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 2 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 3 MIC5237 MIC5237 Micrel Block Diagram VIN OUT IN VOUT COUT Bandgap Ref. Current Limit Thermal Shutdown MIC5237-x.x GND Fixed Regulator MIC5237 4 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. 6 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 7 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 8 January 2000