MIC37100/37101/37102 Micrel MIC37100/37101/37102 1A Low-Voltage µCap LDO Regulator General Description Features The MIC37100, MIC37101, and MIC37102 are 1A lowdropout, linear voltage regulators that provide low-voltage, high-current output from an extremely small package. Utilizing Micrel’s proprietary Super βeta PNP™ pass element, the MIC37100/01/02 offers extremely low dropout (typically 280mV at 1A) and low ground current (typically 11mA at 1A). The MIC37100 is a fixed output regulator offered in the SOT-223 package. The MIC37101 and MIC37102 are fixed and adjustable regulators, respectively, in a thermally enhanced power 8-lead SOIC (small outline package) and the SOT-223 package. The MIC37102 is also available in the SPAK power package, for applications that require higher power dissipation or higher operating ambient temperatures. The MIC37100/01/02 is ideal for PC add-in cards that need to convert from standard 5V to 3.3V, 3.3V to 2.5V or 2.5V to 1.8V or lower. A guaranteed maximum dropout voltage of 500mV over all operating conditions allows the MIC37100/01/02 to provide 2.5V from a supply as low as 3V and 1.8V from a supply as low as 2.3V. The MIC37100/01/02 is fully protected with overcurrent limiting and thermal shutdown. Fixed output voltages of 1.5V, 1.65V, 1.8V, 2.5V and 3.3V are available on MIC37100/01 with adjustable output voltages to 1.24V on MIC37102. • Fixed and adjustable output voltages to 1.24V µF ceramic output capacitor • µCap Regulator, 10µ stable • 280mV typical dropout at 1A Ideal for 3.0V to 2.5V conversion Ideal for 2.5V to 1.8V, 1.65V or 1.5V conversion • 1A minimum guaranteed output current • 1% initial accuracy • Low ground current • Current limiting and thermal shutdown • Reversed-leakage protection • Fast transient response • Low-profile SOT-223 package • Power SO-8 package • S-PAK package (MIC37102 only) Applications • • • • • • • For other voltages, contact Micrel. LDO linear regulator for PC add-in cards PowerPC™ power supplies High-efficiency linear power supplies SMPS post regulator Multimedia and PC processor supplies Battery chargers Low-voltage microcontrollers and digital logic All support documentation can be found on Micrel’s web site at www.micrel.com. Typical Applications Dropout vs. Output Current 350 300 MIC37100 IN OUT GND 2.5V DROPOUT (mV) VIN 3.3V 10µF ceramic 2.5V/1A Regulator 2.5VOUT 250 200 150 3.3VOUT 100 50 0 0 0.25 0.5 0.75 OUTPUT CURRENT (A) 1 Super βeta PNP is a registered trademark of Micrel, Inc. PowerPC is a trademark of IBM Corporation. Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com September 2004 1 M9999-091604 MIC37100/37101/37102 Micrel Ordering Information Part Number Voltage Junction Temp. Range Package MIC37100-1.5BS 1.5V –40°C to +125°C SOT-223 MIC37100-1.65BS 1.65V –40°C to +125°C SOT-223 MIC37100-1.8BS 1.8V –40°C to +125°C SOT-223 MIC37100-2.5BS 2.5V –40°C to +125°C SOT-223 MIC37100-3.3BS 3.3V –40°C to +125°C SOT-223 MIC37101-1.5BM 1.5V –40°C to +125°C SOIC-8 MIC37101-1.65BM 1.65V –40°C to +125°C SOIC-8 MIC37101-1.8BM 1.8V –40°C to +125°C SOIC-8 MIC37101-2.5BM 2.5V –40°C to +125°C SOIC-8 MIC37101-3.3BM 3.3V –40°C to +125°C SOIC-8 MIC37102BM Adj. –40°C to +125°C SOIC-8 MIC37101-1.5YM 1.5V –40°C to +125°C SOIC-8 Lead Free MIC37101-1.65YM 1.65V –40°C to +125°C SOIC-8 Lead Free MIC37101-1.8YM 1.8V –40°C to +125°C SOIC-8 Lead Free MIC37101-2.5YM 2.5V –40°C to +125°C