19-2528; Rev 1; 2/03 KIT ATION EVALU E L B A AVAIL Wide-Input 0.6V Shunt Regulators for Isolated DC-to-DC Converters Features ♦ MAX8515A 0.6V ±0.5% Initial Accuracy at +25°C 0.6V ±1% Accuracy from -40°C to +85°C The MAX8515A features an initial output accuracy of 0.5% at +25°C and 1% from -40°C to +85°C and provides the output voltage regulation function for isolated DC-toDC converters. The MAX8515 features initial output accuracy of 1% at +25°C and 1.8% from -40°C to +85°C and can provide an output OVP function for isolated DCto-DC converters. High open-loop bandwidth allows design of high-bandwidth DC-to-DC converters. ♦ Space-Saving 5-Pin SC70 or SOT23 Packages Low-cost, low-dropout linear regulators can be designed with the MAX8515A/MAX8515 and an external NPN transistor for cost-conscious applications that do not require overcurrent, short-circuit, or overtemperature protection. The MAX8515/MAX8515A are available in space-saving 5-pin SC70 and SOT23 packages and are specified over the -40°C to +85°C extended temperature range. An evaluation kit is available to speed designs. Applications ♦ MAX8515 0.6V ±1% Initial Accuracy at +25°C 0.6V ±1.8% Accuracy from -40°C to +85°C ♦ Sinks 20mA at 0.2V to 18V ♦ Input Voltage Range from 1.7V to 28V ♦ Directly Drives Optocouplers ♦ 0.2Ω Dynamic Output Impedance Ordering Information PART TEMP RANGE PIN-PACKAGE MAX8515AEXK-T -40°C to +85°C 5 SC70-5 MAX8515AEZK-T -40°C to +85°C 5 Thin SOT23-5 MAX8515EXK-T -40°C to +85°C 5 SC70-5 MAX8515EZK-T -40°C to +85°C 5 Thin SOT23-5 Functional Diagram appears at end of data sheet. Selector Guide appears at end of data sheet. Isolated DC-to-DC Converters Network, Telecom, and Cellular Base Station Power Supplies Typical Operating Circuit Low-Dropout Linear Regulators INPUT SUPPLY INPUT 1.7V TO 28V 1.7V TO 18V Shunt Regulator Adjustable Voltage Reference PRIMARY SIDE PWM CONVERTER CONTROL VOLTAGE Pin Configuration TOP VIEW IN FB 5 MAX8515A MAX8515 N SC7 -PI 2.0 m OUT 3 4 IN 0 GND 2 5 mm PGND 1 m x 2.1 MAX8515A MAX8515 PGND GND OUT FB ISOLATED DC-DC CONVERTER OUTPUT (DOWN TO 0.6V) SC7O/THIN SOT23 ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX8515A/MAX8515 General Description The MAX8515A/MAX8515 shunt regulators simplify the design of voltage regulation and overvoltage protection (OVP) functions in high-accuracy isolated DC-to-DC converters with output voltages as low as 0.6V. The devices have supply voltage and feedback inputs separated from the output shunt stage, and can operate directly from the DC-to-DC converter output stage when the output voltage is 1.8V to 18V. Alternately, the MAX8515A/MAX8515 input stage can be biased from an unregulated 1.7V to 28V supply, independent of DC-to-DC converter output voltage. The MAX8515A/MAX8515 shunts 20mA when the output voltage is as low as 0.2V. MAX8515A/MAX8515 Wide-Input 0.6V Shunt Regulators for Isolated DC-to-DC Converters ABSOLUTE MAXIMUM RATINGS IN to GND ...............................................................-0.3V to +30V OUT to GND ...........................................................-0.3V to +20V FB to GND .................-0.3V to the lower of 5.5V and (VIN +0.3V) PGND to GND .......................................................-0.3V to +0.3V Continuous Power Dissipation (TA =+70°C) 5-Pin SC70 (derate 3.1mW/°C above +70°C) ...........246.9mW 5-Pin Thin SOT23 (derate 9.1mW/°C above +70°C) ....727mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature Range ............................