MIC5247 Micrel, Inc.
February 2006 1 M9999-022406
General Description
The MIC5247 is an efficient and precise, low-voltage CMOS
voltage regulator optimized for ultra-low noise applications.
The MIC5247 offers better than 1% initial accuracy and
85µA constant ground current over load (typically 85µA).
The MIC5247 provides a very low-noise output, ideal for
RF applications where quiet voltage sources are required.
A noise bypass pin is also available for further reduction of
output noise.
Designed specifically for handheld and battery-powered de-
vices, the MIC5247 provides a logic compatible enable pin.
When disabled, power consumption drops nearly to zero.
The MIC5247 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, a push-
pull output for faster transient response, and an active clamp
to speed up device turnoff. Available in the 6-pin 2mm × 2mm
MLF™ package and the IttyBitty® SOT-23-5 package, the
MIC5247 also offers a range of fixed output voltages.
All support documentation can be found on Micrel’s web site
at www.micrel.com.
Typical Application
1 5
2
34
COUT
CBYP
Enable
Shutdown
EN
VOUT
(optional)
MIC5247-x.xBM5
EN (pin 3) may be
connected directly
to IN (pin 1).
VIN
MIC5247
150mA Low-Voltage µCap Linear Regulator
Features
• Ultra-low noise
• Low-voltage outputs
• Load independent, ultra-low ground current: 85µA
• 150mA output current
• Current limiting
• Thermal shutdown
• Tight load and line regulation
• “Zero” off-mode current
• Stability with low-ESR capacitors
• Fast transient response
• Logic-controlled enable input
Applications
• Cellular phones and pagers
• Cellular accessories
• Battery-powered equipment
• Laptop, notebook, and palmtop computers
• PCMCIA VCC and VPP regulation/switching
• Consumer/personal electronics
• SMPS post-regulator/DC-to-DC modules
• High-efficiency linear power supplies
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
MIC5247-x.xBML
1
EN 6CBYP
(optional)
VIN VOUT
COUT
5
4
2
3
ENABLE
SHUTDOWN
Ultra-Low-Noise Regulator Application
MIC5247 Micrel, Inc.
M9999-022406 2 February 2006
Pin Configuration
IN
OUTBYP
EN
LUxx/
NUxx
13
4 5
2
GND
MIC5247-x.xBM5 / YM5
MIC5247-x.xBD5 / YM5
(Top View)
1EN
GND
IN
6 BYP
NC
OUT
5
4
2
3
MIC5247-x.xBML / YML
6-Pin 2mm × 2mm MLF™ (ML)
(Top View)
Ordering Information
Part Number Voltage* Junction
Temp. Range Package
Standard Marking Pb-Free Marking**
MIC5247-1.5BM5 LU15 MIC5247-1.5YM5 LU15 1.5V –40ºC to +125ºC SOT-23-5
MIC5247-1.6BM5 LU16 MIC5247-1.6YM5 LU16 1.6V –40ºC to +125ºC SOT-23-5
MIC5247-1.8BM5 LU18 MIC5247-1.8YM5 LU18 1.8V –40ºC to +125ºC SOT-23-5
MIC5247-1.85BM5 LU1J MIC5247-1.85YM5 LU1J 1.85V –40ºC to +125ºC SOT-23-5
MIC5247-2.0BM5 LU20 MIC5247-2.0YM5 LU20 2.0V –40ºC to +125ºC SOT-23-5
MIC5247-2.1BM5 LU21 MIC5247-2.1YM5 LU21 2.1V –40ºC to +125ºC SOT-23-5
MIC5247-2.2BM5 LU22 MIC5247-2.2YM5 LU22 2.2V –40ºC to +125ºC SOT-23-5
MIC5247-2.4BM5 LU24 MIC5247-2.4YM5 LU24 2.4V –40ºC to +125ºC SOT-23-5
MIC5247-1.8BD5 NU18 MIC5247-1.8YD5 NU18 1.8V –40ºC to +125ºC Thin SOT-23-5
MIC5247-2.0BD5 NU20 MIC5247-2.0YD5 NU20 2.0V –40ºC to +125ºC Thin SOT-23-5
MIC5247-1.5BML U15 MIC5247-1.5YML U15 1.5V –40ºC to +125ºC 6-Pin 2mm x 2mm MLF™
MIC5247-1.6BML U16 MIC5247-1.6YML U16 1.6V –40ºC to +125ºC 6-Pin 2mm x 2mm MLF™
MIC5247-1.8BML U18 MIC5247-1.8YML U18 1.8V –40ºC to +125ºC 6-Pin 2mm x 2mm MLF™
MIC5247-1.85BML U1J MIC5247-1.85YML U1J 1.85V –40ºC to +125ºC 6-Pin 2mm x 2mm MLF™
* Other voltage options available, please contact Micrel Marketing for details.
