Micrel MIC2954 250ma low-dropout regulator Datasheet

MIC2954
250mA Low-Dropout Regulator
General Description
Features
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 logiccompatible shutdown input is provided which enables the
regulator to be switched on and off. This part may be pinstrapped 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.
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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 SOT223 and SOIC-8 packages
Applications
• Battery powered equipment
• Cellular telephones
• Laptop, notebook, and palmtop computers
• PCMCIA VCC and VPP 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
Pb-Free /
Standard
RoHS Compliant
MIC2954-02BT
MIC2954-02WT*
MIC2954-03BT
MIC2954-03WT*
MIC2954-02BS
MIC2954-02WS*
MIC2954-03BS
MIC2954-03WS*
MIC2954-02BZ
MIC2954-02YZ
MIC2954-03BZ
MIC2954-03YZ
MIC2954-07BM
MIC2954-07YM
MIC2954-08BM
MIC2954-08YM
Accuracy
0.5%
1.0%
0.5%
1.0%
0.5%
1.0%
0.5%
1.0%
Junction
Temp. Range
–40° to +125°C
–40° to +125°C
–40° to +125°C
–40° to +125°C
–40° to +125°C
–40° to +125°C
–40° to +125°C
–40° to +125°C
Package
TO-220-3
TO-220-3
SOT-223-3
SOT-223-3
TO-92-3**
TO-92-3**
8-Pin SOIC
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. • 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
Micrel, Inc.
MIC2954
Typical Application
100k
VIN
VOUT
1.2V to 30V
MIC2954
8
3
SHUTDOWN
ENABLE
VERR
IN
OUT
SHDN ERR
1
FB
7
GND
R1
VOUT = VREF ⎛⎜1+ ⎞⎟
⎝ R2 ⎠
4
R1
5
VREF
100pF
10µF
R2
2, 6 = OPEN
5V Fixed Regulator
Adjustable Regulator
5V or 3V Selectable Regulator with Shutdown
Wide Input-Voltage-Range Current Limiter
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MIC2954
Pin Configuration
OUT 1
8 IN
SNS 2
7 FB
SHDN 3
6 TAP
GND 4
5 ERR
1
IN
3
3-Pin SOT-223 (S)
TO-92
3
OUT
2
GND
1
IN
TAB
8-Pin SOIC (M)
2
GND OUT
3-Pin TO-92 (Z)
3
OUT
2
GND
1
IN
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
8
1
1
1
IN
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 (VOUT = 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 (VOUT) 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).
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Pin Name
Supply Input.
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Micrel, Inc.
MIC2954
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VIN) ....................................... –20V to +60V
Feedback Voltage (VFB) (14, 15)........................ –1.5V to +26V
Shutdown Input Voltage (VSHDN).................... –0.3V to +30V
Error Output Voltage (VERR) .......................... –0.3V to +30V
Power Dissipation (PD) (4) ..........................Internally Limited
Lead Temperature (soldering, 5 sec.)........................ 260°C
Storage Temperature (Ts) .........................–65°C to +150°C
ESD Rating(3)
Supply Voltage (VIN)...................................... +2.0V to +30V
Junction Temperature (TJ) ........................ –40°C to +125°C
Package Thermal Resistance (θJC, θJA) (5)
Electrical Characteristics
MIC2954-07/08: VFB = VTAP; VSNS = VOUT; VSHDN ≤ 0.6V. All versions: VIN = 6V; IL = 1mA; CL = 2.2µF; TJ = 25°C,
bold values indicate –40°C ≤ TJ ≤ +125°C; Note 8; unless noted.
