October 2003 1 MIC5271
MIC5271 Micrel
MIC5271
µCap Negative Low-Dropout Regulator
General Description
The MIC5271 is a µCap 100mA negative regulator in a
SOT-23-5 package. With better than 2% initial accuracy, this
regulator provides a very accurate supply voltage for applica-
tions that require a negative rail. The MIC5271 sinks 100mA
of output current at very low dropout voltage (600mV maxi-
mum at 100mA of output current).
The µCap regulator design is optimized to work with low-
value, low-cost ceramic capacitors. The output typically re-
quires only a 1µF capacitance for stability.
Designed for applications where small packaging and effi-
ciency are critical, the MIC5271 combines LDO design exper-
tise with IttyBitty packaging to improve performance and
reduce power dissipation. Ground current is optimized to help
improve battery life in portable applications. The MIC5271
also includes a TTL-compatible enable pin, allowing the user
to put the part into a zero-current off-mode.
The MIC5271 is available in the SOT-23-5 package for space
saving applications and it is available with an adjustable
output.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Typical Application
Features
•Stable with ceramic or tantalum capacitor
•Positive and negative enable thresholds
•Low dropout voltage: 500mV @ 100mA
•Low ground current: 35µA @ load = 100µA
•Tight initial accuracy: ±2%
•Tight load and line regulation
•Thermal shutdown
•Current limiting
• IttyBitty SOT-23-5 packaging
•Zero-current off-mode
Applications
•GaAsFET bias
•Portable cameras and video recorders
•PDAs
•Battery-powered equipment
•Post-regulation of DC-DC converters
IttyBitty is a registered trademark of Micrel, Inc.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
Ordering Information
Part Number Marking Voltage* Junction Temp. Range Package
MIC5271BM5 L9AA Adj. –40°C to +125°CSOT-23-5
MIC5271-3.0BM5 L930 –3.0V –40°C to +125°CSOT-23-5
MIC5271-5.0BM5 L950 –5.0V –40°C to +125°CSOT-23-5
*For other voltage options, please contact Micrel Marketing.
MIC5271BM5
GND
EN
–OUT–IN
1µF 10µF–5.0V
–6.0V
VIN
2
5
1
4
3
V
R1
R2
OUT
ADJ
Regulator With Adjustable Output
-5
-4
-3
-2
-1
0
1
2
3
4
5
-3 -5 -7 -9 -11 -13 -15
ENABLE VOLTAGE (V)
SUPPLY VOLTAGE (V)
Enable Input
Re
g
ulator On
Re
g
ulator On
Regulator Off
MIC5271 Micrel
MIC5271 2 October 2003
Pin Configuration
EN
–IN–OUT
ADJ
L9AA
13
45
2
GND
MIC5271BM5
Adjustable Output Voltage
Pin Description
Pin Number Pin Name Pin Function
(Adj.)
1ENEnable Input. TTL logic compatible enable input. Logic High = ON, Logic
Low or open = OFF.
2GND Ground.
3ADJ Adjustable (Input): Adjustable feedback output connects to resistor voltage
divider.
4–OUT Negative Regulator Output.
5–IN Negative Supply Input.
October 2003 3 MIC5271
MIC5271 Micrel
Absolute Maximum Ratings (Note 1)
Input Voltage (V–IN)...................................... –20V to +0.3V
Enable Voltage (VEN).................................... –20V to +20V
Power Dissipation (PD)............................Internally Limited
Junction Temperature (TJ) .......................–40°C to +125°C
Lead Temperature (soldering, 5 sec.) ....................... 260°C
Storage Temperature (TS) .......................–65°C to +150°C
ESD Rating, Note 3
Operating Ratings (Note 2)
Input Voltage (VIN)....................................... –16V to –3.3V
Enable Voltage (VEN).................................... –16V to +16V
Junction Temperature (TJ) .......................–40°C to +125°C
Thermal Resistance (θJA) Note 4 .........................235°C/W
Electrical Characteristics (Note 5)
VIN = VOUT – 1.0V; COUT = 4.7µF, IOUT = 100µA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; unless noted.
