MIC37100/37101/37102
1A Low-Voltage µCap LDO
Super eta PNP is a registered trademark of Micrel, Inc.
PowerPC is a registered trademark of IBM Corporation
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 2007
M9999-090607
General Description
The MIC37100, MIC37101, and MIC37102 are 1A low-
dropout, linear voltage regulators that provide low-voltage,
high-current output from an extremely small package.
Utilizing Micrel’s proprietary Super eta PNP
®
pass
element, the MIC37100/01/02 offers extremely low dropout
(typically 280mV at 1A) and low ground current (typically
11mA at 1A).
The MIC37100 is a fixed output regulator offered in the
SOT-223 package. The MIC37101 and MIC37102 are
fixed and adjustable regulators, respectively, in a thermally
enhanced power 8-pin SOIC (small outline package) and
the SOT-223 package. The MIC37102 is also available in
the S-PAK power package, for applications that require
higher power dissipation or higher operating ambient
temperatures.
The MIC37100/01/02 is ideal for PC add-in cards that
need to convert from standard 5V to 3.3V, 3.3V to 2.5V or
2.5V to 1.8V or lower. A guaranteed maximum dropout
voltage of 500mV over all operating conditions allows the
MIC37100/01/02 to provide 2.5V from a supply as low as
3V and 1.8V from a supply as low as 2.3V.
The MIC37100/01/02 is fully protected with overcurrent
limiting and thermal shutdown. Fixed output voltages of
1.5V, 1.65V, 1.8V, 2.5V and 3.3V are available on
MIC37100/01 with adjustable output voltages to 1.24V on
MIC37102.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
• Fixed and adjustable output voltages to 1.24V
• µCap Regulator, 10µF ceramic output capacitor stable
• 280mV typical dropout at 1A
– Ideal for 3.0V to 2.5V conversion
– Ideal for 2.5V to 1.8V, 1.65V or 1.5V conversion
• 1A minimum guaranteed output current
• 1% initial accuracy
• Low ground current
• Current limiting and thermal shutdown
• Reversed-leakage protection
• Fast transient response
• Low-profile SOT-223 package
• Power SO-8 package
• S-PAK package (MIC37102 only)
Applications
• LDO linear regulator for PC add-in cards
• PowerPC
®
power supplies
• High-efficiency linear power supplies
• SMPS post regulator
• Multimedia and PC processor supplies
• Battery chargers
• Low-voltage microcontrollers and digital logic
___________________________________________________________________________________________________________
Typical Application
IN 2.5V
V
IN
3.3V
10F
ceramic
OUT
GND
MIC37100
2.5V/1A Regulator
0
50
100
150
200
250
300
350
0 0.25 0.5 0.75 1
DROPOUT (mV)
OUTPUT CURRENT (A)
Dropout
vs. Output Current
2.5V
OUT
3.3V
OUT
Micrel, Inc. MIC37100/37101/37102
September 2007
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Ordering Information
Part Number
Standard Pb-Free /
RoHS Compliant
Voltage Temperature Range Package
MIC37100-1.5BS MIC37100-1.5WS* 1.5V –40° to +125°C SOT-223
MIC37100-1.65BS MIC37100-1.65WS* 1.65V –40° to +125°C SOT-223
MIC37100-1.8BS MIC37100-1.8WS* 1.8V –40° to +125°C SOT-223
MIC37100-2.5BS MIC37100-2.5WS* 2.5V –40° to +125°C SOT-223
MIC37100-3.3BS MIC37100-3.3WS* 3.3V –40° to +125°C SOT-223
MIC37101-1.5BM MIC37101-1.5YM 1.5V –40° to +125°C 8-Pin SOIC
MIC37101-1.65BM MIC37101-1.65YM 1.65V –40° to +125°C 8-Pin SOIC
MIC37101-1.8BM MIC37101-1.8YM 1.8V –40° to +125°C 8-Pin SOIC
Contact Factory MIC37101-2.1YM 2.1V –40° to +125°C 8-Pin SOIC
MIC37101-2.5BM MIC37101-2.5YM 2.5V –40° to +125°C 8-Pin SOIC
MIC37101-3.3BM MIC37101-3.3YM 3.3V –40° to +125°C 8-Pin SOIC
MIC37102BM MIC37102YM Adj. –40° to +125°C 8-Pin SOIC
MIC37102BR MIC37102WR* Adj. –40° to +125°C 5-Pin S-PAK
* RoHS compliant with ‘high-melting solder’ exemption.
