MIC5268
150mA µCap CMOS LDO Regulator
w/Power Good
IttyBitty is a 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
September 2006 1 M9999-91506
General Description
The MIC5268 is an efficient, precise CMOS voltage
regulator with power good output. The MIC5268 offers
better than 3% initial accuracy, and constant ground
current (typically 100µA) over load.
The MIC5268 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, a
push-pull output for faster transient response, and an
active clamp to speed up device turnoff. Available in the
IttyBitty™ SOT-23-5 package, the MIC5268 is a fixed 1.2V
regulator.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Features
• Power Good indicator
• Load independent, ultra-low ground current: 100µA
• 150mA output current
• Current limiting
• Thermal shutdown
• Tight load and line regulation
• “Zero” off-mode current
• Stability with low-ESR capacitors
• Fast transient response
• TTL-Logic-controlled enable input
Applications
• Processor power-up sequencing
• Laptop, notebook, and palmtop computers
• PCMCIA V
CC
and V
PP
regulation/switching
Ordering Information
Part Number Marking
Standard Pb-Free Standard Pb-Free
Voltage Junction
Temp. Range
(1)
Package
MIC5268-1.2BM5 MIC5268-1.2YM5 L512 L512 1.2V –40° to +125°C 5-Pin SOT-23
Note:
1. Other Voltage available. Contact Micrel Marketing for details.
Typical Application
15
2
34
C
47k
OU
T
Enable
Shutdown
EN
V
OUT
MIC5268-x.xBM5/YM5
V
IN
PG
1.2V Regulator with Power Good
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Pin Configur ation
MIC5268-x.x-BM5/YM5
5-Pin SOT-23 (M5)
Pin Description
Pin Number Pin Name Pin Function
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 PG Power Good Output
5 OUT Regulator Output
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September 2006 3 M9999-091506
Absolute Maximum Ratings(1)
Supply Input Voltage (V
IN
).................................... 0V to +7V
Enable Input Voltage (V
EN
)..................................... 0V to V
IN
Flag Output Voltage (V
PG
) ...................................... 0V to V
IN
Junction Temperature (T
J
) ....................................... +150°C
Lead Temperature (soldering, 5sec.)......................... 260°C
Storage Temperature (T
s
) .........................–65°C to +150°C
EDS Rating
(3)
Operating Ratings(2)
Supply voltage (V
IN
) ........................................ +2.7V to +6V
Enable Input Voltage (V
EN
)..................................... 0V to V
IN
Flag Output Voltage (V
PG
)...................................... 0V to V
IN
Junction Temperature (T
J
) ........................–40°C to +125°C
Thermal Resistance
SOT-23 (θ
JA
)....................................................235°C/W
Electrical Characteristics
V
IN
= xx; R
L
=xx; T
A
= 25°C, bold values indicate –40°C< T
A
< +85°C, unless noted.
Symbol Parameter Condition Min Typ Max Units
V
O
Output Voltage Accuracy I
OUT
= 100µA –3
–4
3
4
%
%
∆V
LNR
Line Regulation V
IN
= 2.7V to 6V –0.3 0.3 %/V
∆V
LNR
Load Regulation I
OUT
= 0.1mA to 150mA, Note 4 3 5 %
I
Q
Quiescent Current V
EN
≤ 0.4V (shutdown) PG = NC 0.45 1 µA
I
OUT
= 0mA; V
IN
= 6.0V 110 150 µA I
GND
Ground Pin Current, Note 5
I
OUT
= 150mA; V
IN
= 6.0V 110 150 µA
I
LIM
Current Limit V
OUT
= 0V 160 350 mA
Enable Input
V
IL
Enable Input Logic-Low Voltage V
IN
= 5.5V, regulator shutdown 0.4 V
V
IH
Enable Input Logic-High Voltage V
IN
= 5.5V, regulator enabled 1.6 V
V
IL
≤ 0.4V; V
IN
= 5.5V 0.01 µA I
EN
Enable Input Current
V
IH
≥ 1.6V; V
IN
= 5.5V 0.01 µA
Thermal Protection
Thermal Shutdown Temperature 150 °C
Thermal Shutdown Hysteresis 10 °C
Power Good, Note 6
V
PG
Low Threshold
High Threshold
% of V
OUT
(PG ON)
% of V
OUT
(PG OFF)
88
97
%
%
V
OL
PG Output Logic-Low Voltage I
L
= 10mA 250 500 mV
I
PG
Power Good Leakage Current power good off, V
PG
= 5.5V 0.01 µA
V
PG
Delay Delay time to Power Good See Timing Diagram 1 5 ms
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.