Symbol Parameter Condition Min Typ Max Units
VOUT Output Voltage Accuracy Variation from nominal VOUT –2 2 %
–3 3 %
∆VOUT/∆TOutput Voltage Temperature Note 6 100 ppm/°C
Coefficient
∆VOUT/VOUT Line Regulation VIN = VOUT – 1V to –16V 0.04 0.15 %/V
0.2
∆VOUT/VOUT Load Regulation IOUT = 100µA to 100mA, Note 7 0.4 1.8 %
2.0 %
VIN – VOUT Dropout Voltage, Note 8 IOUT = 100µA55mV
IOUT = 50mA 360 500 mV
IOUT = 100mA 500 700 mV
900
IGND Ground Current, Note 9 IOUT = 100µA25100 µA
IOUT = 50mA 0.9 mA
IOUT = 100mA 2.0 3.0 mA
IGND_SD Ground current in shutdown VEN = ±0.6V –1.0 0.1 +1.0 µA
PSRR Ripple Rejection f = 120Hz 50 dB
ILIMIT Current Limit VOUT = 0V 235 350 mA
Enable Input
TON Turn-on Time Time to VOUT = 90% nom. 60 µs
VEN Input Low voltage Regulator OFF ±0.6 V
Input High Voltage Regulator ON ±2.0 V
IEN Enable Input Current VEN = ± 0.6V and –2.0V 0.1 µA
VEN = +2.0V 5.6 10.0
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. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(max), the junction-to-ambient thermal
resistance, θJA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using:
PD(max) = (TJ(max) –T
A) / θJA, where θJA is 235°C/W. Exceeding the maximum allowable power dissipation will result in excessive die
temperature, and the regulator will go into thermal shutdown. See the
“Thermal Considerations”
section for details.
Note 5. Specification for packaged product only.
Note 6. Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 7. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are tested for load regulation in the load
range from 100µA to 100mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification.
Note 8. Dropout voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured at 1V
differential.
Note 9. Ground pin current is the regulator quiescent current plus pass transistor base current. The total current drawn from the supply is the sum of
the load current plus the ground pin current.
MIC5271 Micrel
MIC5271 4 October 2003
Typical Characteristics
0
-0.5
-1
-1.5
-2
-2.5
-3
-3.5
0-1-2-3-4-5
OUTPUT VOLTAGE (V)
SUPPLY VOLTAGE (V)
Dropout
Characteristics
0 Load
-100mA Load
-3.26
-3.265
-3.27
-3.275
-3.28
-3.285
-3.29
-3.295
-3.3
-3.305
0-20-40-60 -80 -100
OUTPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
Output Voltage
vs. Out
p
ut Current
-3.2
-3.22
-3.24
-3.26
-3.28
-3.3
-3.32
-3.34
-3.36
-3.38
-3.4
-40 -20 0 20 40 60 80 100120
OUTPUT VOLTAGE (V)
TEMPERATURE (°C)
Output Voltage
vs. Temperature
0
-0.5
-1
-1.5
-2
-2.5
0-20-40-60 -80 -100
GROUND CURRENT (mA)
OUTPUT CURRENT (mA)
Ground Current
vs. Output Current
5V
IN
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
0-1-2-3-4-5
GROUND CURRENT (µA)
SUPPLY VOLTAGE (V)
Ground Current
Characteristics
0µA Load
-100µA Load
-1mA Load
0
-0.5
-1
-1.5
-2
-2.5
0-1-2-3-4-5
GROUND CURRENT (mA)
SUPPLY VOLTAGE (V)
Ground Current
Characteristics
-100mA Load
-50mA Load
-10mA Load
0
-5
-10
-15
-20
-25
-30
-40 -20 0 20 40 60 80 100 120
GROUND CURRENT (µA)
TEMPERATURE (°C)
Ground Current
vs. Tem
p
erature
0A Load
-1mA Load
0
-0.5
-1
-1.5
-2
-2.5
-3
-3.5
-40 -20 0 20 40 6080100120
GROUND CURRENT (µA)
TEMPERATURE (°C)
Ground Current
vs. Tem
p
erature
-50A Load
