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 ßeta PNP® 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 βeta 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 Voltage Junction Temp. Range Package Standard Pb-Free MIC5237-2.5BU MIC5237-2.5YU 2.5V –40° to +125°C TO-263-3 MIC5237-3.3BU MIC5237-3.3YU 3.3V –40° to +125°C TO-263-3 MIC5237-5.0BT MIC5237-5.0YT 5.0V –40° to +125°C TO-220-3 MIC5237-5.0BU MIC5237-5.0YU 5.0V –40° to +125°C TO-263-3 Pin Configuration TO-220-3 (T) TO-263-3 (U) Pin Description Pin Number 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. September 2007 2 M9999-090607-C Micrel, Inc. MIC5237 Absolute Maximum Ratings(1) Operating Ratings Supply Voltage (VIN) ..........................................–20 to +20V Power Dissipation (PD). .............................Internally Limited Lead Temperature (soldering, 5 sec.)........................ 260°C Supply 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 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 Condition 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 ∆VOUT/VOUT Load Regulation IOUT = 100µA to 500mA, Note 3 VIN – VOUT Dropout Voltage, Note 4 IGND Ground Pin Current, Note 5 Min Typ –3 –5 Max Units 3 5 % % ppm/°C 40 0.05 0.1 %/V %/V 0.05 0.5 0.7 % % 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 0.015 PSRR Ripple Rejection f = 120Hz 75 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 September 2007 3 dB 900 1000 mA mA M9999-090607-C Micrel, Inc. MIC5237 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, θJA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: PD(max) = (T J(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. 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 100µA 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. September 2007 4 M9999-090607-C Micrel, Inc. MIC5237 Typical Characteristics Power Supply Rejection Ratio -40 -60 -80 -100 1E+11E+21E+31E+41E+51E+61E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz) 10 50 10mA IOUT = 100mA 20 COUT = 1µF 10 0 0 IOUT = 1mA COUT = 1µF 0.1 0.2 0.3 VOLTAGE DROP (V) September 2007 0.4 -20 Power Supply Rejection Ratio VIN = 6V VOUT = 5V -40 -60 -80 IOUT = 100mA COUT = 1µF -100 1E+11E+21E+31E+41E+51E+61E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz) Noise Performance 1 1mA NOISE (µV/ Hz) RIPPLE REJECTION (dB) 60 30 -60 -100 1E+11E+21E+31E+41E+51E+61E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz) Power Supply Ripple Rejection vs. Voltage Drop 40 -40 -80 IOUT = 100µA COUT = 1µF 0 VIN = 6V VOUT = 5V -20 PSRR (dB) -20 PSRR (dB) 0 VIN = 6V VOUT = 5V PSRR (dB) 0 Power Supply Rejection Ratio 100mA 10mA 0.1 0.01 VOUT = 5V 1mA 0.001 C = 10µF OUT electrolytic 0.0001 10 100 1E+31E+4 1k 10k 1E+51E+6 100k 1M 1E+7 10M 1E+11E+2 FREQUENCY (Hz) 5 M9999-090607-C Micrel, Inc. MIC5237 Block Diagram Fixed Regulator September 2007 6 M9999-090607-C Micrel, Inc. 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 × output current and input voltage × ground current. PD = [(VIN – VOUT) × IOUT] + (VIN × IGND) 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. 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. 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 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 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. 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 –30°C, solid tantalums are recommended for operation below –25°C. 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. θ JA = PD θSA = θJA - θJC θCS is approximately 1°C/W and θJC for the TO-220 is 3°C/W in this example. 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. θ JA = 125 - 25 4.260W θJA = 23.5°C/W θSA = 23.5°C/W – (3°C/W + 1°C/W) θSA = 19.5°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. For a full discussion on voltage regulator thermal effects, please refer to “Thermal Management” in Micrel’s Designing with Low-Dropout Voltage Regulators handbook. 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 TJ(max) - TA 7 M9999-090607-C Micrel, Inc. MIC5237 Package Information 3-Pin TO-220 (T) 3-Pin TO-263 (U) September 2007 8 M9999-090607-C Micrel, Inc. 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. © 2000 Micrel, Incorporated. September 2007 9 M9999-090607-C