MIC3975 Micrel MIC3975 750mA µCap Low-Voltage Low-Dropout Regulator General Description Features The MIC3975 is a 750mA low-dropout 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 MIC3975 offers extremely low dropout (typically 300mV at 750mA) and low ground current (typically 6.5mA at 750mA). The MIC3975 is ideal for PC add-in cards that need to convert from standard 5V to 3.3V or 3.0V, 3.3V to 2.5V or 2.5V to 1.8V or 1.65V. A guaranteed maximum dropout voltage of 500mV over all operating conditions allows the MIC3975 to provide 2.5V from a supply as low as 3.0V and 1.8V or 1.65V from a supply as low as 2.25V. • Fixed and adjustable output voltages to 1.24V • 300mV typical dropout at 750mA Ideal for 3.0V to 2.5V conversion Ideal for 2.5V to 1.8V or 1.65V conversion • Stable with ceramic capacitor • 750mA minimum guaranteed output current • 1% initial accuracy • Low ground current • Current limiting and thermal shutdown • Reversed-battery protection • Reversed-leakage protection • Fast transient response • Low-profile MSOP-8 The MIC3975 is fully protected with overcurrent limiting, thermal shutdown, and reversed-battery protection. Fixed voltages of 5.0V, 3.3V, 3.0, 2.5V, 1.8V, and 1.65V are available. An adjustable output voltage option is available for voltages down to 1.24V. For other voltages, contact Micrel. Applications • • • • • • • • Fiber optic modules 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 Ordering Information Part Number Standard Pb-Free Voltage Junction Temp. Range Package MIC3975-1.65BMM MIC3975-1.65YMM 1.65V –40°C to +125°C MSOP-8 MIC3975-1.8BMM MIC3975-1.8YMM 1.8V –40°C to +125°C MSOP-8 MIC3975-2.5BMM MIC3975-2.5YMM 2.5V –40°C to +125°C MSOP-8 MIC3975-3.0BMM MIC3975-3.0YMM 3.0V –40°C to +125°C MSOP-8 MIC3975-3.3BMM MIC3975-3.3YMM 3.3V –40°C to +125°C MSOP-8 MIC3975-5.0BMM MIC3975-5.0YMM 5.0V –40°C to +125°C MSOP-8 MIC3975BMM MIC3975YMM Adj. –40°C to +125°C MSOP-8 Typical Applications 100k VIN 3.3V ENABLE SHUTDOWN MIC3975-2.5BMM OUT IN EN FLG GND Error Flag Output R1 VIN 2.5V 2.5V ENABLE SHUTDOWN 10F ceramic MIC3975BMM OUT IN EN ADJ GND R1 R2 1.5V 10F ceramic 1.5V/750mA Adjustable Regulator 2.5V/750mA Regulator with Error Flag Super βeta PNP is a 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 February 2005 1 MIC3975 MIC3975 Micrel Pin Configuration EN 1 8 GND EN 1 8 GND IN 2 7 GND IN 2 7 GND FLG 3 6 GND ADJ 3 6 GND OUT 4 5 GND OUT 4 5 GND Adjustable MIC3975-x.x Fixed MSOP-8 (MM) Pin Description Pin No. Pin No. Fixed Adjustable 1 1 2 2 3 3 Pin Name EN IN Pin Function Enable (Input): CMOS-compatible control input. Logic high = enable, logic low or open = shutdown. Supply (Input) FLG Flag (Output): Open-collector error flag output. Active low = output undervoltage. ADJ Adjustment Input: Feedback input. Connect to resistive voltage-divider network. 4 4 OUT Regulator Output 5–8 5–8 GND Ground MIC3975 2 February 2005 MIC3975 Micrel Absolute Maximum Ratings (Note 1) Operating Ratings (Note 2) Supply Voltage (VIN) .......................................–20V to +20V Enable Voltage (VEN) .................................................. +20V Storage Temperature (TS) ........................ –65°C to +150°C Lead Temperature (soldering, 5 sec.) ........................ 260°C ESD, Note 3 Supply Voltage (VIN) ................................... +2.25V to +16V Enable Voltage (VEN) .................................................. +16V Maximum Power Dissipation (PD(max)) ..................... Note 4 Junction Temperature (TJ) ........................ –40°C to +125°C Package Thermal Resistance MSOP-8 (θJA) ...................................................... 80°C/W Electrical Characteristics(Note 12) 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 ≤ 750mA, VOUT + 1V ≤ VIN ≤ 8V Line Regulation Load Regulation ΔVOUT/ΔT ppm/°C VDO Output Voltage Temp. Coefficient, Min Typ –1 –2 IOUT = 10mA, VOUT + 1V ≤ VIN ≤ 16V Max Units 1 2 % % 0.06 0.5 % VIN = VOUT + 1V, 10mA ≤ IOUT ≤ 750mA, 0.2 1 % 40 100 IOUT = 100mA, ΔVOUT = –1% 140 200 250 mV mV IOUT = 500mA, ΔVOUT = –1% 225 500 mV IOUT = 100mA, VIN = VOUT + 1V 400 µA 4 mA IOUT = 750mA, VIN = VOUT + 1V 7.5 15 mA 1.8 2.5 A 0.8 V 30 75 µA µA 2 4 µA µA Note 5 Dropout Voltage, Note 6 IOUT = 750mA, ΔVOUT = –1% IGND Ground Current, Note 7 IOUT(lim) Current Limit VOUT = 0V, VIN = VOUT + 1V VEN Enable Input Voltage logic low (off) IEN Enable Input Current VEN = 2.25V 300 IOUT = 500mA, VIN = VOUT + 1V Enable Input logic high (on) mV 2.25 1 V 15 VEN = 0.8V Flag Output IFLG(leak) Output Leakage Current VOH = 16V 0.01 1 2 µA µA VFLG(do) Output Low Voltage VIN = 2.250V, IOL, = 250µA, Note 9 210 300 400 mV mV VFLG Low Threshold % of VOUT High Threshold Hysteresis February 2005 93 % of VOUT % 99.2 1 3 % % MIC3975 MIC3975 Symbol Micrel Parameter Condition Min Typ Max Units 1.228 1.215 1.203 1.240 1.252 1.265 1.277 V V V 40 80 120 nA nA Adjustable Output Only Reference Voltage Note 10 Adjust Pin Bias Current Reference Voltage ppm/°C Note 11 20 Temp. Coefficient Adjust Pin Bias Current Temp. Coefficient 0.1 Note 1. Exceeding the absolute maximum ratings may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note 3. Devices are ESD sensitive. Handling precautions recommended. Note 4. PD(max) = (TJ(max) – TA) ÷ θJA, where θJA depends upon the printed circuit layout. See “Applications Information.” Note 5. Note 6. Note 7. Note 8. Note 9. nA/°C Output voltage temperature coefficient is ΔVOUT(worst case) ÷ (TJ(max) – TJ(min)) where TJ(max) is +125°C and TJ(min) is –40°C. 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. IGND is the quiescent current. IIN = IGND + IOUT. VEN ≤ 0.8V, VIN ≤ 8V, and VOUT = 0V. For a 2.5V device, VIN = 2.250V (device is in dropout). Note 10. VREF ≤ VOUT ≤ (VIN – 1V), 2.25V ≤ VIN ≤ 16V, 10mA ≤ IL ≤ 750mA, TJ = TMAX. Note 11. 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 200mA load pulse at VIN = 16V for t = 10ms. Note 12. Specification for packaged product only. MIC3975 4 February 2005 MIC3975 Micrel Typical Characteristics February 2005 5 MIC3975 MIC3975 MIC3975 Micrel 6 February 2005 MIC3975 Micrel Functional Characteristics OUTPUT VOLTAGE (200mV/div.) Load Transient Response VIN = 3.3V VOUT = 2.5V COUT = 10F Ceramic VIN = 3.3V VOUT = 2.5V COUT = 10F Ceramic 750mA LOAD CURRENT (500mA/div.) 750mA LOAD CURRENT (500mA/div.) OUTPUT VOLTAGE (200mV/div.) Load Transient Response 100mA 10mA TIME (200s/div.) TIME (200s/div.) Line Transient Response OUTPUT VOLTAGE (50mV/div.) INPUT VOLTAGE (1V/div.) 5.0V 3.3V VOUT = 2.5V COUT = 10F Ceramic ILOAD = 10mA TIME (200s/div.) February 2005 7 MIC3975 MIC3975 Micrel Functional Diagrams OUT IN O.V. ILIMIT 1.180V FLAG Ref. 18V 1.240V EN Thermal Shutdown GND MIC3975 Fixed Regulator with Flag and Enable Block Diagram OUT IN O.V. ILIMIT Ref. 18V 1.240V ADJ EN Thermal Shutdown GND MIC3975 Adjustable Regulator Block Diagram MIC3975 8 February 2005 MIC3975 Micrel Applications Information 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 MIC3975 