Symbol
Parameter
Condition
VOUT
Output Voltage
MIC2954-02/-07 (±0.5%)
∆VOUT/∆T
∆VOUT/VOUT
∆VOUT/VOUT
VIN – VOUT
IGND
IGND(DO)
Min
Typ
Max
Units
4.975
4.940
5.000
5.025
5.060
V
V
MIC2954-02/-07 (±0.5%), 1mA ≤ IL ≤ 250mA
4.930
5.000
5.070
V
MIC2954-03/-08 (±1%)
4.950
4.900
5.000
5.050
5.100
V
V
MIC2954-03/-08 (±1%), 1mA ≤ IL ≤ 250mA
4.880
5.000
5.120
V
Output Voltage Temperature
Coefficient, Note 6
MIC2954-02/-07 (±0.5%)
20
100
ppm/°C
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
0.20
%/V
%/V
MIC2954-03/-08 (±1%), VIN = 6V to 26V
0.03
0.20
0.40
%/V
%/V
MIC2954-02/-07 (±0.5%), IL = 1 to 250mA
0.04
0.16
0.20
%/V
%/V
MIC2954-03/-08 (±1%), IL = 1 to 250mA
0.04
0.20
0.30
%/V
%/V
IL = 1mA
60
100
150
mV
mV
IL = 50mA
220
250
420
mV
mV
IL = 100mA
250
300
450
mV
mV
IL = 250mA
375
450
600
mV
mV
IL = 1mA
140
200
300
µA
µA
IL = 50mA
0.5
1
2
mA
mA
IL = 100mA
1.7
2.5
3.5
mA
mA
IL = 250mA
5
9
12
mA
mA
VIN = 4.5V
180
300
µA
Load Regulation, Note 8
Dropout Voltage, Note 9
Ground Pin Current, Note 10
Ground Pin Current at Dropout,
Note 10
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MIC2954
Symbol
Parameter
Condition
ILIMIT
Current Limit, Note 11
VOUT = 0V
∆VOUT/∆PD
Thermal Regulation, Note 12
en
Output Noise Voltage
(10Hz to 100kHz)
IL = 100mA, CL = 2.2µF
Reference Voltage
MIC2954-02/-07 (±0.5%)
1.220
1.200
1.235
1.250
1.260
V
V
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
MIC2954-03/-08 (±1%), Note 13
1.185
Reference Voltage
Min
0.05
Max
Units
750
800
mA
mA
0.2
%/W
400
IL = 100mA, CL = 33µF
µVRMS
260
Feedback Pin Bias Current
Reference Voltage
Temperature Coefficient,
Note 12
Typ
20
µVRMS
1.285
V
40
60
nA
nA
MIC2954-02/-07 (±0.5%)
20
ppm/°C
MIC2954-03/-08 (±1%)
50
ppm/°C
Feedback Pin Bias Current
Temperature Coefficient
0.1
40
nA/°C
Error Comparator
Output Leakage Current
VOH = 30V
0.01
1.00
2.00
µA
µA
Output Low Voltage
VIN = 4.5V, IOL = 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
Input Logic Voltage
low (on)
1.3
high (off)
Shutdown Pin Input Current
Regular Output Current in
Shutdown
September 2007
0.7
2.0
V
V
VSHDN = 2.4V
30
50
100
µA
µA
VSHDN = 30V
450
600
750
µA
µA
3
10
20
µA
µA
Note 15
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Micrel, Inc.
MIC2954
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. PD(max) = (TJ(max) – TA) ÷ θJC. Exceeding TJ(max) will cause thermal shutdown.
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
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”).
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 IL = 1mA. For IL = 100µA and TJ = 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 (VOUT = 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 VIN = 20V (a 4W pulse) for t = 10ms.
13. VREF ≤ VOUT ≤ (VIN – 1V), 2.3V ≤ VIN ≤ 30V, 100 µA < IL ≤ 250 mA, TJ ≤ TJ(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 = VOUT /VREF = (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 VOUT as VOUT is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.
15. VSHDN ≥ 2V, VIN ≤ 30 V,VOUT = 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.
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MIC2954
Typical Characteristics
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MIC2954
Typical Characteristics
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MIC2954
Functional Diagrams
Unregulated
DC Supply
IN
OUT
5V/250mA
Output
Error
Amp.
182k
62k
2.2µF
1.23V
REF.
GND
MIC2954-02/-03
MIC2954-02 and MIC2954-03
MIC2954-07 and MIC2954-08
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Micrel, Inc.
MIC2954
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.
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 MIC295407/-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.
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 ⎞
⎛
VOUT = VREF ⎜1 +
⎟ + IFB R1
R2 ⎠
⎝
where:
VREF = nominal 1.235V reference voltage
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 VOUT 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) opencircuited, this is a negligible addition.
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 VOUT = 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.
September 2007
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 160µVRMS 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:
C BYPASS ≅
10
1
2πR1 × 200Hz
M9999-090607
Micrel, Inc.
MIC2954
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
θJA
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.
* 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
100µVrms 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.
Pad Layout (minimum recommended geometry)
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.
September 2007
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.
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MIC2954
Schematic Diagram
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MIC2954
Package Information
8-Pin SOIC (M)
0.090 (2.286) Radius, t yp.
2
3
1
0.145 (3.683)
0.135 (3.429)
0.055 (1.397)
0.045 (1.143)
10° typ.
BOTTOM VIEW
0.085 (2.159) Diam.
0.185 (4.699)
0.175 (4.445)
5° typ.
0.185 (4.699)
0.175 (4.445)
0.090 (2.286) typ.
5° typ.
Seat ing Plane
0.025 (0.635) Max
Uncont rolled
Lead Diamet er
0.500 (12.70) Min.
0.016 (0.406)
0.014 (0.356)
0.0155 (0.3937)
0.0145 (0.3683)
0.055 (1.397)
0.045 (1.143)
0.105 (2.667)
0.095 (2.413)
3-Pin TO-92 (Z)
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MIC2954
3-Pin SOT-223 (S)
3-Pin TO-220 (T)
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MIC2954
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.
September 2007
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