MIC5255
150mA Low Noise µCap CMOS LDO
IttyBitty is a registered trademark of Micrel, Inc
MLF and MicroLeadFrame are registered trademarks of Amkor Technology, 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 M9999-110906
General Description
The MIC5255 is an efficient, precise CMOS voltage
regulator optimized for ultra-low-noise applications. It
offers 1% initial accuracy, extremely-low dropout voltage
(135mV at 150mA) and low ground current (typically
90µA). The MIC5255 provides a very-low-noise output,
ideal for RF applications where a clean voltage source is
required. A noise bypass pin is also available for further
reduction of output noise.
Designed specifically for handheld and battery-powered
devices, the MIC5255 provides a TTL-logic-compatible en-
able pin. When disabled, power consumption drops nearly
to zero.
The MIC5255 also works with low-ESR ceramic
capacitors, reducing the amount of board space necessary
for power applications, critical in handheld wireless
devices.
Key features include current limit, thermal shutdown, faster
transient response, and an active clamp to speed up
device turn-off. Available in the 6-pin 2mm × 2mm MLF
®
package, 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
MIC5255 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 SOT-23-5
• Ultra-low output noise: 30µV(rms)
• Stability with ceramic output capacitors
• Ultra-low dropout: 135mV @ 150mA
• High output accuracy:
– 1.0% initial accuracy
– 2.0% over temperature
• Low quiescent current: 90µA
• Tight load and line regulation
• TTL-Logic-controlled enable input
• “Zero” off-mode current
• Thermal shutdown and current limit protection
Applications
• Cellular phones and pagers
• Cellular accessories
• Battery-powered equipment
• Laptop, notebook, and palmtop computers
• Consumer/personal electronics
___________________________________________________________________________________________________________
Typical Application
C
OUT
= 1.0µF
C
IN
= 1.0µF
Ceramic
Ceramic
15
2
34
C
BYP
= 0.01µ
F
Enable
Shutdown
EN
V
OUT
MIC5255-x.x_M5
EN (pin 3) may be
connected directly
to IN (pin 1).
V
IN
Ultra-Low-Noise Regulator Application
Micrel, Inc. MIC5255
November 2006
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M9999-110906
Ordering Information
Part Number Marking
Standard Pb-Free Standard Pb-Free**
Voltage* Junction
Temp. Range Package
MIC5255-2.5BD5 MIC5255-2.5YD5 NW25 NW25 2.5V –40° to +125°C 5-Pin TSOT-23
MIC5255-2.5BM5 MIC5255-2.5YM5 LW25 KW25 2.5V –40° to +125°C 5-Pin SOT-23
MIC5255-2.6BD5 MIC5255-2.6YD5 NW26 NW26 2.6V –40° to +125°C 5-Pin TSOT-23
MIC5255-2.6BM5 MIC5255-2.6YM5 LW26 KW26 2.6V –40° to +125°C 5-Pin SOT-23
MIC5255-2.7BD5 MIC5255-2.7YD5 NW27 NW27 2.7V –40° to +125°C 5-Pin TSOT-23
MIC5255-2.7BM5 MIC5255-2.7YM5 LW27 KW27 2.7V –40° to +125°C 5-Pin SOT-23
MIC5255-2.75BM5 MIC5255-2.75YM5 LW2H KW2H 2.75V –40° to +125°C 5-Pin SOT-23
MIC5255-2.8BD5 MIC5255-2.8YD5 NW28 NW28 2.8V –40° to +125°C 5-Pin TSOT-23
MIC5255-2.8BM5 MIC5255-2.8YM5 LW28 KW28 2.8V –40° to +125°C 5-Pin SOT-23
MIC5255-2.8BML MIC5255-2.8YML W28 W28*** 2.8V –40° to +125°C 6-Pin 2x2 MLF
®
MIC5255-2.85BD5 MIC5255-2.85YD5 NW2J NW2J 2.85V –40° to +125°C 5-Pin TSOT-23
MIC5255-2.85BM5 MIC5255-2.85YM5 LW2J KW2J 2.85V –40° to +125°C 5-Pin SOT-23
MIC5255-2.85BML MIC5255-2.85YML W2J W2J*** 2.85V –40° to +125°C 6-Pin 2x2 MLF
®
MIC5255-2.9BD5 MIC5255-2.9YD5 NW29 NW29 2.9V –40° to +125°C 5-Pin TSOT-23
MIC5255-2.9BM5 MIC5255-2.9YM5 LW29 KW29 2.9V –40° to +125°C 5-Pin SOT-23
MIC5255-3.0BD5 MIC5255-3.0YD5 NW30 NW30 3.0V –40° to +125°C 5-Pin TSOT-23
MIC5255-3.0BM5 MIC5255-3.0YM5 LW30 KW30 3.0V –40° to +125°C 5-Pin SOT-23
MIC5255-3.0BML MIC5255-3.0YML W30 W30*** 3.0V –40° to +125°C 6-Pin 2x2 MLF
®
MIC5255-3.1BM5 MIC5255-3.1YM5 LW31 KW31 3.1V –40° to +125°C 5-Pin SOT-23
MIC5255-3.2BM5 MIC5255-3.2YM5 LW32 KW32 3.2V –40° to +125°C 5-Pin SOT-23
MIC5255-3.3BD5 MIC5255-3.3YD5 NW33 NW33 3.3V –40° to +125°C 5-Pin TSOT-23
MIC5255-3.3BM5 MIC5255-3.3YM5 LW33 KW33 3.3V –40° to +125°C 5-Pin SOT-23
MIC5255-3.3BML MIC5255-3.3YML W33 W33*** 3.3V –40° to +125°C 6-Pin 2x2 MLF
®
MIC5255-3.5BM5 MIC5255-3.5YM5 LW35 KW35 3.5V –40° to +125°C 5-Pin SOT-23
Notes:
* Other Voltage available. Contact Micrel for details.