SOIC-8 Lead Free MIC37101-3.3YM 3.3V –40°C to +125°C SOIC-8 Lead Free MIC37102YM Adj. –40°C to +125°C SOIC-8 Lead Free MIC37102BR Adj. –40°C to +125°C S-PAK-5 Pin Configuration GND TAB TAB 5 4 3 2 1 1 IN 2 3 GND OUT MIC37100-x.x (Fixed) SOT-223 (S) MIC37102 (Adjustable) S-PAK-5 (R) EN 1 8 GND EN 1 8 GND IN 2 7 GND IN 2 7 GND OUT 3 6 GND OUT 3 6 GND FLG 4 5 GND ADJ 4 5 GND MIC37101-x.x (Fixed) SOIC-8 (M) M9999-091604 ADJ OUT GND IN EN MIC37102 (Adjustable) SOIC-8 (M) 2 September 2004 MIC37100/37101/37102 Micrel Pin Description Pin No. MIC37100 SOT-223 Pin No. MIC37101 SOIC-8 Pin No. MIC37102 SOIC-8 Pin No. MIC37102 S-PAK Pin Name 1 1 1 1 EN Enable (Input): CMOS-compatible control input. Logic high = enable, logic low or open = shutdown. 2 2 2 IN Supply (Input). 3 3 4 OUT Regulator Output. FLG Flag (Output): Open-collector error flag output. Active low = output under voltage. 3 4 2, TAB 5–8 September 2004 Pin Function 4 5 ADJ Adjustment Input: Feedback input. Connect to resistive voltage-divider network. 5–8 3, TAB GND Ground. 3 M9999-091604 MIC37100/37101/37102 Micrel Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VIN) ........................................ 0V to +6.5V Enable Voltage (VEN) ................................................. +6.5V Storage Temperature (TS) ....................... –65°C to +150°C Lead Temperature (soldering, 5 sec.) ....................... 260°C ESD ................................................................................ (3) Supply Voltage (VIN) .................................... +2.25V to +6V Enable Voltage (VEN) .......................................... 0V to +6V Maximum Power Dissipation (P ) ........................... (4) D(max) Junction Temperature (TJ) ....................... –40°C to +125°C Package Thermal Resistance SOT-223 (θJC) ..................................................... 15°C/W SOIC-8 (θJC) ....................................................... 20°C/W S-PAK-5 (θJC) ....................................................... 2°C/W Electrical Characteristics VIN = VOUT + 1V; VEN = 2.25V; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; unless noted Symbol Parameter Condition VOUT Output Voltage 10mA 10mA ≤ IOUT ≤ 1A, VOUT + 1V ≤ VIN ≤ 6V Line Regulation IOUT = 10mA, VOUT + 1V ≤ VIN ≤ 6V Load Regulation VIN = VOUT + 1V, 10mA ≤ IOUT ≤ 1A, ∆VOUT/∆T Output Voltage Temp. Coefficient(6) VDO Dropout Voltage(6) IGND IOUT(lim) Min Typ Max Units 1 2 % % 0.06 0.5 % 0.2 1 % –1 –2 40 ppm/°C IOUT = 100mA, ∆VOUT = –1% 125 200 mV IOUT = 500mA, ∆VOUT = –1% 210 350 mV IOUT = 750mA, ∆VOUT = –1% 250 400 mV IOUT = 1A, ∆VOUT = –1% 280 500 mV IOUT = 100mA, VIN = VOUT + 1V 650 mA IOUT = 500mA, VIN = VOUT + 1V 3.5 mA IOUT = 750mA, VIN = VOUT + 1V 6.7 mA IOUT = 1A, VIN = VOUT + 1V 11 25 mA Current Limit VOUT = 0V, VIN = VOUT + 1V 1.6 2.5 A Enable Input Voltage logic low (off) 0.8 V Ground Current(7) Enable Input VEN logic high (on) IEN Enable Input Current VEN = 2.25V 2.25 1 V 10 VEN = 0.8V 30 µA 2 4 µA µA Flag Output IFLG(leak) Output Leakage Current VOH = 6V 0.01 1 2 µA µA VFLG(do) Output Low Voltage VIN = 2.250V, IOL, = 250µA 210 500 mV VFLG Low Threshold % of VOUT High Threshold % of VOUT 93 99.2 Hysteresis M9999-091604 % 1 4 % % September 2004 MIC37100/37101/37102 Symbol Parameter Micrel Condition Min Typ Max Units 1.228 1.215 1.240 1.252 1.265 V V 40 80 120 nA nA MIC37102 Only Reference Voltage Adjust Pin Bias Current Notes: 1. Exceeding the absolute maximum ratings may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. 