April 2005 1 M9999-041205
MIC5238 Micrel, Inc.
MIC5238
Ultra-Low Quiescent Current, 150mA
µ
Cap LDO Regulator
General Description
The MIC5238 is an ultra-low voltage output, 150mA LDO
regulator. Designed to operate in a single supply or dual
supply mode, the MIC5238 consumes only 23µA of bias
current, improving efficiency. When operating in the dual
supply mode, the efficiency greatly improves as the higher
voltage supply is only required to supply the 23µA bias
current while the output and base drive comes off of the much
lower input supply voltage.
As a µCap regulator, the MIC5238 operates with a 2.2µF
ceramic capacitor on the output, offering a smaller overall
solution. It also incorporates a logic-level enable pin that
allows the MIC5238 to be put into a zero off-current mode
when disabled.
The MIC5238 is fully protected with current limit and thermal
shutdown. It is offered in the IttyBitty™ SOT-23-5 package
with an operating junction temperature range of
–40°C to +125°C.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
IttyBitty is a trademark of Micrel, Inc.
Features
•Ultra-low input voltage range: 1.5V to 6V
•Ultra-low output voltage: 1.1V minimum output voltage
•Low dropout voltage: 310mV at 150mA
•High output accuracy: ±2.0% over temperature
•µCap: stable with ceramic or tantalum capacitors
•Excellent line and load regulation specifications
•Zero shutdown current
•Reverse leakage protection
•Thermal shutdown and current limit protection
•IttyBitty™ SOT-23-5 package
Applications
•PDAs and pocket PCs
•Cellular phones
•Battery powered systems
•Low power microprocessor power supplies
Typical Application
15
2
34
C
OUT
=2.2µF
ceramic
C
IN
V
BIAS
=2.5V
EN
MIC5238-1.0BM5
V
IN
=1.5V 1.0V
C
BIAS
OFF
ON
Ultra-Low Voltage Application
Ordering Information
Part Number*
Standard Marking Code Pb-Free Marking Code** Voltage Junction Temp. Package
MIC5238-1.0BM5 L410 MIC5238-1.0YM5 L410 1.0V –40°C to +125°CSOT-23-5
MIC5238-1.1BM5 L411 MIC5238-1.1YM5 L411 1.1V –40°C to +125°CSOT-23-5
MIC5238-1.3BM5 L413 MIC5238-1.3YM5 L413 1.3V –40°C to +125°CSOT-23-5
MIC5238-1.0BD5 N410 MIC5238-1.0YD5 N410 1.0V –40°C to +125°CTSOT-23-5
MIC5238-1.1BD5 N411 MIC5238-1.1YD5 N411 1.1V –40°C to +125°CTSOT-23-5
MIC5238-1.3BD5 N413 MIC5238-1.3YD5 N413 1.3V –40°C to +125°CTSOT-23-5
*Other voltage options available. Contact Micrel Marketing for information.
**Under bar symbol (_) may not be to scale.
MIC5238 Micrel, Inc.
M9999-041205 2April 2005
Pin Configuration
IN
OUT
BIAS
EN
L4xx
13
45
2
GND
SOT-23-5 (M5)
Pin Description
SOT-23-5 Pin Name Pin Function
1INSupply Input
2GND Ground
3ENEnable (Input): Logic low = shutdown; logic high = enable. Do no leave
open.
4BIAS BiasSupply Input
5OUT Regulator Output
IN
OUT
BIAS
EN
N4xx
13
45
2
GND
TSOT-23-5 (D5)
April 2005 3 M9999-041205
MIC5238 Micrel, Inc.
Electrical Characteristics (Note 4)
TA = 25°C with VIN = VOUT + 1V; VBIAS = 3.3V; IOUT = 100µA; VEN = 2V, Bold values indicate –40°C<T
J<+125°C; unless otherwise specified.
Parameter Condition Min. Typ. Max. Units
Output Voltage Accuracy Variation from nominal VOUT –1.5 +1.5 %
–2 +2 %
Line Regulation VBIAS = 2.3V to 6V, Note 5 0.25 0.5 %
Input Line Regulation VIN = (VOUT + 1V) to 6V 0.04 %
Load Regulation Load = 100µA to 150mA 0.7 1 %
Dropout Voltage IOUT = 100µA50mV
IOUT = 50mA 230 300 mV
400 mV
IOUT = 100mA 270 mV
mV
IOUT = 150mA 310 450 mV
500 mV
BIAS Current, Note 6 IOUT = 100µA23µA
Input Current, Pin 1 IOUT = 100µA720 µA
IOUT = 50mA, Note 7 0.35 mA
IOUT = 100mA 1 mA
IOUT = 150mA 2 2.5 mA
Ground Current in Shutdown VEN ≤ 0.2V; VIN = 6V; VBIAS = 6V 1.5 5 µA
VEN = 0V; VIN = 6V; VBIAS = 6V 0.5 µA
Short Circuit Current VOUT = 0V 350 500 mA
Reverse Leakage VIN = 0V; VEN = 0V; VOUT = nom VOUT 5µA
Enable Input
Input Low Voltage Regulator OFF 0.2 V
Input High Voltage Regulator ON 2.0 V
Enable Input Current VEN = 0.2V; Regulator OFF –1.0 0.01 1.0 µA
VEN = 2.0V; Regulator ON 0.1 1.0 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. Human body model, 1.5k in series with 100pF.
