MICREL MIC5237

MIC5237
Micrel
MIC5237
500mA Low-Dropout Regulator
Preliminary Information
General Description
Features
The MIC5237 is a general-purpose low-dropout regulator
capable of 500mA output current with better than 3% output
voltage accuracy. Using Micrel’s proprietary Super
ßeta PNP™ process with a PNP pass element, these regulators feature less than 300mV dropout voltage and typically
8mA ground current at full load.
• Guaranteed 500mA output over the full operating
temperature range
• Low 300mV typical dropout voltage at full load
• Extremely tight load and line regulation
• Current and thermal limiting
• Reversed-battery protection
• TO-220 and TO-263 packages
• Low temperature coefficient
• No-load stability
• Low-noise output
Designed for applications that require moderate current over
a broad input voltage range, including hand-held and batterypowered devices, the MIC5237 is intended for applications
that can tolerate moderate voltage drop at higher current.
Key features include low ground current to help prolong
battery life, reversed-battery protection, current limiting, overtemperature shutdown, and thermally efficient packaging.
The MIC5237 is available in fixed output voltages only.
Applications
•
•
•
•
•
For space-critical applications and improved performance,
see the MIC5209 and MIC5219. For output current requirements up to 750mA, see the MIC2937.
Portable and laptop computers
Desktop computer
Battery chargers
SMPS post-regulator/dc-to-dc modules
Consumer and personal electronics
Ordering Information
Part Number
Voltage
Junct. Temp. Range
Package
MIC5237-2.5BT
2.5V
–40°C to +125°C
TO-220
MIC5237-2.5BU
2.5V
–40°C to +125°C
TO-263
MIC5237-3.3BT
3.3V
–40°C to +125°C
TO-220
MIC5237-3.3BU
3.3V
–40°C to +125°C
TO-263
MIC5237-5.0BT
5.0V
–40°C to +125°C
TO-220
MIC5237-5.0BU
5.0V
–40°C to +125°C
TO-263
Typical Application
VIN
≥5.6V
MIC5237-5.0
IN
1.0µF
VOUT
5.0V ±3%
OUT
GND
1.0µF
tantalum
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
January 2000
1
MIC5237
MIC5237
Micrel
TAB
Pin Configuration
3
OUT
2
GND
1
IN
TAB
MIC5237-x.xBT
(TO-220-3)
3
OUT
2
GND
1
IN
MIC5237-x.xBU
(TO-263-3)
Pin Description
Pin No.
Pin Name
Pin Function
1
IN
Supply Input
2, TAB
GND
Ground: TO-220 and TO-263 pin 2 and TAB are internally connected.
3
OUT
Regulator Output
Absolute Maximum Ratings
Operating Ratings
Input Voltage (VIN) ........................................ –20V to +20V
Power Dissipation (PD) ............................ Internally Limited
Junction Temperature (TJ) ....................... –40°C to +125°C
Lead Temperature (soldering, 5 sec.) ....................... 260°C
Input Voltage (VIN) ....................................... +2.5V to +16V
Junction Temperature (TJ) ....................... –40°C to +125°C
Package Thermal Resistance
TO-220 (θJA) ....................................................... 55°C/W
TO-220 (θJC) ......................................................... 3°C/W
TO-263 (θJC) ......................................................... 3°C/W
MIC5237
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January 2000
MIC5237
Micrel
Electrical Characteristics
VIN = VOUT + 1.0V; COUT = 4.7µF, IOUT = 100µA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; unless noted.
Symbol
Parameter
Conditions
Min
VOUT
Output Voltage Accuracy
variation from nominal VOUT
∆VOUT/∆T
Output Voltage
Temperature Coefficient
Note 2
∆VOUT/VOUT
Line Regulation
VIN = VOUT + 1V to 16V
Typical
–3
–5
Max
Units
3
5
%
%
40
ppm/°C
0.05
0.1
%/V
%/V
0.05
0.5
0.7
%
%
0.015
∆VOUT/VOUT
Load Regulation
IOUT = 100µA to 500mA, Note 3
VIN – VOUT
Dropout Voltage, Note 4
IOUT = 100µA
10
70
90
mV
mV
IOUT = 50mA
115
190
280
mV
mV
IOUT = 150mA
165
350
450
mV
mV
IOUT = 500mA
300
600
700
mV
mV
IOUT = 100µA
80
130
170
µA
µA
IOUT = 50mA
350
650
900
µA
µA
IOUT = 150mA
1.8
2.5
3.0
mA
mA
IOUT = 500mA
8
15
20
mA
mA
Ground Pin Current, Note 5
IGND
PSRR
Ripple Rejection
f = 120Hz
75
dB
ILIMIT
Current Limit
VOUT = 0V
700
∆VOUT/∆PD
Thermal Regulation
Note 6
0.05
%/W
eno
Output Noise
VOUT = 5.0V, IOUT = 50mA,
COUT = 2.2µF
500
nV/ Hz
900
1000
mA
Note 1:
Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when
operating the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction
temperature, TJ(max), the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. The maximum allowable power
dissipation at any ambient temperature is calculated using: PD(max) = (TJ(max) – TA) ÷ θJA. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. See the “Thermal Considerations” section for
details.