4. PD(max) = (TJ(max) – TA) ÷ θJA, where θJA depends upon the printed circuit layout. See “Applications Information” section. 5. Output voltage temperature coefficient is ∆VOUT(worst case) ÷ (TJ(max) – TJ(min)) where TJ(max) is +125°C and TJ(min) is –40°C. 6. VDO = VIN – VOUT when VOUT decreases to 98% of its nominal output voltage with VIN = VOUT + 1V. For output voltages below 2.25V, dropout voltage is the input-to-output voltage differential with the minimum input voltage being 2.25V. Minimum input operating voltage is 2.25V. 7. IGND is the quiescent current. IIN = IGND + IOUT. 8. VEN ≤ 0.8V, VIN ≤ 6V, and VOUT = 0V. September 2004 5 M9999-091604 MIC37100/37101/37102 Micrel Typical Characteristics Power Supply Rejection Ratio Power Supply Rejection Ratio 80 80 VIN = 5V VOUT = 3.3V 70 30 50 40 30 IOUT = 1000mA COUT = 10µF 10 C = 0 IN IOUT = 1000mA COUT = 47µF 10 C = 0 IN 0 0.01 0.1 1 10 100 FREQUENCY (KHz) 20 0.1 1 10 100 FREQUENCY (KHz) 1000 40 30 IOUT = 1000mA COUT = 47µF 10 C = 0 IN 20 250 200 3.3VOUT 150 100 0 0.1 1 10 100 FREQUENCY (KHz) 1000 0 OUTPUT VOLTAGE (V) 150 0.25 0.5 0.75 OUTPUT CURRENT (A) 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 1 Dropout Characteristics (2.5V) 3.0 1000mA Load 0.6 0.4 0.2 1.7 1.9 2.1 2.3 INPUT VOLTAGE (V) 1.2 1.0 0.4 0.2 0.0 1.5 2.5 1000mA Load 0.8 0.6 1.7 1.9 2.1 2.3 2.5 INPUT VOLTAGE (V) GROUND CURRENT (mA) 2.0 1000mA Load 1.0 0.5 4 1000mA Load 1.0 0.5 2 2.5 3 INPUT VOLTAGE (V) 3.5 0.8 10 8 6 4 1.5V OUT 3.3VOUT 2 0 2 2.5 3 3.5 INPUT VOLTAGE (V) 1.5 Ground Current vs. Supply Voltage (1.5V) 12 2.5 2.0 Ground Current vs. Output Current 3.5 10mA Load 10mA Load 2.5 0 1.5 2.7 GROUND CURRENT (mA) OUTPUT VOLTAGE (V) 200 50 1.6 1.4 Dropout Characteristics (3.3V) OUTPUT VOLTAGE (V) 2.5VOUT 250 2.0 10mA Load 1.8 1 M9999-091604 300 Dropout Characteristics (1.8V) 1.2 0 1.5 350 100 10mA Load 1.5 400 50 1.4 3.0 1000 450 Dropout Characteristics (1.5V) 0 1.5 0.1 1 10 100 FREQUENCY (KHz) Dropout vs. Temperature DROPOUT (mV) DROPOUT (mV) PSRR (dB) 50 0.8 0 0.01 1000 2.5VOUT 300 60 0 0.01 30 20 350 VIN = 3.3V VOUT = 2.5V 70 40 Dropout vs. Output Current Power Supply Rejection Ratio 80 50 IOUT = 1000mA COUT = 10µF 10 C = 0 IN 20 OUTPUT VOLTAGE (V) 0 0.01 60 PSRR (dB) PSRR (dB) PSRR (dB) 40 VIN = 3.3V VOUT = 2.5V 70 60 50 1.6 80 VIN = 5V VOUT = 3.3V 70 60 Power Supply Rejection Ratio 0 0.25 0.5 0.75 OUTPUT CURRENT (A) 6 1 0.7 0.6 100mA 0.5 0.4 0.3 0.2 10mA 0.1 0 0 1 2 3 4 5 INPUT VOLTAGE (V) 6 September 2004 MIC37100/37101/37102 Micrel Ground Current vs. Supply Voltage (1.5V) Ground Current vs. Supply Voltage (1.8V) 0.8 14 12 1000mA 10 8 6 4 750mA 2 1 2 3 4 5 INPUT VOLTAGE (V) 0.6 100mA 0.5 0.4 0.3 0.2 10mA 0.1 0 6 0 Ground Current vs. Supply Voltage (2.5V) 100mA 0.6 0.4 10mA 1 2 3 4 5 INPUT VOLTAGE (V) 25 20 15 6 5 750mA GROUND CURRENT (mA) GROUND CURRENT (mA) 25 20 750mA 10 500mA 1 2 3 4 5 INPUT VOLTAGE (V) 6 10 2.5VOUT 6 4 OUTPUT VOLTAGE (V) GROUND CURRENT (mA) 12 1 2 3 4 5 INPUT VOLTAGE (V) 0.4 0.2 5 4.5 4 0.3 2.5VOUT 0.2 0.15 0.1 0.05 IOUT=10mA 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 2.55 2.5 2.5VOUT 2.45 2.4 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 7 10mA 1 2 3 4 5 INPUT VOLTAGE (V) 6 Ground Current vs. Temperature 0.4 0.25 100mA 0.6 0 0 6 IOUT=1000mA 