Note 4. Specification for packaged product only.
Note 5. Line regulation measures a change in output voltage due to a change in the bias voltage.
Note 6. Current measured from bias input to ground.
Note 7. Current differential between output current and main input current at rated load current.
Absolute Maximum Ratings (Note 1)
Input Supply Voltage ........................................ –0.3V to 7V
BIAS Supply Voltage ........................................ –0.3V to 7V
Enable Input Voltage ........................................ –0.3V to 7V
Power Dissipation .................................... Internally Limited
Junction Temperature .............................. –40°C to +125°C
Storage Temperature ............................... –65°C to +150°C
ESD Rating, >1.5µA HBM, Note 3
Operating Ratings (Note 2)
Input Supply Voltage .......................................... 1.5V to 6V
BIAS Supply Voltage .......................................... 2.3V to 6V
Enable Input Voltage ............................................. 0V to 6V
Junction Temperature (TJ) ....................... –40°C to +125°C
Package Thermal Resistance
SOT-23-5 (θJA) .................................................. 235°C/W
MIC5238 Micrel, Inc.
M9999-041205 4April 2005
Typical Characteristics
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.2 1.7 2.2 2.7 3.2 3.7 4.2 4.7 5.2
OUTPUT VOLTAGE (V)
INPUT BIAS (V)
Output Voltage
vs. V
BIAS
100µA
150mA
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
1.1 1.21.3 1.41.5 1.61.7 1.81.9 2 2.1
OUTPUT VOLTAGE (V)
INPUT V
IN
(V)
Output Voltage
vs. VIN
100µA
150mA
0
50
100
150
200
250
300
350
400
0255075100 125 150
DROPOUT VOLTAGE (mV)
OUTPUT CURRENT (A)
Dropout Voltage
vs. Load
V
IN
= V
OUT
+ 1
0
200
400
600
800
1000
1200
1400
1600
1800
0255075100 125 150
GROUND CURRENT (µA)
OUTPUT CURRENT (mA)
Ground Current (V
IN
)
vs. Out
p
ut Current
V
IN
=V
OUT
+ 1
0
5
10
15
20
25
30
0255075100 125 150
GROUND CURRENT (µA)
OUTPUT CURRENT (mA)
Ground Current (V
BIAS
)
vs. Out
p
ut Current
V
IN
= V
OUT
+ 1
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
00.51.01.5 2.0
V
IN
GROUND CURRENT (mA)
V
IN
SUPPLY (V)
Ground Current (V
IN
)
vs. V
IN
Supply
1.1V
150mA
0
5
10
15
20
25
30
00.511.522.53
V
BIAS
GROUND CURRENT (µA)
INPUT VOLTAGE (V)
Ground Current (V
BIAS
)
vs. Input Voltage
I
LOAD
= 150mA
0
1
2
3
4
5
6
7
00.511.52
GROUND CURRENT (µA)
ENABLE (V)
Shutdown Current of
V
IN
No Load
0
2
4
6
8
10
12
14
16
18
20
00.511.52
GROUND CURRENT (mA)
ENABLE (V)
Shutdown Current of V
BIAS
No Load
0
5
10
15
20
25
30
00.511.52
GROUND CURRENT (mA)
ENABLE (V)
Shutdown Current
V
BIAS
+ V
IN
Tied
No Load
0
1
2
3
4
5
6
7
8
9
10
-40 -20 0 20 40 60 80 100 120
VIN GROUNF CURRENT (µA)
TEMPERATURE (°C)
Ground Current (V
IN
)
vs Tem
p
erature
1.1V
100µA
0
10
20
30
40
50
60
70
80
PSRR (dB)
FREQUENCY (Hz)
PSRR
150mA Load
C
OUT
= 2.2µF ceramic
V
IN
= 2.1V
V
OUT
= 1.1V
10 100 1k 10k 100k 1M 10M
April 2005 5 M9999-041205
MIC5238 Micrel, Inc.
