1.235 1.260
1.270
V
V
MIC2954-02/-07 (±0.5%), Note 13 1.190 1.270 V Reference Voltage
MIC2954-03/-08 (±1%), Note 13 1.185 1.285 V
Feedback Pin Bias Current 20 40
60
nA
nA
MIC2954-02/-07 (±0.5%) 20 ppm/°C Reference Voltage
Temperature Coefficient,
Note 12 MIC2954-03/-08 (±1%) 50 ppm/°C
Feedback Pin Bias Current
Temperature Coefficient
0.1 40 nA/°C
Error Comparator
Output Leakage Current V
OH
= 30V 0.01 1.00
2.00
µA
µA
Output Low Voltage V
IN
= 4.5V, I
OL
= 400µA 150 250
400
mV
mV
Upper Threshold Voltage Note 14 60
40
25
mV
mV
Lower Threshold Voltage Note 14 75
95
140
mV
mV
Hysteresis Note 14 15 mV
mV
Shutdown Input
low (on) 1.3 0.7 V Input Logic Voltage
high (off) 2.0 V
V
SHDN
= 2.4V 30 50
100
µA
µA
Shutdown Pin Input Current
V
SHDN
= 30V 450 600
750
µA
µA
Regular Output Current in
Shutdown
Note 15 3
10
20
µA
µA
Micrel, Inc. MIC2954
September 2007
6
M9999-090607
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.
4. P
D(max)
= (T
J(max)
– T
A
) ÷ θ
JC
. Exceeding T
J(max)
will cause thermal shutdown.
5. Thermal resistance (θ
JC
) of the TO-220 package is 2.5°C/W, and 15°C/W for the SOT-223. Thermal resistance (θ
JC
) of the TO-92 package is
180°C/W with 0.4" leads and 160°C/W with 0.25" leads. Thermal resistance (θ
JA
) of the SOP-8 is 160°C/W mounted on a printed circuit board
(See “Application Information: Thermal Calculation”).
6. Output voltage temperature coefficient is defined as the worst case voltage change divide by the total temperature range.
7. Line regulation for the MIC2954 is tested at 125°C for I
L
= 1mA. For I
L
= 100µA and T
J
= 125°C, line regulation is guaranteed by design to0.2%.
See “Typical Characteristics” for line regulation versus temperature and load current.
8. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Changes in output voltage due to heating effects are
covered by the thermal regulation specification.
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
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.
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 pin
current.
11. The MIC2954 features fold-back current limiting. The short circuit (V
OUT
= 0V) current limit is less than the maximum current with normal output
voltage.
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 V
IN
= 20V (a 4W pulse) for t = 10ms.
13. V
REF
≤ V
OUT
≤ (V
IN
– 1V), 2.3V ≤ V
IN
≤ 30V, 100 µA < I
L
≤ 250 mA, T
J
≤ T
J(max)
.
14. Comparator thresholds are expressed in terms of a voltage differential at the FB pin below the nominal reference voltage measured at 6Vinput. To
express these thresholds in terms of output voltage change, multiply by the error amplifier gain = V
OUT
/V
REF
= (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 × 5V/1.235V = 384mV. Thresholds
remain constant as a percent of V
OUT
as V
OUT
is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.
15. V
SHDN
≥ 2V, V
IN
≤ 30 V,V
OUT
= 0, with the FB pin connected to TAP.
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.
17. Maximum positive supply voltage of 60V must be of limited duration (<10ms) and duty cycle (<1%). The maximum continuous supply voltage is 30V.
Micrel, Inc. MIC2954
September 2007
7
M9999-090607
Typical Characteristics
Micrel, Inc. MIC2954
September 2007
8
M9999-090607
Typical Characteristics
Micrel, Inc. MIC2954
September 2007
9
M9999-090607
Functional Diagrams
1.23V
REF.
Error
Amp.
182k
62k
GND
IN
Unregulated
DC Supply
MIC2954-02/-03
2.2µF
OUT 5V/250mA
Output
MIC2954-02 and MIC2954-03
MIC2954-07 and MIC2954-08
Micrel, Inc. MIC2954
September 2007
10
M9999-090607
Application 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 a12V
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
OUT
= 4.75). Since the
MIC2954-07/-08’s 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.
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:
R1I
R2
R1
1VV
FBREFOUT
+
⎟
⎠
⎞
⎜
⎝
⎛+=
where:
V
REF
= nominal 1.235V reference voltage
I
FB
= 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
RMS
for a
100kHz bandwidth at 5V output. Noise can be reduced
fourfold by a bypass capacitor across R1, since it
reduces the high frequency gain from 4 to unity.
Pick:
200HzR12
1
C
BYPASS
×
≅
π
Micrel, Inc. MIC2954
September 2007
11 M9999-090607
* See Application Information
Figure 1. /Error Output Timing
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 a100kHz 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 applica-
tions 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 pack-
age) has the following thermal characteristics when
mounted on a single layer copper-clad printed circuit
board.
PC Board Dielectric Material θ
JA
FR4 160°C/W
Ceramic 120°C/W
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)
Nominal Power Dissipation and Die Temperature
The MIC2954-07BM/-08BM at a 55°C ambient temp-
erature 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.
Micrel, Inc. MIC2954
September 2007
12 M9999-090607
Schematic Diagram
Micrel, Inc. MIC2954
September 2007
13 M9999-090607
Package Information
8-Pin SOIC (M)
3
2
1
10° typ.
5° typ.
5° typ.
0.185 (4.699)
0.175 (4.445)
0.185 (4.699)
0.175 (4.445)
0.085 (2.159) Diam.
0.500 (12.70) Min.
0.090 (2.286) typ.
0.0155 (0.3937)
0.0145 (0.3683)
Seating Plane
0.025 (0.635) Max
Uncontrolled
Lead Diam et er
0.016 (0.406)
0.014 (0.356)
0.105 (2.667)
0.095 (2.413)
0.055 (1.397)
0.045 (1.143)
0.090 (2.286) Radius, typ
.
0.145 (3.683)
0.135 (3.429)
0.055 (1.397)
0.045 (1.143)
BOTTOM VIEW
3-Pin TO-92 (Z)
Micrel, Inc. MIC2954
September 2007
14 M9999-090607
3-Pin SOT-223 (S)
3-Pin TO-220 (T)
Micrel, Inc. MIC2954
September 2007
15 M9999-090607
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.
© 2001 Micrel, Incorporated.