Pin Configur ation
IN OUTGND
132
TAB
GND
TAB
5 ADJ
4 OUT
3 GND
2IN
1EN
SOT-223 (S)
MIC37100-x.x (Fixed) 5-Pin S-PAK (R)
MIC37102 (Adjustable)
1EN
IN
OUT
FLG
8 GND
GND
GND
GND
7
6
5
2
3
4
1EN
IN
OUT
ADJ
8 GND
GND
GND
GND
7
6
5
2
3
4
8-Pin SOIC
MIC37101-x.x (Fixed) 8-Pin SOIC
MIC37102 (Adjustable)
Micrel, Inc. MIC37100/37101/37102
September 2007
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Pin Description
Pin Number
MIC37100
SOT-223
Pin Number
MIC37101
SOIC-8
Pin Number
MIC37102
SOIC-8
Pin Number
MIC37102
S-PAK
Pin Name Pin Description
— 1 1 1 EN
Enable (Input): CMOS-compatible control input. Logic
high = enable, logic low or open = shutdown.
1 2 2 2 IN Supply (Input).
3 3 3 4 OUT Regulator Output.
— 4 — — FLG Flag (Output): Open-collector error flag output. Active
low = output under voltage.
— — 4 5 ADJ
Adjustment Input: Feedback input. Connect to resistive
voltage-divider network.
2, TAB 5–8 5–8 3, TAB GND Ground.
Micrel, Inc. MIC37100/37101/37102
September 2007
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M9999-090607
Absolute Maximum Ratings(1)
Supply Voltage (V
IN
).......................................... 0V to +6.5V
Enable Voltage (V
EN
)...................................................+6.5V
Lead Temperature (soldering, 5 sec.)........................ 260°C
Storage Temperature (T
s
) .........................–65°C to +150°C
ESD Rating
(3)
Operating Ratings(2)
Supply Voltage (V
IN
)...................................... +2.25V to +6V
Enable Voltage (V
EN
)............................................ 0V to +6V
Maximum Power Dissipation (P
D(max)
)
(4)
Junction Temperature (T
J
) ........................–40°C to +125°C
Package Thermal Resistance
SOT-223 (θ
JC
) ....................................................15°C/W
SOIC-8 (θ
JC
).......................................................20°C/W
S-PAK-5 (θ
JC
).......................................................2°C/W
Electrical Characteristics
V
IN
= V
OUT
+ 1V; V
EN
= 2.25V; T
J
= 25°C, bold values indicate –40°C< T
J
< +125°C, unless noted.
Symbol Parameter Condition Min Typ Max Units
Output Voltage 10mA
10mA I
OUT
1A, V
OUT
+ 1V V
IN
6V
–1
–2
1
2
%
%
Line Regulation I
OUT
= 10mA, V
OUT
+ 1V V
IN
6V 0.06 0.5 %
V
OUT
Load Regulation V
IN
= V
OUT
+ 1V, 10mA I
OUT
1A 0.2 1 %
V
OUT
/T Output Voltage Temp. Coefficient
(6)
40 pm/°C
I
OUT
= 100mA, V
OUT
= –1% 125 200 mV
I
OUT
= 500mA, V
OUT
= –1% 210 350 mV
I
OUT
= 750mA, V
OUT
= –1% 250 400 mV
V
DO
Dropout Voltage
(6)
I
OUT
= 1A, V
OUT
= –1% 280 500 mV
I
OUT
= 100mA, V
IN
= V
OUT
+ 1V 650 µA
I
OUT
= 500mA, V
IN
= V
OUT
+ 1V 3.5 mA
I
OUT
= 750mA, V
IN
= V
OUT
+ 1V 6.7 mA
I
GND
Ground Current
(7)
I
OUT
= 1A, V
IN
= V
OUT
+ 1V 11 25 mA
I
OUT(lim)
Current Limit V
OUT
= 0V, V
IN
= V
OUT
+ 1V 1.6 2.5 A
Enable Input
logic low (off) 0.8 V V
EN
Enable Input Voltage
logic high (on) 2.25 V
V
EN
= 2.25V 1 10 30 µA I
EN
Enable Input Current
V
EN
= 0.8V 2
4
µA
µA
Flag Output
I
FLG(leak)
Output Leakage Current V
OH
= 6V 0.01 1
2 µA
µA
V
FLG(do)
Output Low Voltage V
IN
= 2.250V, I
OL
, = 250µA 210 500 mV
Low Threshold % of V
OUT
93 %
High Threshold % of V
OUT
99.2 %
V
FLG
Hysteresis 1 %
MIC37102 Only
Reference Voltage 1.228
1.215
1.240 1.252
1.265
V
V
Adjust Pin Bias Current 40 80
120
nA
nA
Micrel, Inc. MIC37100/37101/37102
September 2007
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M9999-090607
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. P
D(max)
= (T
J(max)
– T
A
) ÷
JA
, where
JA
depends upon the printed circuit layout. See “Applications Information” section.
