MIC5256
150mA µCap LDO with Error Flag
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
November 2006
1 M9999-111606
General Description
The MIC5256 is an efficient, precise CMOS voltage
regulator. It offers better than 1% initial accuracy,
extremely low-dropout voltage (typically 135mV at 150mA)
and low ground current (typically 90µA) over load. The
MIC5256 features an error flag that indicates an output
fault condition such as overcurrent, thermal shutdown and
dropout.
Designed specifically for handheld and battery-powered
devices, the MIC5256 provides a TTL-logic-compatible
enable pin. When disabled, power consumption drops
nearly to zero.
The MIC5256 also works with low-ESR ceramic
capacitors, reducing the amount of board space necessary
for power applications, critical in hand-held wireless
devices.
Key features include current limit, thermal shutdown, faster
transient response, and an active clamp to speed up
device turnoff. Available in the IttyBitty
®
SOT-23-5
package and the new Thin SOT-23-5, which offers the
same footprint as the standard IttyBitty
®
SOT-23-5, but
only 1mm tall. The MIC5256 offers a range of output
voltages.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Features
• Input voltage range: 2.7V to 6.0V
• Thin SOT package: 1mm height
• Error flag indicates fault condition
• Stable with ceramic output capacitor
• Ultralow dropout: 135mV @ 150mA
• High output accuracy:
– 1.0% initial accuracy
– 2.0% over temperature
• Low quiescent current:90µA
• Tight load and line regulation
• Thermal shutdown and current limit protection
• “Zero” off-mode current
• TTL logic-controlled enable input
Applications
• Cellular phones and pagers
• Cellular accessories
• Battery-powered equipment
• Laptop, notebook, and palmtop computers
• Consumer/personal electronics
___________________________________________________________________________________________________________
Typical Application
Low-Noise Regulator Application
Micrel, Inc. MIC5256
November 2006
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Ordering Information
Part Number Marking
Standard Pb-Free Standard Pb-Free*
Voltage** Junction
Temp. Range Package
MIC5256-2.5BM5 MIC5256-2.5YM5 LX25 LX25 2.5V –40° to +125°C 5-Pin SOT23
MIC5256-2.6BM5 MIC5256-2.6YM5 LX26 LX26 2.6V –40° to +125°C 5-Pin SOT23
MIC5256-2.7BM5 MIC5256-2.7YM5 LX27 LX27 2.7V –40° to +125°C 5-Pin SOT23
MIC5256-2.8BM5 MIC5256-2.8YM5 LX28 LX28 2.8V –40° to +125°C 5-Pin SOT23
MIC5256-2.85BM5 MIC5256-2.85YM5 LX2J LX2J 2.85V –40° to +125°C 5-Pin SOT23
MIC5256-2.9BM5 MIC5256-2.9YM5 LX29 LX29 2.9V –40° to +125°C 5-Pin SOT23
MIC5256-3.0BM5 MIC5256-3.0YM5 LX30 LX30 3.0V –40° to +125°C 5-Pin SOT23
MIC5256-3.1BM5 MIC5256-3.1YM5 LX31 LX31 3.1V –40° to +125°C 5-Pin SOT23
MIC5256-3.3BM5 MIC5256-3.3YM5 LX33 LX33 3.3V –40° to +125°C 5-Pin SOT23
MIC5256-2.85BD5 MIC5256-2.85YD5 NX2J NX2J 2.85V –40° to +125°C 5-Pin TSOT23
Notes:
* Under bar symbol ( _ ) may not be to scale.
** Other Voltage available. Contact Micrel for details.
Pin Configur ation
MIC5256-x.xBM5
5-Pin SOT23 MIC5256-x.xBD5
5-Pin Thin SOT23
MIC5256-x.xYM5
5-Pin SOT23 MIC5256-x.xYD5
5-Pin Thin SOT23
Pin Description
Pin Number Pin Name Pin Name
1 IN Supply Input.
2 GND Ground.
3 EN
Enable/Shutdown (Input): CMOS compatible input. Logic high = enable;
logic low = shutdown. Do not leave open.
4 FLG
Error Flag (Output): Open-drain output. Active low indicates an output
undervoltage condition.
5 OUT Regulator Output.
Micrel, Inc. MIC5256
November 2006
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Absolute Maximum Ratings(1)
Supply Voltage (V
IN
)............................................. 0V to +7V
Enable Voltage (V
EN
)............................................ 0V to +7V
Power Dissipation (P
D
) ........................... Internally Limited
(3)
Junction Temperature (T
J
) ........................–40°C to +125°C
Storage Temperature (T
s
) .........................–60°C to +150°C
Lead Temperature (soldering, 5 sec.)........................ 260°C
EDS Rating
(4)
.................................................................. 2kV
Operating Ratings(2)
Supply Voltage (V
IN
)........................................ +2.7V to +6V
Enable Voltage (V
EN
).............................................. 0V to V
IN
Junction Temperature (T
J
) ........................–40°C to +125°C
Thermal Resistance
SOT23-5 (θ
JA
) ..................................................235°C/W
Electrical Characteristics(5)
V
IN
= V
OUT
+ 1V, V
EN
= V
IN
; I
OUT
= 100µA; T
J
= 25°C, bold values indicate –40°C T
J
+125°C; unless noted.
