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MIC5237
Micrel
MIC5237
500mA Low-Dropout Regulator Preliminary Information
General Description
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 eta PNPTM process with a PNP pass element, these regulators feature less than 300mV dropout voltage and typically 8mA ground current at full load. 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.
Features
* 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
Applications
* * * * * Portable and laptop computers Desktop computer Battery chargers SMPS post-regulator/dc-to-dc modules Consumer and personal electronics
For space-critical applications and improved performance, see the MIC5209 and MIC5219. For output current requirements up to 750mA, see the MIC2937.
Ordering Information
Part Number MIC5237-2.5BT MIC5237-2.5BU MIC5237-3.3BT MIC5237-3.3BU MIC5237-5.0BT MIC5237-5.0BU Voltage 2.5V 2.5V 3.3V 3.3V 5.0V 5.0V Junct. Temp. Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C Package TO-220 TO-263 TO-220 TO-263 TO-220 TO-263
Typical Application
VIN 5.6V MIC5237-5.0 IN 1.0F OUT GND 1.0F tantalum VOUT 5.0V 3%
Micrel, Inc. * 1849 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 944-0970 * http://www.micrel.com
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MIC5237
MIC5237
Micrel
Pin Configuration
3
TAB
OUT GND IN
2 1
MIC5237-x.xBT (TO-220-3)
3
TAB
OUT GND IN
2 1
MIC5237-x.xBU (TO-263-3)
Pin Description
Pin No. 1 2, TAB 3 Pin Name IN GND OUT Pin Function Supply Input Ground: TO-220 and TO-263 pin 2 and TAB are internally connected. Regulator Output
Absolute Maximum Ratings
Input Voltage (VIN) ........................................ -20V to +20V Power Dissipation (PD) ............................ Internally Limited Junction Temperature (TJ) ....................... -40C to +125C Lead Temperature (soldering, 5 sec.) ....................... 260C
Operating Ratings
Input Voltage (VIN) ....................................... +2.5V to +16V Junction Temperature (TJ) ....................... -40C to +125C Package Thermal Resistance TO-220 (JA) ....................................................... 55C/W TO-220 (JC) ......................................................... 3C/W TO-263 (JC) ......................................................... 3C/W
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Electrical Characteristics
VIN = VOUT + 1.0V; COUT = 4.7F, IOUT = 100A; TJ = 25C, bold values indicate -40C TJ +125C; unless noted. Symbol VOUT VOUT/T VOUT/VOUT VOUT/VOUT VIN - VOUT Parameter Output Voltage Accuracy Output Voltage Temperature Coefficient Line Regulation Load Regulation Dropout Voltage, Note 4 Conditions variation from nominal VOUT Note 2 VIN = VOUT + 1V to 16V 0.015 IOUT = 100A to 500mA, Note 3 IOUT = 100A IOUT = 50mA IOUT = 150mA IOUT = 500mA IGND Ground Pin Current, Note 5 IOUT = 100A IOUT = 50mA IOUT = 150mA IOUT = 500mA PSRR ILIMIT VOUT/PD eno
Note 1:
Min -3 -5
Typical
Max 3 5
Units % % ppm/C
40 0.05 0.1 0.5 0.7 70 90 190 280 350 450 600 700 130 170 650 900 2.5 3.0 15 20
%/V %/V % % mV mV mV mV mV mV mV mV A A A A mA mA mA mA dB
0.05 10 115 165 300 80 350 1.8 8 75 700 0.05 500
Ripple Rejection Current Limit Thermal Regulation Output Noise
f = 120Hz VOUT = 0V Note 6 VOUT = 5.0V, IOUT = 50mA, COUT = 2.2F
900 1000
mA %/W
nV/ Hz
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, JA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: PD(max) = (TJ(max) - TA) / JA. 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. Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are tested for load regulation in the load range from 100A to 500mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification. 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. 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. 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.
Note 2: Note 3: Note 4: Note 5: Note 6:
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MIC5237
Micrel
Block Diagram
VIN
IN
OUT
VOUT COUT
Bandgap Ref.
Current Limit Thermal Shutdown MIC5237-x.x GND
Fixed Regulator
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Typical Characteristics
Power Supply Rejection Ratio
0 -20 PSRR (dB) -40 -60 -80 IOUT = 100A COUT = 1F VIN = 6V VOUT = 5V PSRR (dB) 0 -20 -40 -60 -80 IOUT = 1mA COUT = 1F
Power Supply Rejection Ratio
VIN = 6V VOUT = 5V PSRR (dB) 0 -20 -40 -60 -80
Power Supply Rejection Ratio
VIN = 6V VOUT = 5V
IOUT = 100mA COUT = 1F
-100 1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
-100 1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
-100 1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
Power Supply Ripple Rejection vs. Voltage Drop
60 RIPPLE REJECTION (dB) 50 40 30 20 10 0 0 COUT = 1F 0.1 0.2 0.3 VOLTAGE DROP (V) 0.4 NOISE (V/Hz) 1mA 10 1 0.1 0.01 0.001
Noise Performance
100mA 10mA
10mA
IOUT = 100mA
VOUT = 5V COUT = 10F electrolytic
1mA
0.0001 10 100 1k 10k 100k 1M 10M 1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7 FREQUENCY (Hz)
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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 x output current and input voltage x ground current.
PD = (VIN - VOUT ) x IOUT + VIN x IGND
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. Input Capacitor A 1F 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 An output capacitor is required between OUT and GND to prevent oscillation. 1F 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 5 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 -30C, solid tantalums are recommended for operation below -25C. At lower values of output current, less output capacitance is needed for output stability. The capacitor can be reduced to 0.47F for current below 10mA or 0.33F for currents below 1mA. For 2.5V applications a 22F output capacitor is recommended to reduce startup voltage overshoot. No-Load Stability 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 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 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-
[
](
)
PD = [(13V - 5V) x 500mA] + (13V x 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. TJ(MAX) = 125C JC = junction-to-case thermal resistance CS = case-to-sink thermal resistance JA = junction-to-ambient thermal resistance SA = 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 = 25C that does not exceed the maximum operating junction temperature.
JA =
TJ(max) - TA PD
SA = JA - JC
CS is approximately 1C/W and JC for the TO-220 is 3C/W in this example. JA = 125 - 25 4.260W
JA = 23.5C/W
SA = 23.5C/W - (3C/W + 1C/W )
SA = 19.5C/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. 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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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)
0.050 0.005 (1.27 0.13)
0.590 0.005 (14.99 0.13)
7
0.818 0.005 (20.78 0.13)
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) 0.100 0.005 (2.54 0.13)
0.030 0.003 (0.76 0.08)
0.018 0.008 (0.46 0.020)
0.100 0.020 (2.54 0.51) DIMENSIONS: INCH (MM)
3-Lead TO-220 (T)
0.4050.005 0.065 0.010 202 0.0500.005
0.176 0.005 0.050 0.005
0.3600.005 0.6000.025 SEATING PLANE 0.004 +0.004 -0.008
0.100 BSC DIM. = INCH
0.050
8 MAX 0.015 0.002
0.100 0.01
3-Lead TO-263 (U)
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MIC5237
Micrel
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
USA
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
WEB
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. (c) 2000 Micrel Incorporated
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January 2000

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