-40°C to +150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN = 3.3V, OUT = FB, IOUT = 5mA, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 28 V IN IN Voltage Range IN Supply Current VIN IIN 1.7 VIN = 2V to 28V IOUT = 0.3mA 0.5 1 IOUT = 10mA 2.5 4 mA FB TA = +25°C FB Threshold Accuracy TA = 0°C to +85°C TA = -40°C to +85°C FB Load Regulation FB Line Regulation 0.597 0.6 0.603 MAX8515E_K 0.594 0.6 0.606 MAX8515AE_K 0.595 0.6 0.605 MAX8515E_K 0.592 0.6 0.608 MAX8515AE_K 0.594 0.6 0.606 MAX8515E_K 0.589 0.6 0.608 IOUT = 1mA to 20mA 3.8 6 VIN = 2V to 28V 0.2 1 VIN = 1.7V to 28V FB Output Voltage Regulation FB Input Bias Current MAX8515AE_K 1.5 VOUT = 0.2V to 18V, IOUT = 1mA IFB(BIAS) VIN = 28V -0.1 V mV mV 0.2 1 mV 0.02 +0.1 µA OUT OUT Voltage Range VOUT 0.2 Maximum Output Current IOUT(MAX) VOUT = 0.2V, VIN = 2V, VFB = 0.63V Output Leakage Current IOUT(LEAK) Dynamic Output Impedance ZOUT VIN = 28V, VOUT = 18V, VFB = 0V 18 20 TA = +25°C 0.001 TA = +85°C 0.03 IOUT = 1mA to 20mA, f <1kHz 0.2 Note 1: Devices are production tested at TA = +25°C, limits over temperature are guaranteed by design. 2 V mA _______________________________________________________________________________________ 0.1 0.32 µA Ω Wide-Input 0.6V Shunt Regulators for Isolated DC-to-DC Converters 35 OUT-LEAKAGE CURRENT (nA) VIN = 10V -15 -20 VIN = 28V -25 -30 30 10 40 20 15 10 35 60 20 -45 10 5 -10 0 -20 85 0 30 -90 0 -135 FIGURE 2 -30 -40 -15 TEMPERATURE (°C) 10 35 60 0.1 85 1 MAX8515 toc04 40 30 10 MAX8515 toc05 VOUT: 2V/div -45 0 -90 1 10 C2 = OPEN -180 1000 -30 0.1 0.66V 0.55V VFB: 200mV/div -135 FIGURE 2 -20 PHASE (DEGREES) 0 10 -10 100 -180 1000 OUTPUT VOLTAGE SLEW RATE 90 45 20 100 FREQUENCY (kHz) TEMPERATURE (°C) GAIN AND PHASE vs. FREQUENCY VOUT = 6V GAIN (dB) 2µs/div FREQUENCY (kHz) POWER-SUPPLY REJECTION RATIO vs. FREQUENCY TA = +25°C 0 TA = +85°C -20 -30 -40 -50 TA = +25°C -60 -70 -80 1 10 100 FREQUENCY (Hz) 3.0 2.5 VIN = 10V 2.0 1.5 VIN = 28V 1.0 0.5 TA = -40°C 0.1 VIN = 3.3V 3.5 SUPPLY CURRENT (mA) -10 SUPPLY CURRENT vs. LOAD CURRENT 4.0 MAX8515 toc07 10 MAX8515 toc06 -15 45 50 25 -5 -40 PSRR (dB) FB BIAS CURRENT (nA) VIN = 3.3V 70 60 GAIN (dB) -5 VIN = 28V VOUT = 18V FB = GND MAX8515 toc03 70 MAX8515 toc02 40 MAX8515 toc01 0 -10 GAIN AND PHASE vs. FREQUENCY VOUT = 0.6V OUT-LEAKAGE CURRENT vs. TEMPERATURE PHASE (DEGREES) FB BIAS CURRENT vs. TEMPERATURE 1k 10k 0 0 5 10 15 20 LOAD CURRENT (mA) _______________________________________________________________________________________ 3 MAX8515A/MAX8515 Typical Operating Characteristics (VIN = 3.3V, IOUT = 5mA, FB = OUT, circuit in Figure 1, C1 = 0.1µF, C2 = 1µF, TA = +25°C, unless otherwise specified.) Typical Operating Characteristics (continued) (VIN = 3.3V, IOUT = 5mA, FB = OUT, circuit in Figure 1, C1 = 0.1µF, C2 = 1µF, TA = +25°C, unless otherwise specified.) OUTPUT VOLTAGE CHANGE vs. INPUT VOLTAGE OUTPUT VOLTAGE CHANGE vs. LOAD CURRENT 0.4 OUTPUT VOLTAGE CHANGE (%) 0.5 0.3 0.2 0.1 0 -0.1 MAX8515 toc09 0.05 MAX8515 toc08 0.6 OUTPUT VOLTAGE CHANGE (%) MAX8515A/MAX8515 Wide-Input 0.6V Shunt Regulators for Isolated DC-to-DC Converters 0.04 0.03 0.02 0.01 0 -0.2 -0.3 -0.01 0 5 10 15 3 20 8 13 18 23 28 INPUT VOLTAGE (V) LOAD CURRENT (mA) Pin Description PIN NAME FUNCTION 1 PGND Power Ground. Connect PGND and GND together. 2 GND Analog Ground. Connect GND and PGND together. 3 OUT Output. Connect a ceramic capacitor from OUT to GND. See the Applications Information section. 