Note 2:
Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 3:
Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are tested for load regulation in the load
range from 100µA to 500mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification.
Note 4:
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.
Note 5:
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.
Note 6:
Thermal regulation is defined as the change in output voltage at a time “t” after a change in power dissipation is applied, excluding load or line
regulation effects. Specifications are for a 500mA load pulse at VIN = 16V for t = 10ms.
January 2000
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MIC5237
MIC5237
Micrel
Block Diagram
VIN
OUT
IN
VOUT
COUT
Bandgap
Ref.
Current Limit
Thermal Shutdown
MIC5237-x.x
GND
Fixed Regulator
MIC5237
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January 2000
MIC5237
Micrel
Typical Characteristics
Power Supply
Rejection Ratio
-40
-60
-80
IOUT = 100µA
COUT = 1µF
-100
1k 1E+4
1E+1
10k 1E+5
1M 1E+7
10M
10 1E+2
100k 1E+6
100 1E+3
FREQUENCY (Hz)
Power Supply
Rejection Ratio
0
VIN = 6V
VOUT = 5V
-20
-20
PSRR (dB)
PSRR (dB)
-20
0
VIN = 6V
VOUT = 5V
PSRR (dB)
0
Power Supply
Rejection Ratio
-40
-60
-80
-40
-60
-100
1k 1E+4
1E+1
10k 1E+5
1M 1E+7
10M
10 1E+2
100k 1E+6
100 1E+3
FREQUENCY (Hz)
Power Supply Ripple Rejection
vs. Voltage Drop
Noise Performance
10
50
1
1mA
40
30
10mA
NOISE (µV/√Hz)
RIPPLE REJECTION (dB)
60
January 2000
IOUT = 100mA
COUT = 1µF
-80
IOUT = 1mA
COUT = 1µF
-100
1k 1E+4
1E+1
10k 1E+5
1M 1E+7
10M
10 1E+2
100k 1E+6
100 1E+3
FREQUENCY (Hz)
IOUT = 100mA
20
0
0.1
0.2
0.3
VOLTAGE DROP (V)
5
0.4
100mA
10mA
0.1
0.01
0.001
COUT = 1µF
10
0
VIN = 6V
VOUT = 5V
VOUT = 5V
COUT = 10µF
electrolytic
1mA
0.0001
1k 1E+4
10 1E+2
1M 1E+7
10k 1E+5
100k 1E+6
10M
1E+1
100 1E+3
FREQUENCY (Hz)
MIC5237
MIC5237
Micrel
rent number can be obtained from the data sheet. First,
calculate the power dissipation of the device. This example
uses the MIC5237-5.0BT, a 13V input, and 500mA output
current, which results in 20mA of ground current, worst case.
The power dissipation is the sum of two power calculations:
voltage drop × output current and input voltage × ground
current.
Applications Information
The MIC5237 is intended for general-purpose use and can be
implemented in a wide variety of applications where 500mA
of output current is needed. It is available in several voltage
options for ease of use. For voltage options that are not
available on the MIC5237, consult the MIC5209 for a 500mA
adjustable LDO regulator, or the MIC5219 for applications
that require only short-duration peak output current.
[
] (
PD = (VIN – VOUT ) × IOUT + VIN × IGND
Input Capacitor
A 1µF capacitor should be placed from IN to GND if there is
more than 10 inches of wire between the input and the ac filter
capacitor or if a battery is used as the input.
Output Capacitor
PD = [(13V – 5V) × 500mA] + (13V × 20mA)
PD = 4.260W
From this number, the heat sink thermal resistance is determined using the regulator’s maximum operating junction
temperature (TJ(max)) and the ambient temperature (TA)
along with the power dissipation number already calculated.