5. Output voltage temperature coefficient is V
OUT
(worst case) ÷ (T
J(max)
– T
J(min)
) where T
J(max)
is +125°C and T
J(min)
is –40°C.
6. V
DO
= V
IN
– V
OUT
when V
OUT
decreases to 98% of its nominal output voltage with V
IN
= V
OUT
+ 1V. For output voltages below 2.25V, dropout voltage is
the input-to-output voltage differential with the minimum input voltage being 2.25V. Minimum input operating voltage is 2.25V.
7. I
GND
is the quiescent current. I
IN
= I
GND
+ I
OUT
.
8. V
EN
0.8V, V
IN
6V, and V
OUT
= 0V.
Micrel, Inc. MIC37100/37101/37102
September 2007
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Typical Characteristics
Micrel, Inc. MIC37100/37101/37102
September 2007
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M9999-090607
Typical Characteristics (continued)
Micrel, Inc. MIC37100/37101/37102
September 2007
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Typical Characteristics (continued)
Micrel, Inc. MIC37100/37101/37102
September 2007
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Functional Characteristics
Micrel, Inc. MIC37100/37101/37102
September 2007
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M9999-090607
Functional Diagrams
Ref.
Thermal
Shut-
down
1.240V
IN OU
T
MIC37100
MIC37100 Fixed Regu l ator Block Diagram
Ref.
Thermal
Shut-
down
1.240V1.180V
EN
IN
FLAG
GND
OUT
MIC37101
MIC37101 Fixed Regu l ator with Flag and Enable Block Diagram
Ref.
Thermal
Shut-
down
1.240V
EN
IN
GN
D
OUT
ADJ
MIC37102
MIC37102 Adjustable Regu lator Blo ck Diagram
Micrel, Inc. MIC37100/37101/37102
September 2007
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M9999-090607
Application Information
The MIC37100/01/02 is a high-performance low-dropout
voltage regulator suitable for moderate to high-current
voltage regulator applications. Its 500mV dropout voltage
at full load and overtemperature makes it especially
valuable in battery-powered systems and as high-
efficiency noise filters in post-regulator applications.
Unlike older NPN-pass transistor designs, where the
minimum dropout voltage is limited by the base-to-emitter
voltage drop and collector-to-emitter saturation voltage,
dropout performance of the PNP output of these devices
is limited only by the low VCE saturation voltage.
A trade-off for the low dropout voltage is a varying base
drive requirement. Micrel’s Super eta PNP
®
process
reduces this drive requirement to only 2% of the load
current.
The MIC37100/01/02 regulator is fully protected from
damage due to fault conditions. Linear current limiting is
provided. Output current during overload conditions is
constant. Thermal shutdown disables the device when the
die temperature exceeds the maximum safe operating
temperature. The output structure of these regulators
allows voltages in excess of the desired output voltage to
be applied without reverse current flow.
MIC37100-x.x
IN OUT
GND
C
IN
C
OUT
V
IN
V
OUT
Figure 1. Capacitor Requirements
Output Capacitor
The MIC37100/01/02 requires an output capacitor to
maintain stability and improve transient response. As a
µCap LDO, the MIC37100/01/02 can operate with
ceramic output capacitors as long as the amount of
capacitance is 10µF or greater. For values of output
capacitance lower than 10µF, the recommended ESR
range is 200m to 2. The minimum value of output
capacitance recommended for the MIC37100/01/02 is
4.7µF.
