19-2469; Rev 0; 5/02 MAX1972 Evaluation Kit Features ♦ Current-Mode, 1.4MHz Fixed-Frequency PWM Operation ♦ Dual-Output 180° Out-of-Phase Operation Reduces Input Ripple Current ♦ ±1% Output Accuracy Over Load, Line, and Temperature Ranges ♦ 750mA Guaranteed Output Current ♦ 2.6V to 5.5V Input ♦ Power-On Reset Output (POR) ♦ Power-Fail Output (MAX1970 and MAX1972) ♦ Power-On Reset Input (MAX1971) Selector Guide ♦ Ultra-Compact Design with Small External Components ♦ Outputs Adjustable from 0.8V to VIN PART POR DELAY TIME (TYP) RSI PFO FREQUENCY MAX1970EEE 16.6ms No Yes 1.4MHz MAX1971EEE 175ms Yes No 0.7MHz ♦ All Ceramic Capacitor Application MAX1972EEE 175ms No Yes 1.4MHz ♦ Soft-Start Reduces Inrush Current ♦ 1.8V/3.3V and 1.5V/2.5V Preset ♦ Fully Assembled and Tested Ordering Information Component Suppliers SUPPLIER Murata PHONE 770-436-1300 WEBSITE www.murata.com Sumida 847-956-0666 www.sumida.com Taiyo-Yuden 408-573-4150 www.taiyo-yuden.com PART MAX1972EVKIT TEMP RANGE IC PACKAGE -40°C to +85°C 16 QSOP Note: To evaluate the MAX1970 or MAX1971, request free samples of these parts with the MAX1972EVKIT. Component List DESIGNATION QTY C1 C2, C3 C4, C7 1 2 2 DESCRIPTION 10µF ±20%, 6.3V X5R ceramic capacitor (1206) Taiyo-Yuden JMK316BJ106ML DESIGNATION QTY DESCRIPTION L1, L2 2 4.7µH ±30%, 0.9A, 80mΩ inductors Sumida CDRH3D16-4R7 R1 1 10Ω ±5% resistor (0603) 0.1µF ±10%, 16V X7R ceramic capacitors (0603) Taiyo-Yuden EMK107BJ104KA R2, R3 2 100kΩ ±5% resistors (0603) R4 1 82kΩ ±5% resistor (0603) R5, R8 2 0Ω resistors (0603) 620pF ±10%, 50V X7R ceramic capacitors (0603) Murata GRM39X7R621K050AD R6, R9, R10 0 Not installed R7 1 39kΩ ±5% resistor (0603) U1 1 MAX1972EEE (16-pin QSOP) None 3 Shunts None 1 MAX1972EVKIT PC board None 1 MAX1970/MAX1971/MAX1972 data sheet C5, C6 2 10µF ±20%, 4V X5R ceramic capacitors (0805) Taiyo-Yuden AMK212BJ106MG JU1, JU2, JU3 3 3-pin headers ________________________________________________________________ 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 Evaluates: MAX1970/MAX1971/MAX1972 General Description The MAX1972 evaluation kit (EV kit) is a fully assembled and tested circuit board that evaluates the MAX1970 family of dual step-down regulators. The circuit operates from an input voltage of 2.6V to 5.5V, and delivers a minimum of 750mA on each output. The output voltages are programmable from 0.8V to VIN using external feedback resistors, or they can be preset to 3.3V or 1.8V for output 1, and 2.5V or 1.5V for output 2. The board has a MAX1972 installed, but it can also be used to evaluate the MAX1970 and the MAX1971. The MAX1971 features a reset input (RSI), while the MAX1970/MAX1972 feature a power-fail output (PFO). Evaluates: MAX1970/MAX1971/MAX1972 MAX1972 Evaluation Kit Quick Start The MAX1972 EV kit is a fully assembled and tested surface-mount board. Follow the steps below to verify board operation. Do not turn on the power supply until all connections are completed: 1) Connect a voltmeter and load from OUT1 to GND, and another voltmeter and load from OUT2 to GND. 2) Verify the JU1 shunt is across pins 1 and 2. 3) Connect the input supply (preset to 2.6V to 5.5V) to the pads marked IN and GND. 4) Configure JU2 and JU3 for desired output voltages (see Table 1 and Table 2). 5) Turn on the power supply and verify the output voltages. Detailed Description Table 2. JU3 Functions SHUNT LOCATION FBSEL2 PIN OUT2 1, 2 VCC 2.5V 2, 3 GND 1.5V None Not Connected Adjustable 1.2V to VIN Table 3. JU1 Functions SHUNT LOCATION FBSEL3 PIN OUT3 1, 2 VCC Enabled 2, 3 GND Shutdown Jumper Selection EN Function JU1 is used to enable shutdown mode (see Table 3). For normal device operation, connect the JU1 shunt between pins 1 and 2. To place the part in shutdown mode, connect the JU1 shunt between pins 2 and 3. This turns off both outputs and reduces the input supply current to approximately 1µA. Preset Output Voltages Each output can be set to one of two preset voltages. This is done by using JU2 and JU3. See Table 1 and Table 2 for the