MIC37252 2.5A, Low Voltage Cap LDO Regulator General Description Features The Micrel MIC37252 is a 2.5A low-dropout linear voltage regulator that provides a low voltage, high current output with a minimum of external components. It offers high precision, low dropout and low ground current. * * * * * * * * * * The MIC37252 operates from an input voltage of 3.0V to6.0V. It is designed to drive digital circuits requiring low voltage at high currents (i.e., PLDs, DSP, microcontroller, etc.). It is available in an adjustable output voltage capable of 1.24V to 5.5V. Features of the MIC37252 LDO include thermal and current limit protection, and reverse current and reverse battery protection. Junction temperature range of the MIC37252 is from -40C to +125C. For higher currents see the MIC3730x family of LDOs. 2.5A minimum guaranteed output current Ideal for 3.3V to 1.8V conversion Stable with ceramic or tantalum capacitor 2.0% initial output tolerance Dropout voltage = 550mV @ 2.5A Excellent line and load regulation specifications Logic controlled shutdown Thermal shutdown and current limit protection Reverse-leakage protection S-Pak and TO-263 packages Applications * * * * * LDO linear regulator for low-voltage digital IC PC add-in cards High efficiency linear power supplies SMPS post regulator Battery charger ____________________________________________________________________________________________________________ Typical Application Adjustable Regulator SuperSwitcher and Super eta PNP are trademarks 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 February 2006 M9999-021606 (408) 955-1690 Micrel, Inc. MIC37252 Ordering Information Part Number Output Current Voltage* Junction Temperature Range Package Standard RoHS Compliant** MIC37252BR MIC37252WR 2.5A Adj. -40 to +125C S-Pak-5 MIC37252BU MIC37252WU 2.5A Adj. -40 to +125C TO-263-5 *For other voltages, please contact Micrel Marketing. **RoHS compliant with "high melting solder" exemption. Pin Configuration S-PAK5 (R) TO-263 (U) Pin Description Pin Number Pin Name 1 EN Enable (Input): CMOS compatible input. Logic high = enable, logic low = shutdown. 2 VIN Input voltage which supplies current to the output power device. 3 GND Ground (TAB is connected to ground on S-Pak). 4 VOUT 5 ADJ February 2006 Pin Function Regulator Output. Adjustable regulator feedback input. Connect to resistor voltage divider. 2 M9999-021606 (408) 955-1690 Micrel, Inc. MIC37252 Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VIN) ......................................................6.5V Enable Input Voltage (VEN)............................................6.5V Power Dissipation .....................................Internally Limited Junction Temperature .........................-40C TJ +125C Storage Temperature ..........................-65C TJ +150C Lead Temperature (soldering, 5sec.)......................... 260C EDS(3) Supply voltage (VIN) ......................................... 3.0V to 6.0V Enable Input Voltage (VEN).................................. 0V to 6.0V Junction Temperature Range .............-40C TJ +125C Maximum Power Dissipation(4) Package Thermal Resistance S-Pak (JC) ..........................................................2C/W TO-263-5 (JC).....................................................2C/W Electrical Characteristics(5) TA = 25C with VIN = VOUT + 1V; VEN = VIN; IL = 10mA, bold values indicate -40C< TJ < +125C, unless otherwise noted. Parameter Condition Min Output Voltage Accuracy IL = 10mA 10mA < IOUT < IL(max), VOUT + 1 VIN 6V Typ Max Units -2 +2 % -3 +3 % Output Voltage Line Regulation VIN = VOUT + 1.0V to 6.0V, IL = 10mA 0.02 0.5 % Output Voltage Load Regulation IL = 10mA to 2.5A 0.2 1 % VIN - VOUT; Dropout Voltage, Note 6 IL = 1.5A 400 500 mV IL = 2.5A 550 1000 mV Ground Pin Current, Note 7 IL = 2.5A 40 60 mA Ground Pin Current in Shutdown VIL 0.5V, VIN = VOUT + 1V 1.0 A Current Limit VOUT = 0; VIN = 3.3V 3 A Start-up Time VEN = VIN, IOUT = 10mA, COUT = 47F 150 250 s Enable Input Enable Input Threshold Regulator enable Enable Pin Input Current VIL 0.8V (Regulator shutdown) V 2.25 Regulator shutdown VIH 2.25V (Regulator enable) Reference Voltage 0.8 V 2 4 A A 1 10 30 A 1.215 1.202 1.240 1.265 1.277 V V 40 80 120 nA nA Adjust Pin Bias Current Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Device is ESD sensitive. Handling precautions recommended. 4. PD(max) = TJ(max) - TA) / JA, where JA, depends upon the printed circuit layout. See "Applications Information." 