For 10µF or greater the ESR range recommended is less
than 1. Ultra-low ESR ceramic capacitors are
recommended for output capacitance of 10µF or greater
to help improve transient response and noise reduction at
high frequency. X7R/X5R dielectric-type 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 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.
Input Capacitor
An input capacitor of 1µF or greater is recommended
when the device is more than 4 inches away from the bulk
ac supply capacitance or when the supply is a battery.
Small, surface mount, ceramic chip capacitors can be
used for bypassing. Larger values will help to improve
ripple rejection by bypassing the input to the regulator,
further improving the integrity of the output voltage.
Error Flag
The MIC37101 features an error flag (FLG), which
monitors the output voltage and signals an error condition
when this voltage drops 5% below its expected value. The
error flag is an open-collector output that pulls low under
fault conditions and may sink up to 10mA. Low output
voltage signifies a number of possible problems, including
an overcurrent fault (the device is in current limit) or low
input voltage. The flag output is inoperative during
overtemperature conditions. A pull-up resistor from FLG
to either V
IN
or V
OUT
is required for proper operation. For
information regarding the minimum and maximum values
of pull-up resistance, refer to the graph in the “Typical
Characteristics” section of the data sheet.
Enable Input
The MIC37101 and MIC37102 versions feature an
active-high enable input (EN) that allows on-off control of
the regulator. Current drain reduces to “zero” when the
device is shutdown, with only microamperes of leakage
current. The EN input has TTL/CMOS compatible
thresholds for simple logic interfacing. EN may be
directly tied to V
IN
and pulled up to the maximum supply
voltage
Transient Response and 3.3V to 2.5V or 2.5V to 1.8V,
1.65V or 1.5V Conversion
The MIC37100/01/02 has excellent transient response to
variations in input voltage and load current. The device
has been designed to respond quickly to load current
variations and input voltage variations. Large output
capacitors are not required to obtain this performance. A
standard 10µF output capacitor, is all that is required.
Larger values help to improve performance even further.
By virtue of its low-dropout voltage, this device does not
saturate into dropout as readily as similar NPN-based
designs. When converting from 3.3V to 2.5V or 2.5V to
1.8V, or lower, the NPN based regulators are already
operating in dropout, with typical dropout requirements
of 1.2V or greater. To convert down to 2.5V or 1.8V
Micrel, Inc. MIC37100/37101/37102
September 2007
12
M9999-090607
without operating in dropout, NPN-based regulators
require an input voltage of 3.7V at the very least. The
MIC37100 regulator will provide excellent performance
with an input as low as 3.0V or 2.5V respectively. This
gives the PNP based regulators a distinct advantage
over older, NPN based linear regulators.
Minimum Load Current
The MIC37100/01/02 regulator is specified between
finite loads. If the output current is too small, leakage
currents dominate and the output voltage rises. A 10mA
minimum load current is necessary for proper regulation.
Adjustable Regulator Design
IN
R1
V
IN
R2
EN
OUT
ADJ
GND
MIC37102
ENABLE
SHUTDOWN
V
OUT
C
OUT
⎟
⎠
⎞
⎜
⎝
⎛+= R2
R1
11.240VV
OUT
Figure 2. Adjustable Regulato r with Resistors
The MIC37102 allows programming the output voltage
anywhere between 1.24V and the 6V maximum
operating rating of the family. Two resistors are used.
Resistors can be quite large, up to 1M, because of the
very high input impedance and low bias current of the
sense comparator. The resistor values are calculated by:
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−= 1
1.240
V
R2R1
OUT
Where V
O
is the desired output voltage. Figure 2 shows
component definition. Applications with widely varying
load currents may scale the resistors to draw the
minimum load current required for proper operation (see
above).
Power SOIC-8 Thermal Characteristics
One of the secrets of the MIC37101/02’s performance is
its power SO-8 package featuring half the thermal
resistance of a standard SO-8 package. Lower thermal
resistance means more output current or higher input
voltage for a given package size.