0
5
10
15
20
25
30
35
40
-40 -20 0 20 40 60 80 100 120
VIN GROUND CURRENT (µA)
TEMPERATURE (°C)
V
BIAS
Ground Current
vs. Temperature
1.1V
150mA
0
5
10
15
20
25
30
35
40
-40 -20 0 20 40 60 80 100 120
V
IN
GROUND CURRENT (µA)
TEMPERATURE (°C)
V
BIAS
Ground Current
vs. Temperature
1.1V
75mA
1.0975
1.0980
1.0985
1.0990
1.0995
1.1000
1.1005
1.1010
1.1015
1.1020
1.1025
-40 -20 0 20 40 60 80 100 120
OUTPUT VOLTAGE (V)
TEMPERATURE (°C)
Output Voltage
vs. Tem
p
erature
1.1V
100µA
0
50
100
150
200
250
300
350
400
450
500
-40 -20 0 20 40 60 80 100 120
LOAD CURRENT (mA)
TEMPERATURE (°C)
Short Circuit Current
vs. Tem
p
erature
0
5
10
15
20
25
30
35
40
-40 -20 0 20 40 60 80 100 120
VIN GROUND CURRENT (µA)
TEMPERATURE (°C)
V
BIAS
Ground Current
vs. Temperature
1.1V
100µA
0
50
100
150
200
250
300
350
400
450
500
-40 -20 0 20 40 60 80 100 120
DROPOUT VOLTAGE (mV)
TEMPERATURE (°C)
Dropout Voltage
vs. Tem
p
erature
Load = 150mA
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
-40 -20 0 20 40 60 80 100 120
V
IN
GROUND CURRENT (mA)
TEMPERATURE (°C)
V
IN
Ground Current
vs. Tem
p
erature
1.1V
150mA
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
-40 -20 0 20 40 60 80 100 120
VIN GROUND CURRENT (mA)
TEMPERATURE (°C)
VIN Ground Current
vs. Tem
p
erature
1.1V
75mA
MIC5238 Micrel, Inc.
M9999-041205 6April 2005
Line Transient Response
TIME (200µs/div.)
OUTPUT VOLTAGE
(10mV/div.)
INPUT VOLTAGE
(1V/div.)
3.1V
2.1V
1.1V Output
C
OUT
= 4.7µF ceramic
Load Transient Response
TIME (400µs/div.)
OUTPUT CURRENT
(50mA/div.)
OUTPUT VOLTAGE
(200mV/div.)
1.1V output
C
OUT
= 4.7µF ceramic
150mA
1mA
EN Turn-On Characteristic
TIME (40µs/div.)
OUTPUT VOLTAGE
(500mA/div.)
ENABLE
(2V/div.)
Load Transient Response
TIME (400µs/div.)
OUTPUT CURRENT
(100mA/div.)
OUTPUT VOLTAGE
(200mV/div.)
V
IN
= 4V
V
OUT
= 3V
C
OUT
= 4.7µF ceramic
150mA
0mA
April 2005 7 M9999-041205
MIC5238 Micrel, Inc.
Functional Diagram
IN
EN
OUT
GND
BIAS
ENABLE
V
REF
Block Diagram – Fixed Output Voltage
MIC5238 Micrel, Inc.
M9999-041205 8April 2005
Applications Information
Enable/Shutdown
The MIC5238 comes with an active-high enable pin that
allows the regulator to be disabled. Forcing the enable pin low
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. Forcing the enable pin high enables the
output voltage.
Input Bias Capacitor
The input capacitor must be rated to sustain voltages that
may be used on the input. An input capacitor may be required
when the device is not near the source power supply or when
supplied by a battery. Small, surface mount, ceramic capaci-
tors can be used for bypassing. Larger values may be
required if the source supply has high ripple.
Output Capacitor
The MIC5238 requires an output capacitor for stability. The
design requires 2.2µF or greater on the output to maintain
stability. The design is optimized for use with low-ESR
ceramic chip capacitors. High ESR capacitors may cause
high frequency oscillation. The maximum recommended
ESR is 3Ω. The output capacitor can be increased without
limit. Larger valued capacitors help to improve transient
response.
X7R/X5R dielectric-type ceramic capacitors are recom-
mended because of their temperature performance. X7R-
type capacitors change capacitance by 15% over their oper-
ating temperature range and are the most stable type of
ceramic capacitors. Z5U and Y5V dielectric capacitors change
value by as much as 50% and 60% respectively over their
operating temperature ranges. To use a ceramic chip capaci-
tor with Y5V dielectric, the value must be much higher than a
X7R ceramic capacitor to ensure the same minimum capaci-
tance over the equivalent operating temperature range.
No-Load Stability
The MIC5238 will remain stable and in regulation with no load
unlike many other voltage regulators. This is especially
important in CMOS RAM keep-alive applications.