5. Specification for packaged product only 6. VDO = VIN - VOUT when VOUT decreased to 98% of its nominal output voltage with VIN = VOUT + 1V. For output voltages below 2V, dropout voltage specification does not apply due to a minimum input operating voltage of 3V 7. IGND is the quiescent current. IIN = IGND + IOUT. February 2006 3 M9999-021606 (408) 955-1690 Micrel, Inc. MIC37252 Typical Characteristics 100mA 60 1A 50 2.5A 40 30 20 COUT = 100F Ceramic V = 3.3V 10 IN VOUT = 1.8V 0 1 10 100 1k 10k 100k 1M FREQUENCY (Hz) 200 100 3.3VOUT 2.5A load GROUND CURRENT (mA) 3.5 3 2.5 2 1.5 1 0.5 VOUT = 0V VIN = 4.3V 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE TJ (C) 50 45 40 35 30 25 20 15 10 5 0 1.85 1.84 1.83 1.82 1.81 1.80 1.79 1.78 1.77 1.76 1.75 -40 -20 0 20 40 60 80 100 120 TEMPERATURE C) ( Short Circuit Current vs. Temperature Ground Current vs. Output Current 0 February 2006 0.5 1 1.5 2 2.5 OUTPUT CURRENT (A) 200 100 0 50 45 40 35 30 25 20 15 10 5 0 0 Enable Pin Current vs. Temperature 100mA Load 14 12 10 8 6 4 2 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE C) ( Ground Current vs. Temperature 2.5A 1.5A 5 2.510 2.508 2.506 2.504 2.502 2.500 2.498 2.496 2.494 2.492 2.5V OUT 2.490 0 0.5 1 1.5 2 2.5 OUTPUT CURRENT (A) 4 0.5 1 1.5 2 2.5 OUTPUT CURRENT (A) 16 Ground Current vs. Supply Voltage 0.5A 1 2 3 4 SUPPLY VOLTAGE (V) 0 18 Output Voltage vs. Load Current OUTPUT VOLTAGE (V) GROUND CURRENT (mA) SHORT CIRCUIT CURRENT (A) 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE C) ( 4 300 ENABLE CURRENT (A) 300 30 Dropout Voltage VOUT = 3.3V 400 GROUND CURRENT (mA) 400 2.5A 40 500 Output Voltage vs. Temperature OUTPUT VOLTAGE (V) DROPOUT VOLTAGE (mV) 500 1A 20 COUT = 47F V = 3.3V 10 IN VOUT = 1.8V 0 1 10 100 1k 10k 100k 1M FREQUENCY (Hz) Dropout vs. Temperature 600 600 100mA OUTPUT VOLTAGE (V) PRSS (dB) 50 PSRR (dB) 60 PSRR 70 DROPOUT VOLTAGE (mV) PSRR 70 50 2.5A Load 45 40 35 30 25 20 15 1A Load 10 5 10mA Load 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE C) ( 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.00 Dropout Characteristics 0.5A 1.5A 2.5A 1 2 3 SUPPLY VOLTAGE (V) 4 M9999-021606 (408) 955-1690 Micrel, Inc. MIC37252 Functional Characteristics LoadTransient Response OUTPUT VOLTAGE (200mV/div.) VIN = 3.3V VOUT = 1.8V COUT = 47F 2A OUTPUT CURRENT (1A/div.) VIN = 3.3V VOUT = 1.8V COUT = 47F OUTPUT CURRENT (1A/div.) OUTPUT VOLTAGE (100mV/div.) LoadTransient Response 10mA TIME (400s/div.) 2.5A 10mA TIME (400s/div.) OUTPUT VOLTAGE (20mV/div.) Line Transient Response 5V INPUT VOLTAGE (2V/div.) 3.3V TIME (100s/div.) February 2006 5 M9999-021606 (408) 955-1690 Micrel, Inc. MIC37252 applications where the minimum input voltage is known and is large compared with the dropout voltage. Use a series input resistor to drop excessive voltage and distribute the heat between this resistor and the regulator. The low dropout properties of Micrel Super eta PNP(R) regulators allow significant reductions in regulator power dissipation and the associated heat sink without compromising performance. When this technique is employed, a capacitor of at least 1.0F is needed directly between the input and regulator ground. Refer to Application Note 9 for further details and examples on thermal design and heat sink applications. Application Information The MIC37252 is a high-performance low-dropout voltage regulator suitable for moderate to high-current regulator applications. Its 550mV dropout voltage at full load makes it especially valuable in battery-powered systems and as high-efficiency noise filters in postregulator applications. Unlike older NPN-pass transistor designs, where the minimum dropout voltage is limited by the base-to-emitter voltage drop and collector-toemitter saturation voltage, dropout performance of the PNP output of these devices is limited only by the low VCE saturation voltage. Output Capacitor The MIC37252 requires an output capacitor for stable operation. As a Cap LDO, the MIC37252 can operate with ceramic output capacitors as long as the amount of capacitance is 47F or greater. For values of output capacitance lower than 47F, the recommended ESR range is 200m to 2. The minimum value of output capacitance recommended for theMIC37252 is 10F. A trade off for the low dropout voltage is a varying base drive requirement. Micrel's Super eta PNP(R) process reduces this drive requirement to only 2% to 5% of the load current. The MIC37252 regulator is fully protected from damage due to fault conditions. Current limiting is provided. This limiting is linear; output current during overload conditions is constant. Thermal shutdown disables the device when the die temperature exceeds the maximum safe operating temperature. Transient protection allows device (and load) survival even when the input voltage spikes above and below nominal. The output structure of these regulators allows voltages in excess of the desired output voltage to be applied without reverse current flow. For 47F or greater the ESR range recommended is less than1. Ultra-low ESR, ceramic capacitors are recommended for output capacitance of 47F or greater to help improve transient response and noise reduction at high