** Over and under bar ( ) (__) symbols may not be to scale.
Pin Description
Pin Number Pin Number Pin Name Pin Function
SOT-23-5 MLF™-6
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 0.01pF 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 to ground pin.
MIC5247 Micrel, Inc.
February 2006 3 M9999-022406
Electrical Characteristics(4)
VIN = VOUT + 1.0V; VIN = VEN; IOUT = 100µA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; unless noted.
Symbol Parameter Conditions Min Typ Max Units
VO Output Voltage Accuracy IOUT = 0mA –1 1 %
–2 2 %
ΔVLNR Line Regulation VIN = 2.7V to 6V –0.3 +0.3 %/V
ΔVLDR Load Regulation IOUT = 0.1mA to 150mA(5) 2 3 %
Load Regulation for 1.5V and 1.6V IOUT = 0.1mA to 150mA, VOUT = 1.5V or 1.6V 3 4 %
VIN – VOUT Dropout Voltage IOUT = 150mA(6) 150 mV
IQ Quiescent Current VEN ≤ 0.4V (shutdown) 0.2 1 µA
IGND Ground Pin Current(7) IOUT = 0mA 85 150 µA
IOUT = 150mA 85 150 µA
PSRR Power Supply Rejection f ≤ 1kHz 50 dB
ILIM Current Limit VOUT = 0V 160 300 mA
en Output Voltage Noise COUT = 10µF, CBYP = 0.01µF, 30 µVrms
f = 10Hz to 100kHz
Enable Input
VIL Enable Input Logic-Low Voltage VIN = 2.7V to 5.5V, regulator shutdown 0.8 0.4 V
VIH Enable Input Logic-High Voltage VIN = 2.7V to 5.5V, regulator enabled 1.6 1 V
IEN Enable Input Current VIL ≤ 0.4V 0.01 µA
VIH ≥ 1.6V 0.01 µA
Shutdown Resistance Discharge 500 Ω
Thermal Protection
Thermal Shutdown Temperature 150 °C
Thermal Shutdown Hysteresis 10 °C
Notes:
1. Exceeding the absolute maximum ratings may damage the device.
2. The device is not guaranteed to function outside its operating ratings.
3. Devices are ESD sensitive. Handling precautions recommended.
4. Specification for packaged product only.
5. 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.
6. Dropout voltage is defined as the input-to-output differential at which the output voltage drops 2% below its nominal value measured a1V 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 volt-
age is 2.7V.
7. Ground pin current is the regulator quiescent current plus pass transistor base current. The total current drawn from the supply is the sum of the load
current plus the ground pin current.
Absolute Maximum Ratings(1)
Supply Input Voltage (VIN) ....................................0V to +7V
Enable Input Voltage (VEN) ...................................0V to VIN
Junction Temperature (TJ) ....................................... +150°C
Storage Temperature (TS) ........................ –65°C to +150°C
Lead Temperature (soldering, 5 sec.) ........................ 260°C
ESD Rating(3)
Operating Ratings(2)
Input Voltage (VIN) .......................................... +2.7V to +6V
Enable Input Voltage (VEN) ...................................0V to VIN
Junction Temperature (TJ) ........................ –40°C to +125°C
Package Thermal Resistance
SOT-23-5 (θJA) .................................................. 235°C/W
2mm × 2mm MLF™ (θJA) .................................... 90°C/W
MIC5247 Micrel, Inc.