-100mA Load
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
-4 -7 -10 -13 -16
ENABLE THRESHOLD (V)
SUPPLY VOLTAGE (V)
Positive Enable Threshold
vs. Su
pp
l
y
Volta
g
e
Enable Off
Enable On
0
-0.2
-0.4
-0.6
-0.8
-1
-1.2
-1.4
-1.6
-4 -7 -10 -13 -16
ENABLE THRESHOLD (V)
SUPPLY VOLTAGE (V)
Negative Enable Threshold
vs. Supply Volta
g
e
Enable Off
Enable On
0
-100
-200
-300
-400
-500
-600
0 -20 -40 -60 -80 -100
DROPOUT VOLTAGE (mV)
OUTPUT CURRENT (mA)
Dropout
vs. Out
p
ut Current
0
-50
-100
-150
-200
-250
-300
-350
-400
-40 -20 0 20 40 60 80 100120
DROPOUT VOLTAGE (mV)
TEMPERATURE (°C)
Dropout
vs. Temperature
0A Load
-10mA Load
October 2003 5 MIC5271
MIC5271 Micrel
Typical Characteristics (continued)
0
-100
-200
-300
-400
-500
-600
-700
-40 -20 0 20 40 60 80 100 120
DROPOUT VOLTAGE (mV)
TEMPERATURE (°C)
Dropout
vs. Temperature
-50mA Load
-100mA Load
MIC5271 Micrel
MIC5271 6 October 2003
Functional Characteristics
Load Transient
TIME (2ms/div.)
-100mA
C
OUT
= 1µF Ceramic
V
IN
= 5V
V
OUT
= 3V
-10mA
Output Current
(50mA/div.) V
OUT
(10mV/div.)
Load Transient
TIME (2ms/div.)
-100mA C
OUT
= 1µF Ceramic
V
IN
= 5V
V
OUT
= 3V
-10mA
Output Current
(50mA/div.) V
OUT
(10mV/div.)
  
TIME (20
m
s/div.)
0V
0V
Enable
(1V/div.) V
OUT
(1V/div.)
  
TIME (20
m
s/div.)
0V
0V
Enable
(1V/div.) V
OUT
(1V/div.)
October 2003 7 MIC5271
MIC5271 Micrel
Functional Diagram
VIN
VEN VOUT
A
DJ
GND
MIC5271-x.x
MIC5271 Micrel
MIC5271 8 October 2003
Applications Information
The MIC5271 is a general-purpose negative regulator that
can be used in any system that requires a clean negative
voltage from a negative output. This includes post regulating
of DC-DC converters (transformer based or charge pump
based voltage converters). These negative voltages typically
require a negative low dropout voltage regulator to provide a
clean output from typically noisy lines.
Input Capacitor
A 1µF input capacitor should be placed from IN to GND if
there is more than 2 inches of wire or trace between the input
and the AC filter capacitor, or if a battery is used as the input.
Output Capacitor
The MIC5271 requires an output capacitor for stable opera-
tion. A minimum of 1µF of output capacitance is required. The
output capacitor can be increased without limitation to im-
prove transient response. The output does not require ESR
to maintain stability, therefore a ceramic capacitor can be
used. High-ESR capacitors may cause instability. Capacitors
with an ESR of 3Ω or greater at 100kHz may cause a high
frequency oscillation.
Low-ESR tantalums are recommended due to the tight ca-
pacitance tolerance over temperature.
Ceramic chip capacitors have a much greater dependence
on temperature, depending upon the dielectric. The X7R is
recommended for ceramic capacitors because the dielectric
will change capacitance value by approximately 15% over
temperature. The Z5U dielectric can change capacitance
value by as much 50% over temperature, and the Y5V
dielectric can change capacitance value by as much as 60%
over temperature. To use a ceramic chip capacitor with the
Y5V dielectric, the value must be much higher than a tanta-
lum to ensure the same minimum capacitor value over
temperature.