4. 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.
5. 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.
6. The power good is a function of the output voltage being 5% low and the detection of one of the following: overcurrent, overtemperature or dropout.
See “Applications Information” section for additional information.
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September 2006 4 M9999-091506
Typical Characteristics
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Block Diagram
Reference
Voltage
EN
Quickstart
Under-
voltage
Lockout
Thermal
Sensor
IN
FAULT
GND
ACTIVE SHUTDOWN
PULL
UP
PULL
DOWN
Overcurrent
Dropout
Detection
Out of
Regulation
Detection
PG
OUT
Current
Amplifier
Startup/
Shutdown
Control
Error
Amplifier
Delay
Timing Diagram
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September 2006 6 M9999-091506
Application Information
Enable/Shutdown
The MIC5268 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
An input capacitor is not required for stability. A 1µF
input capacitor is recommended when the bulk ac supply
capacitance is more than 10 inches away from the
device, or when the supply is a battery.
Output Capacitor
The MIC5268 requires an output capacitor for stability.
The design requires 1µF or greater on the output to
maintain stability. The capacitor can be a low-ESR
ceramic chip capacitor. The MIC5268 has been
designed to work specifically with the low-cost, small
chip capacitors. Tantalum capacitors can also be used
for improved capacitance overtemperature. The value of
the capacitor can be increased without bound.
X7R dielectric ceramic capacitors are recommended
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 50% and 60%
respectively over their operating temperature ranges. To
use a ceramic chip capacitor withY5V dielectric, the
value must be much higher than an X7Rceramic or a
tantalum capacitor to ensure the same minimum
capacitance value over the operating temperature range.
Tantalum capacitors have a very stable dielectric (10%
over their operating temperature range) and can also be
used with this device.
Power Good
The power good output is an open-drain output. It is
designed essentially to work as a power-on reset
generator once the regulated voltage was up and/or a
fault condition. The output of the power good drives low
when a fault condition AND an undervoltage detection
occurs. The power good output comes back up once the
output has reached 97% of its nominal value and a 1ms
to 5ms delay has passed. See Timing Diagram.
The MIC5268’s internal circuit intelligently monitors
overcurrent, overtemperature and dropout conditions
and ORs these outputs together indicate some fault
condition. This output is fed into an on-board delay
circuitry that drives the open drain transistor to indicate a
fault.
Transient Response
The MIC5268 implements a unique output stage to
dramatically improve transient response recovery time.
The output is a totem-pole configuration with a P-
channel MOSFET pass device and an N-channel
MOSFET clamp. The N-channel clamp is a significantly
smaller device that prevents the output voltage from
overshooting when a heavy load is removed. This
feature helps to speed up the transient response by
significantly decreasing transient response recovery time
during the transition from heavy load (100mA) to light
load (100µA).
Active Shutdown
The MIC5268 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.
Thermal Considerations
The MIC5268 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) θ
TT
P
T
J(max)
is the maximum junction temperature of the die,
125°C, and T
A
is the ambient operating temperature. θ
JA
is layout dependent; Table 1 shows examples of
junction-to-ambient thermal resistance for the MIC5268.
Package θ
JA
Recommended
Minimum Footprint θ
JA
1” Square
Copper Clad θ
JC
SOT-23-5 (M5) 235°C/W 185°C/W 145°C/W
Table 1. 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 MIC5268-1.2BM5 at
50°C with a minimum footprint layout, the maximum
input voltage for a set output current can be determined
as follows:
⎟
⎠
⎞
⎜
⎝
⎛
°
°−°
=C235
C50C125
P
D(max)
P
D(max)
= 315mW
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September 2006 7 M9999-091506
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 1.2V 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
– 1.2V) 150mA
315mW = V
IN
·150mA – 195mW
510mW = V
IN
·150mA
V
IN
(max) = 3.4V
Therefore, a 1.2V application at 150mA of output current
can accept a maximum input voltage of 3.4V 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.
Dual-Supply Operation
When used in dual supply systems where the regulator
load is returned to a negative supply, the output voltage
must be diode clamped to ground.
Micrel, Inc. MIC5268
September 2006 8 M9999-091506
Package Information
5-Pin SOT-23 (M5)
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.
© 2002 Micrel, Incorporated.