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) September 2004 0 2.6 14 6 1 0.8 3.5 3 2.5 2 2.5VOUT 1.5 1 0.5 IOUT=500mA 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) Output Voltage vs. Temperature 16 2 1 2 3 4 5 INPUT VOLTAGE (V) 1.2 0.35 Ground Current vs. Temperature 8 750mA Ground Current vs. Temperature Ground Current vs. Supply Voltage (3.3V) 5 1000mA 10 0 30 15 5 1.4 GROUND CURRENT (mA) 0.2 1000mA 10 Ground Current vs. Supply Voltage (3.3V) GROUND CURRENT (mA) GROUND CURRENT (mA) GROUND CURRENT (mA) 1 0 0 6 30 1.2 0.8 15 Ground Current vs. Supply Voltage (2.5V) 1.4 0 0 1 2 3 4 5 INPUT VOLTAGE (V) 20 0 0 Short Circuit Current vs. Supply Voltage SHORT CIRCUIT CURRENT (A) 0 0 25 0.7 GROUND CURRENT (mA) 16 GROUND CURRENT (mA) GROUND CURRENT (mA) 18 Ground Current vs. Supply Voltage (1.8V) 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 2.25 3 3.75 4.5 5.25 SUPPLY VOLTAGE (V) 6 M9999-091604 MIC37100/37101/37102 Micrel 1.4 2.5VIN 1.2 1.0 0.8 0.6 0.4 0.8 3.3VIN 0.6 5VIN 2.5VIN 0.4 0.2 0.2 0 0 0.5 1 1.5 2 2.5 3 3.5 4 FLAG CURRENT (mA) 0.0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 5 4 3 2 Flag Low (FAULT) 1 0 0.01 0.1 1 10 100 1000 10000 RESISTANCE (kΩ) M9999-091604 250 200 150 100 50 Flag Current = 250µA 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 9 VIN=5V ENABLE CURRENT (µA) Flag High (OK) 300 Enable Current vs. Temperature Error Flag Pull-Up Resistor 6 FLAG LOW VOLTAGE (mV) 350 1.6 FLAG VOLTAGE (V) SHORT CIRCUIT CURRENT (A) 1.0 1.8 FLAG VOLTAGE (V) Flag Low Voltage vs. Temperature Flag Voltage vs. Flag Current Short Circuit Current vs. Temperature 8 7 6 5 4 2.5VEN 3 2 1 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 8 September 2004 MIC37100/37101/37102 Micrel Functional Characteristics Load Transient Response OUTPUT VOLTAGE (200mV/div) OUTPUT VOLTAGE (200mV/div) Load Transient Response VIN = 3.3V VOUT = 2.5V COUT = 10µF Ceramic 100mA Line Transient Response Enable Transient Response ENABLE VOLTAGE (2V/div) TIME (400µs/div.) 5V 3.3V OUTPUT VOLTAGE (1V/div) VOUT = 2.5V COUT = 10µF Ceramic Load=100mA TIME (400µs/div.) September 2004 10mA TIME (400µs/div.) INPUT VOLTAGE (2V/div) OUTPUT VOLTAGE (50mV/div) 1000mA LOAD CURRENT (500mA/div) LOAD CURRENT (500mA/div) 1000mA VIN = 3.3V VOUT = 2.5V COUT = 10µF Ceramic VIN = 3.3V VOUT = 2.5V IOUT = 100mA COUT = 10µF Ceramic TIME (10µs/div.) 9 M9999-091604 MIC37100/37101/37102 Micrel Functional Diagrams OUT IN 1.240V Ref. Thermal Shutdown MIC37100 MIC37100 Fixed Regulator Block Diagram OUT IN 1.180V FLAG Ref. 1.240V EN Thermal Shutdown GND MIC37101 MIC37101 Fixed Regulator with Flag and Enable Block Diagram OUT IN Ref. 1.240V ADJ EN Thermal Shutdown GND MIC37102 MIC37102 Adjustable Regulator Block Diagram M9999-091604 10 September 2004 MIC37100/37101/37102 Micrel Input Capacitor An input capacitor of 1µF or greater is recommended when the device is more than 4 inches away from the bulk ac supply capacitance or when the supply is a battery. Small, surface mount, ceramic chip capacitors can be used for bypassing. Larger values will help to improve ripple rejection by bypassing the input to the regulator, further improving the integrity of the output voltage. Error Flag The MIC37101 features an error flag (FLG), which monitors the output voltage and signals an error condition when this voltage drops 5% below its expected value. The error flag is an open-collector output that pulls