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 MIC3975 features an active-high 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 or 1.65V Conversion The MIC3975 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 1.65V, 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 MIC3975 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. Minimum Load Current The MIC3975 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. The MIC3975 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 MIC3975 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. 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. VIN CIN MIC3975x.x IN OUT GND VOUT COUT Figure 1. Capacitor Requirements Output Capacitor The MIC3975 requires an output capacitor for stable operation. As a µCap LDO, the MIC3975 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 MIC3975 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. 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 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. February 2005 9 MIC3975 MIC3975 Micrel Adjustable Regulator Design VIN ENABLE SHUTDOWN MIC3975 OUT IN EN ADJ GND R1 R2 Using the power MSOP-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 MSOP-8 has a θJA of 80°C/W, this is significantly lower than the standard MSOP-8 which is typically 160°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. VOUT COUT R1 VOUT 1.240V 1 R2 Figure 2. Adjustable Regulator with Resistors The MIC3975 allows programming the output voltage anywhere between 1.24V and the 16V 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: V R1 R2 OUT 1 1.240 MSOP-8 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 MSOP-8 Thermal Characteristics One of the secrets of the MIC3975’s performance is its power MSO-8 package featuring half the thermal resistance of a standard MSO-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 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 (caseto-sink thermal resistance) and θSA (sink-to-ambient thermal resistance). JA JC AMBIENT printed circuit board Figure 3. Thermal Resistance 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. ΔT = TJ(max) – TA(max) TJ(max) = 125°C Figure 4. Copper Area vs. Power-MSOP Power Dissipation (∆TJA) MIC3975 ground plane heat sink area CA Figure 5. Copper Area vs. Power-MSOP Power Dissipation (TA) 10 February 2005 MIC3975 Micrel TA(max) = maximum ambient operating temperature For example, the maximum ambient temperature is 50°C, the ΔT is determined as follows: ΔT = 125°C – 50°C ΔT = 75°C 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 750mA, then our power dissipation is as follows: PD = (3.3V – 2.5V) × 750mA + 3.3V × 7.5mA PD = 600mW + 25mW PD = 625mW From Figure 4, the minimum amount of copper required to operate this application at a ΔT of 75°C is 160mm2. 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, 625mW, the curve in Figure 5 shows that the required area of copper is 160mm2. The θJA of this package is ideally 80°C/W, but it will vary depending upon the availability of copper ground plane to which it is attached. 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 February 2005 11 MIC3975 MIC3975 Micrel Package Information 8-Lead MSOP (MM) MICREL, INC. TEL 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com The information furnished by Micrel in this datasheet 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 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. © 2005 Micrel, Incorporated. MIC3975 12 February 2005