Symbol Parameter Condition Min Typ Max Units
V
O
Output Voltage Accuracy I
OUT
= 100µA –1
–2
1
2
%
%
V
LNR
Line Regulation V
IN
= V
OUT
+ 1V to 6V 0.02 0.05 %/V
V
LDR
Load Regulation I
OUT
= 0.1mA to 150mA
(6)
1.5 2.5 %
I
OUT
= 100µA 0.1 5 mV
I
OUT
= 100mA 90 150 mV
V
IN
– V
OUT
Dropout Voltage
(7)
I
OUT
= 150mA 135 200
250
mV
mV
I
Q
Quiescent Current V
EN
0.4V (shutdown) 0.2 1 µA
I
OUT
= 0mA 90 150 µA I
GND
Ground Pin Current
(8)
I
OUT
= 150mA 117 µA
f = 10Hz, V
IN
= V
OUT
+ 1V; C
OUT
= 1.0µF 60 dB
f = 100Hz, V
IN
= V
OUT
+ 0.5V; C
OUT
= 1.0µF 60 dB
PSRR Ripple Rejection
f = 10kHz, V
IN
= V
OUT
+ 0.5V 45 dB
I
LIM
Current Limit V
OUT
= 0V 160 425 mV
e
n
Output Voltage Noise tbd µV(rms)
Enable Input
V
IL
Enable Input Logic-Low Voltage V
IN
= 2.7V to 5.5V, regulator shutdown 0.4 V
V
IH
Enable Input Logic-High Voltage V
IN
= 2.7V to 5.5V, regulator enabled 1.6 V
V
IL
0.4V, regulator shutdown 0.01 µA I
EN
Enable Input Current
V
IH
1.6V, regulator enabled 0.01 µA
Shutdown Resistance Discharge 500
Error Flag
V
FLG
Low Threshold
High Threshold
% of V
OUT
(Flag ON)
% of V
OUT
(Flag OFF)
90
96
%
%
V
OL
Output Logic-Low Voltage I
L
= 100µA, fault condition 0.02 0.1 V
I
FL
Flag Leakage Current flag off, V
FLG
= 6V 0.01 µA
Thermal Protection
Thermal Shutdown Temperature 150 °C
Thermal Shutdown Hysteresis 10 °C
Micrel, Inc. MIC5256
November 2006
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Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. The maximum allowable power dissipation of any T
A
(ambient temperature) is P
D(max)
= T
J(max)
–T
A
/
JA
. Exceeding the maximum allowable power
dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. The
JA
of the MIC5255-x.xBM5 (all versions) is
235°C/W on a PC board (see “Thermal Considerations” section for further details).
4. Devices are ESD sensitive. Handling precautions recommended.
5. Specification for packaged product only.
6. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are tested for load regulation in the load range from
0.1mA to 150mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification.
7. Dropout Voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured at 1Vdifferential.
For outputs below 2.7V, dropout voltage is the input-to-output voltage differential with the minimum input voltage 2.7V. Minimum input operating
voltage is 2.7V.
8. Ground pin current is the regulator quiescent current. The total current drawn from the supply is the sum of the load current plus the ground pin
current.
Test Circuit
Micrel, Inc. MIC5256
November 2006
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Typical Characteristics
100
105
110
115
120
125
130
0.1 1 10 100 1000
(TNERRUCDNUORGµ)A
OUTPUT CURRENT (mA)
Ground Pin Current
V
IN
= V
OUT
+ 1V
0
20
40
60
80
100
120
140
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
(TNERRUCDNUORGµ)A
INPUT VOLTAGE (V)
Ground Pin Current
I
LOAD
= 150mA
0
0.5
1
1.5
2
2.5
3
3.5
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
)V(EGATLOVTUPTUO
INPUT VOLTAGE (V)
Dropout Characteristics
I
LOAD
= 150mA
I
LOAD
= 100µA
0
20
40
60
80
100
120
140
160
180
-40 -20 0 20 40 60 80 100120140
)Vm(EGATLOVTUOPORD
TEMPERATURE (°C)
Dropout Voltage
I
LOAD
= 150mA
0
20
40
60
80
100
120
140
160
180
0 20 40 60 80 100 120 140 160
)Vm(EGATLOVTUOPORD
OUTPUT CURRENT (mA)
Dropout Voltage
T = –40C
T = 25C T = 125C
Micrel, Inc. MIC5256
November 2006
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Typical Characteristics (cont.)
0
100
200
300
400
500
600
3 3.5 4 4.5 5 5.5 6
)Am(TNERRUCTIUCRICTROHS
INPUT VOLTAGE (V)
Short Circuit Current
Micrel, Inc. MIC5256
November 2006
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Functional Characteristics
Micrel, Inc. MIC5256
November 2006
8 M9999-111606
Functional Diagram
Micrel, Inc. MIC5256
November 2006
9 M9999-111606
Application Information
Enable/Shutdown
The MIC5256 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. This part is CMOS
and the enable pin cannot be left floating; a floating
enable pin may cause an indeterminate state on the
output.