low under fault conditions and may sink up to 10mA. Low output voltage signifies a number of possible problems, including an overcurrent fault (the device is in current limit) or low input voltage. The flag output is inoperative during overtemperature conditions. A pull-up resistor from FLG to either VIN or VOUT is required for proper operation. For information regarding the minimum and maximum values of pull-up resistance, refer to the graph in the “Typical Characteristics” section of the data sheet. Enable Input The MIC37101 and MIC37102 versions feature an activehigh enable input (EN) that allows on-off control of the regulator. Current drain reduces to “zero” when the device is shutdown, with only microamperes of leakage current. The EN input has TTL/CMOS compatible thresholds for simple logic interfacing. EN may be directly tied to VIN and pulled up to the maximum supply voltage Transient Response and 3.3V to 2.5V or 2.5V to 1.8V, 1.65V or 1.5V Conversion The MIC37100/01/02 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 10µF output capacitor, is all that is required. Larger values help to improve performance even further. 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 2.5V or 2.5V to 1.8V, or lower, the NPN based regulators are already operating in dropout, with typical dropout requirements of 1.2V or greater. To convert down to 2.5V or 1.8V without operating in dropout, NPN-based regulators require an input voltage of 3.7V at the very least. The MIC37100 regulator will provide excellent performance with an input as low as 3.0V or 2.5V respectively. This gives the PNP based regulators a distinct advantage over older, NPN based linear regulators. Applications Information The MIC37100/01/02 is a high-performance low-dropout voltage regulator suitable for moderate to high-current voltage regulator applications. Its 500mV dropout voltage at full load and overtemperature makes it especially valuable in battery-powered systems and as high-efficiency noise filters in post-regulator applications. Unlike older NPN-pass transistor designs, where the minimum dropout voltage is limited by the base-to-emitter voltage drop and collector-to-emitter saturation voltage, dropout performance of the PNP output of these devices is limited only by the low VCE saturation voltage. A trade-off for the low dropout voltage is a varying base drive requirement. Micrel’s Super βeta PNP™ process reduces this drive requirement to only 2% of the load current. The MIC37100/01/02 regulator is fully protected from damage due to fault conditions. Linear current limiting is provided. Output current during overload conditions is constant. Thermal shutdown disables the device when the die temperature exceeds the maximum safe operating temperature. The output structure of these regulators allows voltages in excess of the desired output voltage to be applied without reverse current flow. VIN MIC37100-x.x IN CIN VOUT OUT GND COUT Figure 1. Capacitor Requirements Output Capacitor The MIC37100/01/02 requires an output capacitor to maintain stability and improve transient response. As a µCap LDO, the MIC37100/01/02 can operate with ceramic output capacitors as long as the amount of capacitance is 10µF or greater. For values of output capacitance lower than 10µF, the recommended ESR range is 200mΩ to 2Ω. The minimum value of output capacitance recommended for the MIC37100/ 