M9999-022406 4 February 2006
Typical Characteristics
0
10
20
30
40
50
60
70
80
90
01
x1 1
01x1 2
01
x1 3
01x1 4
01
x1 5
01
x1 6
)Bd(RRSP
FREQUENCY (Hz)
Power Supply Rejection
Ratio
C
BYP
= 0
C
BYP
= 0.01µF
C
BYP
= 1µF
I
L
= 100µA
V
IN
= 3.4V
V
OUT
= 2.4V
C
OUT
= 10µF Ceramic
0
10
20
30
40
50
60
70
01
x1
1
01x1
2
01
x1
3
01x1
4
01x1
5
01
x1
6
)Bd
(
RR
S
P
FREQUENCY (Hz)
Power Supply Rejection
Ratio
C
BYP
= 0
0.01µF
1µF
I
L
= 50mA
V
IN
= 3.4V
V
OUT
= 2.4V
C
OUT
=10µF Ceramic
0
10
20
30
40
50
60
01x1 1
0
1
x1 2
01x1 3
0
1x
14
01x1 5
0
1
x1 6
)
Bd(R
R
SP
FREQUENCY (Hz)
Power Supply Rejection
Ratio
C
BYP
= 0
0.01µF
1µF
0
20
40
60
80
100
-40 -10 20 50 80 110 140
(
TN
ERRU
C
DNU
ORG µ )A
TEMPERATURE (°C)
Ground Pin Current
I
LOAD
= 100µA
0
20
40
60
80
100
0 1 2 3 4
(TN
E
RRUC
DN
UORG µ )A
INPUT VOLTAGE (V)
Ground Pin Current
ILOAD = 100µA
0
20
40
60
80
100
0 1 2 3 4
(TN
ERR
UC
DNU
ORG µ )A
INPUT VOLTAGE (V)
Ground Pin Current
I
LOAD
= 150mA
0
1
2
3
0 1 2 3 4
)
V(
TU
OEG
AT
LOV
INPUT VOLTAGE (V)
Dropout Characteristics
ILOAD = 100µA
ILOAD =
150mA
0
10
20
30
40
50
60
)B
d
(RRSP
FREQUENCY (Hz)
Power Supply Rejection
Ratio
CBYP = 0
0.01 F
1 F
IL= 150mA
VIN = 3.4V
VOUT = 2.4V
COUT = 10 F Ceramic
10 100 1k 10k 100k 1M
0
20
40
60
80
100
-40 -10 20 50 80 110 140
(
T
N
E
RRUC
DN
U
OR
G µ )A
TEMPERATURE (°C)
Ground Pin Current
ILOAD = 150mA
1x10
-8
1x10
-7
1x10
-6
1x10
-5
)
z
Htr/V(YT
IS
N
E
DE
S
IO
N
LARTCEPSTUPTUO
FREQUENCY (Hz)
Noise Performance
C
BYP
= 0
C
BYP
= 0.01 F
V
IN
= 2.8V
V
OUT
= 1.8V
C
OUT
= 4.7 F I
LOAD
= 50mA
10 100 1k 10k 100k 1M
70
71
72
73
74
75
01x1
1-
01x1
0
01x1
1
01x1
2
01x1
3
(TNER
RU
C
D
NUORG µ )A
OUTPUT CURRENT (mA)
Ground Current
vs. Output Current
V
IN
= V
OUT
+ 1
0
100
200
300
400
500
-40 -10 20 50 80 110 140
)
Am
(
T
N
E
RR
U
C
T
I
U
CRIC
T
RO
H
S
TEMPERATURE (°C)
Short Circuit Current
vs. Temperature
VOUT
= 0
MIC5247 Micrel, Inc.
February 2006 5 M9999-022406
Typical Characteristics, cont.
2.3
2.4
2.5
-40 -10 20 50 80 110 140
)V(EGATLOVTUPTUO
TEMPERATURE (°C)
Output Voltage
vs. Temperature
ILOAD = 100µA
0
50
100
150
200
01x1 5-
01x1 4-
01x1 3-
01x1 2-
01x1 1-
01x1 0
01x1 1
(
E
M
I
T µ )s
BYPASS CAPACITOR
(µ
F
)
Turn-On Time
vs. Bypass Capacitance
Rise Time
Prop Delay
COUT = 10µF
ILOAD = 100mA
MIC5247 Micrel, Inc.
M9999-022406 6 February 2006
Load Transient Response
TIME (100µs/div.)