Input Capacitor
The MIC5256 is a high performance, high bandwidth
device. Therefore, it requires a well-bypassed input
supply for optimal performance. A 1µF capacitor is
required from the input to ground to provide stability.
Low ESR ceramic capacitors provide optimal perform-
ance at a minimum of space. Additional high-frequency
capacitors, such as small valued NPO dielectric type
capacitors, help filter out high frequency noise and are
good practice in any RF based circuit.
Output capacitor
The MIC5256 requires an output capacitor for stability.
The design requires 1µF 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 300m. The output capacitor can
be increased, but performance has been optimized for a
1µF ceramic output capacitor and does not improve
significantly with larger capacitance.
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 dielec-
tric 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 an X7R
ceramic capacitor to ensure the same minimum capaci-
tance over the equivalent operating temperature range.
Error Flag
The error flag output is an active-low, open-drain output
that drives low when a fault condition AND an under-
voltage detection occurs. Internal circuitry intelligently
monitors overcurrent, overtemperature and dropout
conditions and ORs these outputs together to indicate
some fault condition. The output of that OR gate is
ANDed with an output voltage monitor that detects an
undervoltage condition. That output drives the open-
drain transistor to indicate a fault. This prevents chat-
tering or inadvertent triggering of the error flag. The error
flag must be pulled-up using a resistor from the flag pin
to either the input or the output.
The error flag circuit was designed essentially to work
with a capacitor to ground to act as a power-on reset
generator, signaling a power-good situation once the
regulated voltage was up and/or out of a fault condition.
This capacitor delays the error signal from pulling high,
allowing the down stream circuits time to stabilize. When
the error flag is pulled-up to the input without using a
pull-down capacitor, then there can be a glitch on the
error flag upon start up of the device. This is due to the
response time of the error flag circuit as the device starts
up. When the device comes out of the “zero” off mode
current state, all the various nodes of the circuit power
up before the device begins supplying full current to the
output capacitor. The error flag drives low immediately
and then releases after a few microseconds. The
intelligent circuit that triggers an error detects the output
going into current limit AND the output being low while
charging the output capacitor. The error output then pulls
low for the duration of the turn-on time. A capacitor from
the error flag to ground will filter out this glitch. The glitch
does not occur if the error flag pulled up to the output.
Active Shutdown
The MIC5256 also features an active shutdown clamp,
which is an N-channel MOSFET that turns on when the
device is disabled. This allows the output capacitor and
load to discharge, de-energizing the load.
No Load Stability
The MIC5256 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 MIC5256 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)
TT
P
T
J(max)
is the maximum junction temperature of the die,
125°C, and T
A
is the ambient operating temperature.
JA
is layout dependent; Table 1 shows examples of
junction-to-ambient thermal resistance for the MIC5256.
Micrel, Inc. MIC5256
November 2006
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Package θ
JA
Recommended
Minimum Footprint θ
JA
1” Square
Copper Clad θ
JC
SOT23-5
(M5 or D5)
235°C/W 185°C/W 145°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
= (V
IN
– V
OUT
) I
OUT
+ V
IN
I
GND
Substituting P
D(max)
for P
D
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 MIC5256-3.0BM5 at
50°C with a minimum footprint layout, the maximum
input voltage for a set output current can be determined
as follows:
⎟
⎠
⎞
⎜
⎝
⎛
°
°−°
=C/W235
C50C125
P
D(max)
P
D(max)
= 315mW
The junction-to-ambient thermal resistance for the
minimum footprint is 235°C/W, from Table 1. The
maximum power dissipation must not be exceeded for
proper operation. Using the output voltage of 3.0V and
an output current of 150mA, the maximum input voltage
can be determined. Because this device is CMOS and
the ground current is typically 100µA over the load
range, the power dissipation contributed by the ground
current is < 1% and can be ignored for this calculation.
315mW = (V
IN
– 3.0V) 150mA
315mW = V
IN
·•150mA – 450mW
810mW = V
IN
·•150mA
V
IN(max)
= 5.4V
Therefore, a 3.0V application at 150mA of output current
can accept a maximum input voltage of 5.4V in a SOT-
23-5 package. For a full discussion of heat sinking and
thermal effects on voltage regulators, refer to the
Regulator Thermals section of Micrel’s Designing with
Low-Dropout Voltage Regulators handbook.
Fixed Regulator Applications
Figure 1. Low-Noise Fixed Voltage Application
Figure 1 shows a standard low-noise configuration with a
47k pull-up resistor from the error flag to the input
voltage and a pull-down capacitor to ground for the
purpose of fault indication. EN (Pin 3) is connected to IN
(Pin 1) for an application where enable/shutdown is not
required. C
OUT
=1.0µF minimum.
Micrel, Inc. MIC5256
November 2006
11 M9999-111606
Package Information
5-Pin SOT (M5)
5-Pin Thin SOT (D5)
Micrel, Inc. MIC5256
November 2006
12 M9999-111606
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.
© 2003 Micrel, Incorporated.