No-Load Stability
The MIC5271 does not require a load for stability.
Enable Input
The MIC5271 comes with an enable pin that allows the
regulator to be disabled. Forcing the enable pin higher than
the negative threshold and lower than the positive threshold
disables the regulator and sends it into a “zero” off-mode
current state. In this state, current consumed by the regulator
goes nearly to zero. The MIC5271 will be in the on mode when
the voltage applied to the enable pin is either greater than the
positive threshold or less than the negative threshold.
-5
-4
-3
-2
-1
0
1
2
3
4
5
-3 -5 -7 -9 -11 -13 -15
ENABLE VOLTAGE (V)
SUPPLY VOLTAGE (V)
Enable Input
Re
g
ulator On
Re
g
ulator On
Regulator Off
Thermal Considerations
Absolute values will be used for thermal calculations to clarify
the meaning of power dissipation and voltage drops across
the part.
Proper thermal design for the MIC5271-5.0BM5 can be
accomplished with some basic design criteria and some
simple equations. The following information must be known
to implement your regulator design:
VIN = input voltage
VOUT = output voltage
IOUT = output current
TA = ambient operating temperature
IGND = ground current
Maximum power dissipation can be determined by knowing
the ambient temperature, TA, the maximum junction tem-
perature, 125°C, and the thermal resistance, junction to
ambient. The thermal resistance for this part, assuming a
minimum footprint board layout, is 235°C/W. The maximum
power dissipation at an ambient temperature of 25°C can be
determined with the following equation:
PTT
D(max) J(max) A
JA
=−
θ
P125 C 25 C
235 C/W
D(max) =°−°
°
P 425mW
D(max) =
The actual power dissipation of the regulator circuit can be
determined using one simple equation.
PD =
(
VIN – VOUT
)
IOUT + VIN × IGND
Substituting PD(max), determined above, for PD and solving
for the operating conditions that are critical to the application
will give the maximum operating conditions for the regulator
circuit. The maximum power dissipation number cannot be
exceeded for proper operation of the device. The maximum
input voltage can be determined using the output voltage of
5.0V and an output current of 100mA. Ground current, of 1mA
for 100mA of output current, can be taken from the “
Electrical
Characteristics ”
section of the data sheet.
425mW V 5.0V 100mA V 1mA
IN IN
=−
()
+×
425mW 100mA V 1mA V 500mW
IN IN
=×+×
()
−
925mW 101mA VIN
=×
V 9.16Vmax
IN =
Therefore, a –5.0V application at 100mA of output current
can accept a maximum input voltage of –9.16V in a SOT-23-5
package. For a full discussion of heat sinking and thermal
effects on voltage regulators, refer to Regulator Thermals
section of Micrel’s
“Designing with Low Dropout Voltage
Regulators”
handbook.
October 2003 9 MIC5271
MIC5271 Micrel
Adjustable Regulator Application
Figure 1. Adjustable Voltage Application
The MIC5271BM5 can be adjusted from 1.20V to 14V by
using two external resistors (Figure 1). The resistors set the
output voltage based on the following equation:
VOUT = VREF (1 +
R
R2
1
)
Where VREF = 1.20V
MIC5271 Micrel
MIC5271 10 October 2003
Package Information
0.20 (0.008)
0.09 (0.004)
0.60 (0.024)
0.10 (0.004)
3.02 (0.119)
2.80 (0.110) 10°
0°
3.00 (0.118)
2.60 (0.102)
1.75 (0.069)
1.50 (0.059)
0.95 (0.037) REF
1.30 (0.051)
0.90 (0.035)
0.15 (0.006)
0.00 (0.000)
DIMENSIONS:
MM (INCH)
0.50 (0.020)
0.35 (0.014)
1.90 (0.075) REF
SOT-23-5 (M5)
MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB http://www.micrel.com
The information furnished by Micrel in this datasheet 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 at Purchaser’s own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2003 Micrel, Incorporated.