Thermal Considerations
The MIC5238 is designed to provide 150mA of continuous
current in a very small package. Maximum power dissipation
can be calculated based on the output current and the voltage
drop across the part. To determine the maximum power
dissipation of the package, use the junction-to-ambient ther-
mal resistance of the device and the following basic equation:
PTT
D(MAX)
J(MAX) A
JA
=−
θ
TJ(MAX) is the maximum junction temperature of the die,
125°C, and TA is the ambient operating temperature. θJA is
layout dependent; Table 1 shows the junction-to-ambient
thermal resistance for the MIC5238.
Package θθ
θθ
θJA Recommended
Minimum Footprint
SOT-23-5 235°C/W
Table 1. SOT-23-5 Thermal Resistance
The actual power dissipation of the regulator circuit can be
determined using the equation:
PD = (VIN – VOUT)IOUT + VINIGND
Substituting PD(MAX) for PD and solving for the operating
conditions that are critical to the application will give the
maximum operating conditions for the regulator circuit. For
example, when operating the MIC5238-1.0BM5 at 50°C with
a minimum footprint layout, the maximum input voltage for a
set output current can be determined as follows:
P125 C 50 C
235 C/W
D(MAX) =°−°
°
PD(MAX) = 319mW
The junction-to-ambient (θJA) thermal resistance for the
minimum footprint is 235°C/W, from Table 1. It is important
that the maximum power dissipation not be exceeded to
ensure proper operation. With very high input-to-output volt-
age differentials, the output current is limited by the total
power dissipation. Total power dissipation is calculated using
the following equation:
PD = (VIN – VOUT)IOUT + VIN x IGND + VBIAS x IBIAS
Since the bias supply draws only 18µA, that contribution can
be ignored for this calculation.
If we know the maximum load current, we can solve for the
maximum input voltage using the maximum power dissipa-
tion calculated for a 50°C ambient, 319mV.
PDMAX = (VIN – VOUT)IOUT + VIN x IGND
319mW = (VIN – 1V)150mA + VIN x 2.8mA
Ground pin current is estimated using the typical character-
istics of the device.
469mW = VIN (152.8mA)
VIN = 3.07V
For higher current outputs only a lower input voltage will work
for higher ambient temperatures.
Assuming a lower output current of 20mA, the maximum input
voltage can be recalculated:
319mW = (VIN – 1V)20mA + VIN x 0.2mA
339mW = VIN x 20.2mA
VIN = 16.8V
Maximum input voltage for a 20mA load current at 50°C
ambient temperature is 16.8V. Since the device has a 6V
rating, it will operate over the whole input range.
Dual Suppy Mode Efficiency
By utilizing a bias supply the conversion efficiency can be
greatly enhanced. This can be realized as the higher bias
supply will only consume a few µA’s while the input supply will
require a few mA’s! This equates to higher efficiency saving
valuable power in the system. As an example, consider an
output voltage of 1V with an input supply of 2.5V at a load
April 2005 9 M9999-041205
MIC5238 Micrel, Inc.
current of 150mA. The input ground current under these
conditions is 2mA, while the bias current is only 20µA. If we
calculate the conversion efficiency using the single supply
approach, it is as follows:
Input power = VIN × output current + VIN × (VBIAS ground
current + VIN ground current)
Input power = 2.5V × 150mA + 2.5 × (0.0002+0.002) =
380.5mW
Output power = 1V × 0.15 = 150mW
Efficiency = 150/380.5 × 100 = 39.4%
Now, using a lower input supply of 1.5V, and powering the
bias voltage only from the 2.5V input, the efficiency is as
follows:
Input power = VIN × output current + VIN × VIN ground current
+ VBIAS x VBIAS ground current
Input power = 1.5 × 150mA + 1.5 × 0.002 + 2.5 × 0.0002 =
225mW
Output power = 1V × 150mA = 150mW
Efficiency = 150/225 × 100 = 66.6 %
Therefore, by using the dual supply MIC5238 LDO the
efficiency is nearly doubled over the single supply version.
This is a valuable asset in portable power management
applications equating to longer battery life and less heat
being generated in the application.
This in turn will allow a smaller footprint design and an
extended operating life.
MIC5238 Micrel, Inc.
M9999-041205 10 April 2005
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)
1.90BSC
1.90BSC
1.90BSC
1.60BSC 1.60BSC
DIMENSIONS:
Millimeter
2.90BSC
0.10
0.01
0.20
0.12
0.30
0.50
0.30
0.45
0.90
0.80 2.9BSC 1.00
0.90
TSOT-23-5 (D5)
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
This 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.
© 2003 Micrel, Incorporated.