Lower thermal resistance is achieved by joining the four
ground leads with the die attach paddle to create a
single-piece electrical and thermal conductor. This
concept has been used by MOSFET manufacturers for
years, proving very reliable and cost effective for the
user.
Thermal resistance consists of two main elements,
JC
(junction-to-case thermal resistance) and
CA
(case-to-
ambient thermal resistance). See Figure 3.
JC
is the
resistance from the die to the leads of the package.
CA
is the resistance from the leads to the ambient air and it
includes
CS
(case-to-sink thermal resistance) and
SA
(sink-to-ambient thermal resistance).
JA
JC CA
printed circuit board
ground plane
heat sink area
SOIC-8
AMBIENT
Figure 3. Thermal Resistance
Using the power SOIC-8 reduces the
JC
dramatically
and allows the user to reduce
CA
. The total thermal
resistance,
JA
(junction-to-ambient thermal resistance)
is the limiting factor in calculating the maximum power
dissipation capability of the device. Typically, the power
SOIC-8 has a
JC
of 20°C/W, this is significantly lower
than the standard SOIC-8 which is typically 75°C/W.
CA
is reduced because pins 5 through 8 can now be
soldered directly to a ground plane which significantly
reduces the case-to-sink thermal resistance and sink to
ambient thermal resistance.
Low-dropout linear regulators from Micrel are rated to a
maximum junction temperature of 125°C. It is important
not to exceed this maximum junction temperature during
operation of the device. To prevent this maximum
junction temperature from being exceeded, the
appropriate ground plane heat sink must be used.
0
100
200
300
400
500
600
700
0 0.25 0.50 0.75 1.00 1.25 1.50
COPPER AREA (mm
2
)
POWER DISSIPATION (W)
50°C
55°C
65°C
75°C
85°C
T
JA
=
Figure 4. Copper Area vs. Power SO-8
Power Dissipation
Micrel, Inc. MIC37100/37101/37102
September 2007
13 M9999-090607
Figure 4 shows copper area versus power dissipation
with each trace corresponding to a different temperature
rise above ambient.
From these curves, the minimum area of copper
necessary for the part to operate safely can be
determined. The maximum allowable temperature rise
must be calculated to determine operation along which
curve.
T = T
J(max)
– T
A(max)
T
J(max)
= 125°C
T
A(max)
= maximum ambient operating temp-
erature.
For example, the maximum ambient temperature is
50°C, the T is determined as follows:
T = 125°C – 50°C
T = 75°C
Using Figure 4, the minimum amount of required copper
can be determined based on the required power
dissipation. Power dissipation in a linear regulator is
calculated as follows:
P
D
= (V
IN
– V
OUT
) I
OUT
+ V
IN
× I
GND
If we use a 2.5V output device and a 3.3V input at an
output current of 1A, then our power dissipation is as
follows:
P
D
= (3.3V – 2.5V) × 1A + 3.3V × 11mA
P
D
= 800mW + 36mW
P
D
= 836mW
From Figure 4, the minimum amount of copper required
to operate this application at a T of 75°C is 160mm
2
.
Quick Method
Determine the power dissipation requirements for the
design along with the maximum ambient temperature at
which the device will be operated. Refer to Figure 5,
which shows safe operating curves for three different
ambient temperatures: 25°C, 50°C and 85°C. From
these curves, the minimum amount of copper can be
determined by knowing the maximum power dissipation
required. If the maximum ambient temperature is 50°C
and the power dissipation is as above, 836mW, the
curve in Figure 5 shows that the required area of copper
is 160mm
2
.
The
JA
of this package is ideally 63°C/W, but it will vary
depending upon the availability of copper ground plane
to which it is attached.
0
100
200
300
400
500
600
700
800
900
0 0.25 0.50 0.75 1.00 1.25 1.50
COPPER AREA (mm
2
)
POWER DISSIPATION (W)
T
A
=85°C 50°C 25°C
TJ= 125°C
Figure 5. Copper Area vs. Power-SOIC
Power Dissipation
Micrel, Inc. MIC37100/37101/37102
September 2007
14 M9999-090607
Package Information
SOT-223 (S)
5-Pin S-PAK (R)
Micrel, Inc. MIC37100/37101/37102
September 2007
15 M9999-090607
8-Pin SOIC (M)
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.
© 2005 Micrel, Incorporated.