frequency. X7R/X5R dielectric-type ceramic capacitors are recommended because of their temperature performance. X7R-type capacitors change capacitance by 15% over their operating temperature range and are the most stable type of ceramic capacitors. Z5U and Y5V dielectric capacitors change value by as much as 50% and 60% respectively over their operating temperature ranges. To use a ceramic chip capacitor withY5V dielectric, the value must be much higher than an X7Rceramic capacitor to ensure the same minimum capacitance over the equivalent operating temperature range. The MIC37252 has excellent transient response to variations in input voltage and load current. The device has been designed to respond quickly to load current variations and input voltage variations. Large output capacitors are not required to obtain this performance. A standard 47F output capacitor is all that is required. Larger values help to improve performance even further. Thermal Design Linear regulators are simple to use. The most complicated design parameters to consider are thermal characteristics. Thermal design requires the following application-specific parameters: * Maximum ambient temperature (TA) * Output current (IOUT) * Output voltage (VOUT) * Input voltage (VIN) * Ground current (IGND) First, calculate the power dissipation of the regulator from these numbers and the device parameters from this datasheet. PD = (VIN - VOUT) IOUT + VIN IGND Input Capacitor An input capacitor of 1.0F or greater is recommended when the device is more than 4 inches away from the bulk supply capacitance, or when the supply is a battery. Small, surface-mount chip capacitors can be used for the bypassing. The capacitor should be place within 1" of the device for optimal performance. Larger values will help to improve ripple rejection by bypassing the input to the regulator, further improving the integrity of the output voltage. Where the ground current is approximated by using numbers from the "Electrical Characteristics" or "Typical Characteristics." Then the heat sink thermal resistance is determined with this formula: SA = ((TJ(MAX) - TA)/ PD) - (JC + CS) Where T J(MAX) 125C and CS is between 0C and 2C/W. The heat sink may be significantly reduced in February 2006 6 M9999-021606 (408) 955-1690 Micrel, Inc. MIC37252 input is TTL/CMOS compatible for simple logic interface, but can be connected to up to VIN. When enabled, it draws approximately 15A. Transient Response and 5V to 3.3V or 3.3V to 1.8VConversions The MIC37252 has excellent transient response to variations in input voltage and load current. The device has been designed to respond quickly to load current variations and input voltage variations. Large output capacitors are not required to obtain this performance. A standard 10F output capacitor, preferably tantalum, is all that is required. Larger values help to improve performance even further. Adjustable Regulator Design By virtue of its low dropout voltage, this device does not saturate into dropout as readily as similar NPN-based designs. When converting from 3.3V to 1.8V, the NPNbased regulators are already operating in dropout, with typical dropout requirements of 2V or greater. To convert down to1.8V without operating in dropout, NPN-based regulators require an input voltage of 3.8V at the very least. The MIC37252 regulator will provide excellent performance with an input as low as 3.0V. This gives the PNP-based regulators a distinct advantage over older NPN-based linear regulators. Figure 2. Adjustable Regulator with Resistors The MIC37252 allows programming of the output voltage anywhere between 1.24V and the 5.5V maximum operating rating of the family. Two resistors are used. Resistors values are recommended to be less than 10k in value to improve stability. The resistor values can be sized to draw the mini-mum load current for this device. The resistor values are calculated by: V R1 = R2 OUT - 1 1.240 Minimum Load Current The MIC37252 regulator is specified between finite loads. If the output current is too small, leakage currents dominate and the output voltage rises. A 10mA minimum load current is necessary for proper operation. Where VOUT is the desired output voltage. Figure 2 shows component definition. Applications with widely varying load currents may scale the resistors to draw the minimum load current required for proper operation (see above). Enable Input The MIC37252 also features an enable input for on/off control of the device. Its shutdown state draws "zero" current (only microamperes of leakage). The enable February 2006 7 M9999-021606 (408) 955-1690 Micrel, Inc. MIC37252 Package Information 5-Pin S-PAK (R) 4 1 2 1 1 2 3 4 1 3 5-Pin TO-263 (U) 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) 2002 Micrel, Incorporated. February 2006 8 M9999-021606 (408) 955-1690