4 IN Supply Input. Connect a 0.1µF capacitor to GND. 5 FB Feedback Input. Regulates to 600mV. Detailed Description The MAX8515A/MAX8515 adjustable shunt regulators feature isolated supply inputs and outputs, ideal for isolated power-supply applications using an optocoupler in the feedback path. The MAX8515A/MAX8515 sink 20mA with VOUT at 0.2V. The wide input supply range allows the device to operate from 1.7V to 28V. The MAX8515A/ MAX8515 compare the FB input to a precision 600mV reference. If the FB input is low, OUT sinks no current. If FB rises above 600mV, OUT sinks up to 20mA. Applications Information Shunt Regulator/Adjustable Voltage Reference Figure 1 shows the MAX8515A/MAX8515 configured as a shunt regulator. Connect FB to OUT for an output voltage of 0.6V. Connect a 1.0µF capacitor from OUT to GND 4 when the output voltage is 0.6V. A resistor-divider connected from OUT to GND produces higher output voltages and allows for a smaller output capacitor. The value of the output capacitor is inversely proportional to the output voltage: R1 VOUT = 0.6 × 1 + R2 0.6 COUT = 1µF × VOUT Set the current limit with a resistor connected from IN to OUT. This type of shunt regulator is limited to low-current applications. The MAX8515A/MAX8515 can typically sink up to 20mA in this application. Figure 2 shows the test circuits for gain and phase plots. _______________________________________________________________________________________ Wide-Input 0.6V Shunt Regulators for Isolated DC-to-DC Converters MAX8515A/MAX8515 5.6V VIN 1.8V R3 IN C1 0.1µF 1kΩ R1 C2 1.0µF PGND FB R2 IN VIN (V) R3 (Ω) 135 3.3 470 10 1.33k 28 TEST 2.2nF VOUT = 0.6V TEST CIRCUIT R1 = SHORT R2 = OPEN OUT MAX8515A MAX8515 GND 3.3V VOUT 0.6V/20mA 1MΩ OUT 0.82µF 0.1µF MAX8515A MAX8515 50kΩ PGND GND NETWORK ANALYZER SOURCE FB 2.2nF REFERENCE 1MΩ Figure 1. MAX8515A/MAX8515 Typical Application Circuit, Shunt Regulator/Adjustable Voltage Reference GAIN = TEST/REFERENCE 11V Optical Feedback Setting VOUT Figure 3 displays an application circuit using the MAX8515A/MAX8515 in an opto-isolated feedback circuit. The maximum bias current for the photodiode is set with R1. The isolated DC-to-DC converter compensation circuit is formed with R2, C3, and C4. Resistors R3 and R4 set the isolated DC-to-DC converter output voltage. C1 decouples the input supply and C2 is needed to stabilize the MAX8515A/MAX8515. Calculate VREG with the following equation: R3 VREG = 0.6 × 1 + R4 115kΩ 1% 3.3V VOUT = 6V TEST CIRCUIT IN For example, given a regulator output voltage of 1.8V and R4 = 10kΩ, R3 is found to be 20kΩ. Compensation Circuit A typical compensation scheme is depicted in Figure 3. C3 provides an integrator function that minimizes output regulation error. R2 provides additional phase compensation at the zero frequency fz: 1 fZ = 2π × R2 × C3 1MΩ 160kΩ OUT 0.1µF 0.1µF MAX8515A MAX8515 50kΩ 90.1kΩ 1% PGND GND NETWORK ANALYZER SOURCE FB 2.2nF REFERENCE Set R4 to 10kΩ and calculate R3 by: V R3 = OUT - 1 × R4 VFB TEST 2.2nF 10kΩ 1% 1MΩ GAIN = TEST/REFERENCE Figure 2. Test Circuits for Gain and Phase Plots The midband gain is given by: R2 A= R3 Add C4 for high-frequency noise rejection. Determine R2 based on the midband gain required by the isolated power supply. Choose fz based on the power supply small-signal transfer function. Calculate C3 once f z is known. _______________________________________________________________________________________ 5 MAX8515A/MAX8515 Wide-Input 0.6V Shunt Regulators for Isolated DC-to-DC Converters Overvoltage Protection VREG 1.8V INPUT SUPPLY V+ MAX5003 NDRV PGND CON R1 47kΩ C1 0.1µF V R3 = OVP - 1 × R4 VFB OUT IN MAX8515A MAX8515 PGND GND R3 20kΩ 1% C2 0.1µF Figure 4 shows an isolated OVP circuit. R1 limits the current supplied