MIC5238
Ultra-Low Quiescent Current, 150mA
µCap LDO Regulator
IttyBitty is a registered trademark of Micrel, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
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.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
Ultra-low input voltage range:1.5V to 6V
Ultra-low output voltage:1.0V 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
Ultra-Low Voltage Application
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Ordering Information
Part Number
Standard Marking Code Pb-Free Marking Code*
Voltage** Junction
Temp. Range Package
MIC5238-1.0BM5 L410 MIC5238-1.0YM5 L410 1.0V –40° to +125°C SOT-23-5
MIC5238-1.1BM5 L411 MIC5238-1.1YM5 L411 1.1V –40° to +125°C SOT-23-5
MIC5238-1.3BM5 L413 MIC5238-1.3YM5 L413 1.3V –40° to +125°C SOT-23-5
MIC5238-1.0BD5 N410 MIC5238-1.0YD5 N410 1.0V –40° to +125°C TSOT-23-5
MIC5238-1.1BD5 N411 MIC5238-1.1YD5 N411 1.1V –40° to +125°C TSOT-23-5
MIC5238-1.3BD5 N413 MIC5238-1.3YD5 N413 1.3V –40° to +125°C TSOT-23-5
Notes:
* Under bar symbol ( _ ) may not be to scale.
** Other voltage options available. Contact Micrel Marketing for details.
Pin Configur ation
5-Pin SOT-23 (M5) 5-Pin Thin SOT-23 (D5)
Pin Description
Pin Number Pin Name Pin Function
1 IN Supply Input
2 GND Ground
3 EN
Enable (Input): Logic Low = shutdown; Logic High = enable. Don not leave
open.
4 BIAS Bias Supply Input
5 OUT Regulator Output
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Absolute Maximum Ratings(1)
Input Supply Voltage (VIN)................................. –0.3V to 7V
BIAS Supply Voltage (VBIAS).............................. –0.3V to 7V
Enable Supply Voltage (VEN)............................. –0.3V to 7V
Power Dissipation (PD)..............................Internally Limited
Junction Temperature (TJ) ........................–40°C to +125°C
Storage Temperature (TS).........................–65°C to +150°C
ESD Rating(3)......................................................1.5µA HBM
Operating Ratings(2)
Supply Voltage (VIN)............................................ 1.5V to 6V
BIAS Supply Voltage (VBIAS)................................ 2.3V to 6V
Enable Supply Voltage (VEN).................................. 0V to 6V
Junction Temperature (TJ) ........................–40°C to +125°C
Package Thermal Resistance
SOT-23-5 (θJA) .................................................235°C/W
Electrical Characteristics(4)
TA = 25°C with VIN = VOUT + 1V; VBIAS = 3.3V; IOUT = 100µA; VEN = 2V, bold values indicate –40°C < TJ < +125°C, unless
specified.
Parameter Condition Min Typ Max Units
Output Voltage Accuracy Variation from nominal VOUT –1.5
–2
+1.5
+2
%
%
Line Regulation VBIAS = 2.3V to 6V, Note 5 0.25 0.5 %
Input Line Regulation VIN = (VOUT 1V) to 6V 0.04 4 %
Load Regulation Load = 100µA to 150mA 0.7 1 %
IOUT = 100µA 50 mV
IOUT = 50mA 230 300
400
mV
mV
IOUT = 100mA 270 mV
Dropout Voltage
IOUT = 150mA 310 450
500
mV
mV
BIAS Current, Note 6 IOUT = 100µA 23 µA
IOUT = 100µA 7 20 µA
IOUT = 50mA, Note 7 0.35 mA
IOUT = 100mA 1 mA
Input Current, Pin 1
IOUT = 150mA 2 2.5 mA
VEN 0.2V, VIN = 6V, VBIAS = 6V 1.5 5 µA Ground Current in Shutdown
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 5 µA
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Electrical Characteristics(4) cont.
TA = 25°C with VIN = VOUT + 1V; VBIAS = 3.3V; IOUT = 100µA; VEN = 2V, bold values indicate –40°C < TJ < +125°C, unless
specified.
Parameter Condition Min Typ Max Units
Enable Input
Input Low Voltage Regulator OFF 0.2
V
Input High Voltage Regulator ON 2.0 V
VEN = 0.2V, Regulator OFF –1.0 0.01 1.0 µA Enable Input Current
VEN = 0.2V, Regulator ON 0.1 1.0 µA
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. Human body model, 1.5k in series with 100pF.
4. Specification for packaged product only.
5. Line regulation measures a change in output voltage due to a change in the bias voltage.
6. Current measured from bias input to ground.
7. Current differential between output current and main input current at rated load current.
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Typical Characteristics
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Typical Characteristics cont .
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Functional Characteristics
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Functional Diagram
Block Diagram – Fixed Ou tput Voltage
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Application 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 capacitors 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 3. 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
operating 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 capacitor with Y5V dielectric, the value must be much
higher than a X7R ceramic capacitor to ensure the same
minimum capacitance 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 thermal resistance of the device and
the following basic equation:
JA
AJ(max)
D(MAX)
T - T
P
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 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:
P
D = (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.
C/W235
C50 - C125
PD(MAX) °
°°
=
P
D(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
voltage differentials, the output current is limited by the total
power dissipation. Total power dissipation is calculated
using the following equation:
P
D = (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.
P
D(MAX) = (VIN – VOUT) IOUT + VIN x IGND
319mW = (VIN – 1V) 150mA + VIN x 2.8mA
Ground pin current is estimated using the typical
characteristics of the device.
469mW = VIN (152.8mA)
V
IN = 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
V
IN = 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.
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Dual Supply 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 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.
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Package Information
5-Pin SOT-23 (M5)
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Package Information cont.
5-Pin Thin SOT-23 (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
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
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical impla
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can nt
© 2003 Micrel, Incorporated.