** Under bar / Over bar symbol may not be to scale.
*** Over bar symbol located after Pin 1 identifier.
Micrel, Inc. MIC5255
November 2006
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Pin Configur ation
IN
OUT
BYP
EN
LWxx
13
45
2
GND
IN
OUT
BYP
EN
NWxx
13
45
2
GND
1EN
GND
IN
6 BYP
NC
OUT
5
4
2
3
Wxx
MIC5255-x.xBM5
5-Pin SOT23 (M5) MIC5255-x.xBD5
5-Pin Thin SOT23 (D5) MIC5255-x.xBML
6-Pin 2x2 MLF
®
(ML)
IN
OUT
BYP
EN
KWxx
13
45
2
GND
IN
OUT
BYP
EN
NWxx
13
45
2
GND
1EN
GND
IN
6 BYP
NC
OUT
5
4
2
3
Wxx
MIC5255-x.xYM5
5-Pin SOT23 (M5) MIC5255-x.xYD5
5-Pin Thin SOT23 (D5) MIC5255-x.xYML
6-Pin 2x2 MLF
®
(ML)
Pin Description
Pin Number
SOT23-5
TSOT23-5
Pin Number
6-MLF
Pin Name Pin Name
1 3 IN Supply Input.
2 2 GND Ground.
3 1 EN
Enable/Shutdown (Input): CMOS compatible input. Logic high = enable;
logic low = shutdown. Do not leave open.
4 6 BYP
Reference Bypass: Connect external 0.01µF CBYP 1.0µF capacitor
to GND to reduce output noise. May be left open.
5 4 OUT Regulator Output.
– 5 NC No internal connection.
– EP GND
Ground: Internally connected to the exposed pad. Connect externally to
GND pin.
Micrel, Inc. MIC5255
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
2x2 MLF-6 (
θ
JA
) .................................................90°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, C
OUT
= 1.0µF, C
BYP
= 0.01µF 60 dB
f = 100Hz, V
IN
= V
OUT
+1 60 dB
PSRR Ripple Rejection
f = 10kHz, V
IN
= V
OUT
+1 50 dB
I
LIM
Current Limit V
OUT
= 0V 160 425 mV
e
n
Output Voltage Noise C
OUT
= 1.0µF, C
BYP
= 0.01µF,
f = 10Hz to 100kHz
30 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
Thermal Protection
Thermal Shutdown Temperature 150 °C
Thermal Shutdown Hysteresis 10 °C
Micrel, Inc. MIC5255
November 2006
5
M9999-110906
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. Human body model, 1.5k in series with 100pF.
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 1.0mA 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 1V
differential. 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.
Micrel, Inc. MIC5255
November 2006
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Typical Characteristics
Micrel, Inc. MIC5255
November 2006
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Typical Characteristics
Micrel, Inc. MIC5255
November 2006
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Functional Characteristics
Micrel, Inc. MIC5255
November 2006
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Functional Diagram
Micrel, Inc. MIC5255
November 2006
10
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Application Information
Enable/Shutdown
The MIC5255 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 MIC5255 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
performance 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 MIC5255 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
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 an X7R
ceramic capacitor to ensure the same minimum
capacitance over the equivalent operating temperature
range.
Bypass Capacitor
A capacitor can be placed from the noise bypass pin to
ground to reduce output voltage noise. The capacitor
bypasses the internal reference. A 0.01µF capacitor is
recommended for applications that require low-noise
outputs. The bypass capacitor can be increased, further
reducing noise and improving PSRR. Turn-on time
increases slightly with respect to bypass capacitance. A
unique quick-start circuit allows the MIC5255 to drive a
large capacitor on the bypass pin without significantly
slowing turn-on time. Refer to the “
Typical Character-
istics
” section for performance with different bypass
capacitors.
Active Shutdown
The MIC5255 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 MIC5255 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 MIC5255 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 MIC5255.
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 MIC5255-3.0BM5 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
Micrel, Inc. MIC5255
November 2006
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M9999-110906
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 “
Reg-
ulator Thermals
” section of Micrel’s Designing with Low-
Dropout Voltage Regulators handbook.
Micrel, Inc. MIC5255
November 2006
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Package Information
5-Pin SOT (M5)
5-Pin Thin SOT (D5)
Micrel, Inc. MIC5255
November 2006
13
M9999-110906
6-Pin MLF
®
(ML)
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.
© 2004 Micrel, Incorporated.