COUT = 10µF
CBYP = 0
VIN = 3.4V
VOUT = 2.4V
100mA
100µA
Line Transient Response
TIME (500µs/div.)
COUT = 10µF
VOUT = 2.4V
ILOAD = 100µA
4.4V
3.4V
Functional Characteristics
MIC5247 Micrel, Inc.
February 2006 7 M9999-022406
Block Diagram
Reference
Voltage
Startup/
Shutdown
Control
EN
Quickstart/
Noise
Cancellation
Under-
voltage
Lockout
Thermal
Sensor
IN
FAUL T
Error
Amplifier
Current
Amplifier
GND
B Y P
OUT
AC TIVE SH UTD OWN
PU L L
UP
PU L L
DOWN
MIC5247 Micrel, Inc.
M9999-022406 8 February 2006
Applications Information
Enable/Shutdown
The MIC5247 comes with an active-high enable pin that can
disable the regulator. 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 volt-
age. 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 capaci-
tance is more than 10 inches away from the device, or when
the supply is a battery.
Output Capacitor
The MIC5247 requires an output capacitor for stability. The
design requires 1µF or greater on the output to maintain stabil-
ity. The capacitor can be a low-ESR ceramic chip capacitor.
The MIC5247 has been designed to work specifically with
low-cost, small chip capacitors. Tantalum capacitors can also
be used for improved capacitance over temperature. The
value of the capacitor can be increased without bound.
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 without bound, further
reducing noise and improving PSRR. Turn-on time remains
constant with respect to bypass capacitance. Refer to the
“Typical Characteristics” section for a graph of turn-on time
vs. bypass capacitor.
Transient Response
The MIC5247 implements a unique output stage to dramati-
cally 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
(85µA).
Active Shutdown
The MIC5247 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 dis-
charge, de-energizing the load.
Thermal Considerations
The MIC5247 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 dis-
sipation of the package, use the junction-to-ambient thermal
resistance of the device and the following basic equation:
P max T max T
DJ 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 examples of junction-to-
ambient thermal resistance for the MIC5247.
Package
θJA
Recommended
θJA
1” Square
θJC
Minimum Footprint Copper Clad
SOT-23-5 (M5) 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 V V I V I
D IN OUT OUT IN GND
= −
(
)
× + ×
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 MIC5247-2.4BM5 at room
temperature with a minimum footprint layout, the maximum
input voltage for a set output current can be determined as
follows:
P max 125 C 25 C
235 C/W
P max 425mW
D
D
( )
( )
=° − °
°
=
The junction-to-ambient thermal resistance for the minimum
footprint is 235°C/W, from Table 1. The maximum power dis-
sipation must not be exceeded for proper operation. Using
the output voltage of 2.4V 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.
425mW = (VIN – 2.4V) 150mA
425mW = VIN ×150mA – 360mW
785mW = VIN×150mA
VIN(max) = 5.2V
Therefore, a 2.4V application at 150mA of output current
can accept a maximum input voltage of 5.2V in a SOT-23-5
package. For a full discussion of heat sinking and thermal
effects on voltage regulators, refer to the “Regulator Ther-
mals” section of Micrel’s Designing with Low-Dropout Voltage
Regulators handbook.
Fixed Regulator Applications
1 5
2
3 4
1µF
0.01µF
VOU T
MIC5247-x.xBM5
VIN
Figure 1. Ultra-Low-Noise Fixed Voltage Application
MIC5247 Micrel, Inc.
February 2006 9 M9999-022406
Figure 1 includes a 0.01µF capacitor for low-noise opera-
tion and shows EN (pin 3) connected to IN (pin 1) for an
application where enable/shutdown is not required. COUT =
1µF minimum.
1 5
2
3 4
1.0µF
Enable
Shutdown
EN
VOU T
MIC5247-x.xBM5
VIN
Figure 2. Low-Noise Fixed Voltage Application
Figure 2 is an example of a low-noise configuration where
CBYP is not required. COUT = 1µF minimum.
MIC5247 Micrel, Inc.
M9999-022406 10 February 2006
Package Information
SOT-23-5 (M)
TSOT-23-5 (D5)
MIC5247 Micrel, Inc.
February 2006 11 M9999-022406
MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 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 at Purchaser’s own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2004 Micrel, Incorporated.
6-Pin MLF™ (ML)