01/02 is 4.7µF. For 10µF or greater the ESR range recommended is less than 1Ω. Ultra-low ESR ceramic capacitors are recommended for output capacitance of 10µF 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. X7Rtype 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 with Y5V dielectric, the value must be much higher than an X7R ceramic capacitor to ensure the same minimum capacitance over the equivalent operating temperature range. September 2004 11 M9999-091604 MIC37100/37101/37102 Micrel Minimum Load Current The MIC37100/01/02 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 regulation. Adjustable Regulator Design VIN MIC37102 OUT IN been used by MOSFET manufacturers for years, proving very reliable and cost effective for the user. Thermal resistance consists of two main elements, θJC (junction-to-case thermal resistance) and θCA (case-to-ambient thermal resistance). See Figure 3. θJC is the resistance from the die to the leads of the package. θCA is the resistance from the leads to the ambient air and it includes θCS (case-tosink thermal resistance) and θSA (sink-to-ambient thermal resistance). VOUT R1 ENABLE SHUTDOWN EN ADJ GND R2 COUT SOIC-8 R1 VOUT = 1.240V 1 + R2 Figure 2. Adjustable Regulator with Resistors The MIC37102 allows programming the output voltage anywhere between 1.24V and the 6V maximum operating rating of the family. Two resistors are used. Resistors can be quite large, up to 1MΩ, because of the very high input impedance and low bias current of the sense comparator: The resistor values are calculated by: θJA θJC θCA ground plane heat sink area AMBIENT printed circuit board V R1 = R2 OUT − 1 1.240 Figure 3. Thermal Resistance Using the power SOIC-8 reduces the θJC dramatically and allows the user to reduce θCA. The total thermal resistance, θJA (junction-to-ambient thermal resistance) is the limiting factor in calculating the maximum power dissipation capability of the device. Typically, the power SOIC-8 has a θJC of 20°C/W, this is significantly lower than the standard SOIC-8 which is typically 75°C/W. θCA is reduced because pins 5 through 8 can now be soldered directly to a ground plane which significantly reduces the case-to-sink thermal resistance and sink to ambient thermal resistance. Low-dropout linear regulators from Micrel are rated to a maximum junction temperature of 125°C. It is important not to exceed this maximum junction temperature during operation of the device. To prevent this maximum junction temperature from being exceeded, the appropriate ground plane heat sink must be used. Where VO 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). Power SOIC-8 Thermal Characteristics One of the secrets of the MIC37101/02’s performance is its power SO-8 package featuring half the thermal resistance of a standard SO-8 package. Lower thermal resistance means more output current or higher input voltage for a given package size. Lower thermal resistance is achieved by joining the four ground leads with the die attach paddle to create a singlepiece electrical and thermal conductor. This concept has M9999-091604 12 September 2004 MIC37100/37101/37102 Micrel Using Figure 4, the minimum amount of required copper can be determined based on the required power dissipation. Power dissipation in a linear regulator is calculated as follows: PD = (VIN – VOUT) IOUT + VIN × IGND If we use a 2.5V output device and a 3.3V