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MIC5237
500mA Low-Dropout Regulator
General Description
Features
The MIC5237 is a general-purpose low-dropout regulator * Guaranteed 500mA output over the full operating capable of 500mA output current with better than 3% temperature range output voltage accuracy. Using Micrel's proprietary Super * Low 300mV typical dropout voltage at full load eta PNP(R) process with a PNP pass element, these * Extremely tight load and line regulation regulators feature less than 300mV dropout voltage and * Current and thermal limiting typically 8mA ground current at full load. * Reversed-battery protection Designed for applications that require moderate current * TO-220 and TO-263 packages over a broad input voltage range, including hand-held and battery-powered devices, the MIC5237 is intended for * Low temperature coefficient applications that can tolerate moderate voltage drop at * No-load stability higher current. * Low-noise output Key features include low ground current to help prolong battery life, reversed-battery protection, current limiting, over-temperature shutdown, and thermally efficient Applications packaging. The MIC5237 is available in fixed output * Portable and laptop computers voltages only. * Desktop computer For space-critical applications and improved performance, * Battery chargers see the MIC5209 and MIC5219. For output current * SMPS post-regulator/dc-to-dc modules requirements up to 750mA, see the MIC2937. * Consumer and personal electronics Data sheets and support documentation can be found on Micrel's web site at: www.micrel.com. ___________________________________________________________________________________________________________
Typical Application
Super eta PNP is a registered 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 2007
M9999-090607-C
Micrel, Inc.
MIC5237
Ordering Information
Part Number Standard MIC5237-2.5BU MIC5237-3.3BU MIC5237-5.0BT MIC5237-5.0BU Pb-Free MIC5237-2.5YU MIC5237-3.3YU MIC5237-5.0YT MIC5237-5.0YU 2.5V 3.3V 5.0V 5.0V -40 to +125C -40 to +125C -40 to +125C -40 to +125C TO-263-3 TO-263-3 TO-220-3 TO-263-3 Voltage Junction Temp. Range Package
Pin Configuration
TO-220-3 (T)
TO-263-3 (U)
Pin Description
Pin Number 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.
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Absolute Maximum Ratings(1)
Supply Voltage (VIN) ..........................................-20 to +20V Power Dissipation (PD). .............................Internally Limited Lead Temperature (soldering, 5 sec.)........................ 260C
Operating Ratings
Supply 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
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 Condition variation from nominal VOUT Note 2 VIN = VOUT + 1V to 16V 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 Ripple Rejection Current Limit Thermal Regulation Output Noise f = 120Hz VOUT = 0V Note 6 VOUT = 5.0V, IOUT = 50Ma, COUT = 2.2F Min -3 -5 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 20 900 1000 Typ Max 3 5 Units % % ppm/C %/V %/V % % mV mV mV mV mV mV mV mV A A A A mA mA mA mA dB mA mA %/W nV/Hz
0.015 0.05 10 115 165 300 80 350 1.8 8 75 700 0.05 500
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Notes: 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, JA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: PD(max) = (T J(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. 2. Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. 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 100A to 500mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification. 4. Dropout voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured at 1Vdifferential. 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. 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.
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MIC5237
Typical Characteristics
0 -20 PSRR (dB) -40 -60 -80 IOUT = 100A 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 PSRR (dB)
0 -20 -40 -60 -80
Power Supply Rejection Ratio
VIN = 6V VOUT = 5V
-100 1E+11E+21E+31E+41E+51E+61E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
-100 1E+11E+21E+31E+41E+51E+61E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
IOUT = 1mA COUT = 1F
IOUT = 100mA COUT = 1F
-100 1E+11E+21E+31E+41E+51E+61E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
60 RIPPLE REJECTION (dB) 50 40 30 20 10 0
Power Supply Ripple Rejection vs. Voltage Drop
10 1 NOISE (V/ Hz) 0.1 0.01
Noise Performance
100mA 10mA
1mA 10mA IOUT = 100mA
COUT = 1F 0.1 0.2 0.3 VOLTAGE DROP (V) 0.4
0
VOUT = 5V 1mA 0.001 C = 10F OUT electrolytic 0.0001 10 100 1k 10k 100k 1M 10M 1E+11E+2 1E+31E+4 1E+51E+6 1E+7 FREQUENCY (Hz)
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Block Diagram
Fixed Regulator
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MIC5237 read from the data sheet. Assuming the worst case scenario is good design procedure, and the corresponding ground current 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) 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
Application 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. Ultra low-ESR capacitors can cause low-amplitude oscillations and/or under-damped 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 CMOSRAM 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 September 2007 7
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 19.5C/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.
M9999-090607-C
Micrel, Inc.
MIC5237
Package Information
3-Pin TO-220 (T)
3-Pin TO-263 (U)
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MIC5237
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. (c) 2000 Micrel, Incorporated.
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