to the photodiode. R2 limits the MAX8515A/MAX8515 input current. R3 and R4 set the trip threshold for the OVP. C1 is the input supply decoupling capacitor. Values for R3 and R4 are chosen based on the needed OVP threshold. For example, a trip threshold of 25% above the rated output voltage is needed for an OVP circuit. The values of R3 can be determined from the following equation once R4 is chosen; 10kΩ is recommended for R4. Then, R3 = 6.2kΩ. R2 C4 where VOVP = 0.8V x 1.25 for the given example. C3 FB Linear Regulator Use an external pass transistor in conjunction with the MAX8515A/MAX8515 to create a linear regulator as shown in Figure 5. Determine the output voltage of the regulator by: R4 10kΩ 1% Figure 3. MAX8515A/MAX8515 Typical Application Circuit, Opto-Feedback Circuit R2 VREG = 0.6V × 1 + R3 Choose R1 to maintain load regulation up to a 2A load. Use the following equation: 6V TO 10V R1 = R1 1.2kΩ FEEDBACK OPTOCOUPLER R2 2kΩ DC-DC OUTPUT 0.8V IN C1 0.1µF 16V MAX8515A MAX8515 PGND GND OUT R3 6.2kΩ 1% FB R4 10kΩ 1% VIN_MIN - VREG - VBE IO_MAX where IO_MAX is the rated maximum output current, which is 2A in this application circuit. VREG is the output voltage of the linear regulator. VBE is the base-to-emitter forward voltage of Q1, and β is the minimum current gain of Q1 at rated load current. VIN is the minimum input voltage at IN. For the typical application circuit, VIN_MIN = 2.375V, VREG = 1.0V, VBE = 0.65V, and β = 180. Choose R1 = 15Ω for fast transient response. C1 is the input decoupling capacitor and C2 is the compensation capacitor. Use a 1µF, 6.3V capacitor for this application. Figure 6 shows a typical load-regulation curve for the circuit in Figure 5. This circuit does not provide short-circuit, overcurrent, or overtemperature protection. Figure 4. MAX8515A/MAX8515 Typical Application Circuit, OVP Circuit (Set to 1V OVP Threshold for 0.8V Nominal Output) 6 ×β _______________________________________________________________________________________ Wide-Input 0.6V Shunt Regulators for Isolated DC-to-DC Converters VREG 1V OUT IN 0.6V REFERENCE R1 MAX8515A MAX8515 VIN IN C1 0.1µF OUT C2 1.0µF MAX8515A MAX8515 GND FB R2 6.65kΩ PGND GND FB Selector Guide R3 10kΩ VIN (V) 2.5 3.3 5 R1 (Ω) 22.1 40.2 82.5 Figure 5. MAX8515A/MAX8515 Typical Application Circuit, Linear Regulator PART INITIAL ACCURACY MAX8515AEXK-T 0.6V, 0.5% feedback TOP MARKS ADX MAX8515AEZK-T 0.6V, 0.5% feedback ADRK MAX8515EXK-T 0.6V, 1% feedback ADY MAX8515EZK-T 0.6V, 1% feedback ADRL Chip Information TRANSISTOR COUNT: 50 PROCESS: BiCMOS LINEAR-REGULATOR LOAD REGULATION 0 -0.5 VCC = 2.5V OUTPUT VOLTAGE (mV) -1.0 -1.5 -2.0 -2.5 -3.0 VCC = 1.2V -3.5 -4.0 CVCC = 220µF -4.5 -5.0 0 0.5 1.0 1.5 2.0 LOAD CURRENT (A) Figure 6. Load Regulation of Linear-Regulator Circuit _______________________________________________________________________________________ 7 MAX8515A/MAX8515 Functional Diagram IO 2A (MAX) Q1 FZT1049A VCC 1.2V TO 2.5V Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) SC70, 5L.EPS MAX8515A/MAX8515 Wide-Input 0.6V Shunt Regulators for Isolated DC-to-DC Converters 8 _______________________________________________________________________________________ Wide-Input 0.6V Shunt Regulators for Isolated DC-to-DC Converters THIN SOT23.EPS _______________________________________________________________________________________ 9 MAX8515A/MAX8515 Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) MAX8515A/MAX8515 Wide-Input 0.6V Shunt Regulators for Isolated DC-to-DC Converters Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.