input at an output current of 1A, then our power dissipation is as follows: PD = (3.3V – 2.5V) × 1A + 3.3V × 11mA PD = 800mW + 36mW 700 ∆TJA = 100°C COPPER AREA (mm2) 800 40°C 50°C 55°C 65°C 75°C 85°C 900 600 500 400 300 200 100 0 0 0.25 0.50 0.75 1.00 1.25 1.50 POWER DISSIPATION (W) PD = 836mW From Figure 4, the minimum amount of copper required to operate this application at a ∆T of 75°C is 160mm2. Quick Method Determine the power dissipation requirements for the design along with the maximum ambient temperature at which the device will be operated. Refer to Figure 5, which shows safe operating curves for three different ambient temperatures: 25°C, 50°C and 85°C. From these curves, the minimum amount of copper can be determined by knowing the maximum power dissipation required. If the maximum ambient temperature is 50°C and the power dissipation is as above, 836mW, the curve in Figure 5 shows that the required area of copper is 160mm2. The θJA of this package is ideally 63°C/W, but it will vary depending upon the availability of copper ground plane to which it is attached. Figure 4. Copper Area vs. Power SO-8 Power Dissipation Figure 4 shows copper area versus power dissipation with each trace corresponding to a different temperature rise above ambient. From these curves, the minimum area of copper necessary for the part to operate safely can be determined. The maximum allowable temperature rise must be calculated to determine operation along which curve. ∆T = TJ(max) – TA(max) TJ(max) = 125°C TA(max) = maximum ambient operating temperature For example, the maximum ambient temperature is 50°C, the ∆T is determined as follows: ∆T = 125°C – 50°C ∆T = 75°C COPPER AREA (mm2) 900 800 TJ = 125°C 700 TA = 85°C 50°C 25°C 600 500 400 300 200 100 0 0 0.25 0.50 0.75 1.00 1.25 1.50 POWER DISSIPATION (W) Figure 5. Copper Area vs. Power-SOIC Power Dissipation September 2004 13 M9999-091604 MIC37100/37101/37102 Micrel Package Information 3.15 (0.124) 2.90 (0.114) CL 3.71 (0.146) 7.49 (0.295) 3.30 (0.130) 6.71 (0.264) CL 2.41 (0.095) 2.21 (0.087) 1.04 (0.041) 0.85 (0.033) 4.7 (0.185) 4.5 (0.177) 0.10 (0.004) 0.02 (0.0008) DIMENSIONS: MM (INCH) 6.70 (0.264) 6.30 (0.248) 1.70 (0.067) 16° 1.52 (0.060) 10° 10° MAX 0.38 (0.015) 0.25 (0.010) 0.84 (0.033) 0.64 (0.025) 0.91 (0.036) MIN SOT-223 (S) 0.026 (0.65) MAX) PIN 1 0.157 (3.99) 0.150 (3.81) DIMENSIONS: INCHES (MM) 0.050 (1.27) TYP 0.064 (1.63) 0.045 (1.14) 0.197 (5.0) 0.189 (4.8) 0.020 (0.51) 0.013 (0.33) 0.0098 (0.249) 0.0040 (0.102) 0°–8° SEATING PLANE 45° 0.010 (0.25) 0.007 (0.18) 0.050 (1.27) 0.016 (0.40) 0.244 (6.20) 0.228 (5.79) 8-Lead SOIC (M) M9999-091604 14 September 2004 MIC37100/37101/37102 Micrel DIMENSIONS: INCH (MM) 0.375 (9.52) 0.365 (9.27) 0.360 (9.14) 0.350 (8.89) 0.050 (1.27) 0.030 (0.76) 0.080 (2.03) 0.070 (1.78) 0.256 BSC (6.50 BSC) 0.010 BSC (0.25 BSC) 0.045 (1.14) 0.035 (0.89) 0.316 BSC (8.03 BSC) 0.420 (10.67) 0.410 (10.41) 0.320 (8.13) 0.310 (7.87) 0.067 BSC (1.70 BSC) 0.031 (0.79) 0.025 (0.63) 0.005 (0.13) 0.001 (0.03) 0.080 (2.03) 0.070 (1.78) 0.031 (0.89) 0.041 (1.14) 0.010 BSC (0.25 BSC) 6¡ 0¡ 5 Lead S-PAK (R) MICREL, INC. TEL 1849 FORTUNE DRIVE SAN JOSE, CA 95131 + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB USA 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 at Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2004 Micrel, Incorporated. September 2004 15 M9999-091604