An output capacitor is required between OUT and GND to
prevent oscillation. 1µF minimum is recommended for standard applications. Larger values improve the regulator’s
transient response. The output capacitor value may be increased without limit.
The output capacitor should have an ESR (equivalent series
resistance) of about 5Ω or less and a resonant frequency
above 1MHz. Ultralow-ESR capacitors can cause low-amplitude oscillations and/or underdamped transient response.
Most tantalum or aluminum electrolytic capacitors are adequate; film types will work, but are more expensive. Since
many aluminum electrolytics have electrolytes that freeze at
about –30°C, solid tantalums are recommended for operation
below –25°C.
TJ(MAX) = 125°C
θJC = junction-to-case thermal resistance
θCS = case-to-sink thermal resistance
θJA = junction-to-ambient thermal resistance
θSA = sink-to-ambient thermal resistance
To determine the heat sink thermal resistance, the junctionto-case thermal resistance of the device must be used along
with the case-to-heat sink thermal resistance. These numbers show the heat-sink thermal resistance required at TA =
25°C that does not exceed the maximum operating junction
temperature.
At lower values of output current, less output capacitance is
needed for output stability. The capacitor can be reduced to
0.47µF for current below 10mA or 0.33µF for currents below
1mA.
For 2.5V applications a 22µF output capacitor is recommended to reduce startup voltage overshoot.
No-Load Stability
θ JA =
TJ(max) − TA
PD
θSA = θ JA − θ JC
θCS is approximately 1°C/W and θJC for the TO-220 is 3°C/W
in this example.
The MIC5237 will remain stable and in regulation with no load
(other than the internal voltage divider) unlike many other
voltage regulators. This is especially important in CMOS
RAM keep-alive applications.
Thermal Considerations
θ JA =
Proper thermal design can be accomplished with some basic
design criteria and some simple equations. The following
information is required to implement a regulator design.
VIN = input voltage
VOUT = output voltage
θSA = 19.5°C/W
125 – 25
4.260W
θ JA = 23.5°C/W
θSA = 23.5°C/W – (3°C/W + 1°C/W )
Therefore, a heat sink with a thermal resistance of 19.5° C/W
will allow the part to operate safely and it will not exceed the
maximum junction temperature of the device. The heat sink
can be reduced by limiting power dissipation, by reducing the
input voltage or output current. Either the TO-220 or TO-263
package can operate reliably at 2W of power dissipation
without a heat sink. Above 2W, a heat sink is recommended.
IOUT = output current
TA = ambient operating temperature
IGND = ground current
The regulator ground current, IGND, can be measured or read
from the data sheet. Assuming the worst case scenario is
good design procedure, and the corresponding ground cur-
MIC5237
)
For a full discussion on voltage regulator thermal effects,
please refer to “Thermal Management” in Micrel’s Designing
with Low-Dropout Voltage Regulators handbook.
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January 2000
MIC5237
Micrel
Package Information
0.151 D ±0.005
(3.84 D ±0.13)
0.410 ±0.010
(10.41 ±0.25)
0.108 ±0.005
(2.74 ±0.13)
0.176 ±0.005
(4.47 ±0.13)
0.590 ±0.005
(14.99 ±0.13)
0.818 ±0.005
(20.78 ±0.13)
0.050 ±0.005
(1.27 ±0.13)
7°
0.356 ±0.005
(9.04 ±0.13)
7°
3°
1.140 ±0.010
(28.96 ±0.25)
0.050 ±0.003
(1.27 ±.08)
0.030 ±0.003
(0.76 ±0.08)
0.018 ±0.008
(0.46 ±0.020)
0.100 ±0.005
(2.54 ±0.13)
0.100 ±0.020
(2.54 ±0.51)
DIMENSIONS: INCH
(MM)
3-Lead TO-220 (T)
0.176 ±0.005
0.405±0.005
0.065 ±0.010
20°±2°
0.050 ±0.005
0.050±0.005
0.360±0.005
0.600±0.025
SEATING PLANE
0.004 +0.004
–0.008
0.100 BSC
8° MAX
0.050
0.100 ±0.01
0.015 ±0.002
DIM. = INCH
3-Lead TO-263 (U)
January 2000
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MIC5237
MIC5237
Micrel
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
WEB
USA
http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
© 2000 Micrel Incorporated
MIC5237
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January 2000