output voltages and corresponding jumper settings. The installed compensation resistors (R4 and R7) are selected for VOUT1 = 3.3V and VOUT2 = 1.5V. For best performance, these need to be changed for different output voltages. Refer to the MAX1970/MAX1971/ MAX1972 data sheet for details on selecting compensation components. Table 1. JU2 Functions SHUNT LOCATION FBSEL1 PIN OUT1 1, 2 VCC 3.3V 2, 3 GND 1.8V None Not Connected Adjustable 0.8V to VIN Adjusting the Output Voltage In addition to two preset output voltages, OUT1 can be set to any voltage between 0.8V and VIN, and OUT2 can bet set to any voltage between 1.2V and VIN. For output voltages greater than 3.3V, change the output capacitors (C5 and C6) to higher-voltage-rated capacitors such as Taiyo-Yuden JMK316BJ106ML (10µF, 6.3V). Use the following procedure to set the voltage of OUT1 from 1.2V to VIN: 1) Remove the shunt from JU2. 2) Remove R5. 3) Select a resistor value for R6 from 10kΩ to 30kΩ. 4) Calculate a resistor value for R5 from: V R5 = R6 × OUT1 - 1 1.2 5) Install the selected resistors R5 and R6. Use the following procedure to set the voltage of OUT2 from 1.2V to VIN: 1) Remove the shunt from JU3. 2) Remove R8. 3) Select a resistor value for R9 from 10kΩ to 30kΩ. 4) Calculate a resistor value for R8 from: V R8 = R9 × OUT2 - 1 1.2 5) Install the selected resistors R8 and R9. 2 _______________________________________________________________________________________ MAX1972 Evaluation Kit 3) Remove R5. 4) Make sure that VOUT2 is set to a value greater than 1.2V (either using a voltage preset or a resistordivider). 5) Select R5 and R10 so the current is about 100µA flowing through R5 and R10: I R5 =I R10 = (VOUT2 - 1.2V) R10 (approximately equal to 100µA) 6) Calculate a resistor value for R5 from: R5 = R10 × (1.2V - VOUT1) (VOUT2 - 1.2V) 7) Install the selected resistors R5 and R10. The installed compensation resistors (R4 and R7) are selected for VOUT1 = 3.3V and VOUT2 = 1.5V. For best performance, these need to be changed for different output voltages. Refer to the MAX1970/MAX1971/ MAX1972 data sheet for details on selecting compensation components. Evaluating the MAX1970 or MAX1971 Although the MAX1972 evaluation kit is assembled with the MAX1972, it can also be used to evaluate the MAX1970 and the MAX1971. Free samples of these parts can be obtained from Maxim. To evaluate the MAX1970/MAX1971, first carefully remove the MAX1972, and replace it with the MAX1970 or MAX1971. For the MAX1971 only, remove R3. Use Figure 2 to locate these pads. Since the MAX1971 operates at 700kHz, external components may need to be optimized. Refer to the MAX1970/MAX1971/MAX1972 data sheet for details on selecting these components. Evaluating Reset Input (MAX1971) Reset input (RSI) is an input available only on the MAX1971. To evaluate the MAX1971, first follow the procedure given in the Evaluating the MAX1970 or MAX1971 section. This input is normally held low. A positive pulse on the RSI/PFO pad causes the POR function to reset. Note: The RSI/PFO pad is used for RSI when the MAX1971 is installed. With the MAX1970 or MAX1972 installed, the RSI/PFO pad is used for PFO. Evaluating Power-On Reset (POR) POR is an output that provides a delayed signal after the outputs reach 92% of their regulated voltages after startup. Refer to the MAX1970/MAX1971/MAX1972 data sheet for details of this feature. A POR pad is provided on the evaluation kit so that this feature can be tested. Evaluating Power-Fail Output (MAX1970/MAX1972) Power-fail output (PFO) is a feature of the MAX1970 and MAX1972. PFO is an output that is typically used to indicate that the IC’s input voltage has dropped below 3.94V. Refer to the MAX1970/MAX1971/ MAX1972 data sheet for details of this feature. Note: The RSI/PFO pad is used for RSI when the MAX1971 is installed. With the MAX1970 or MAX1972 installed, the RSI/PFO pad is used for PFO. _______________________________________________________________________________________ 3 Evaluates: MAX1970/MAX1971/MAX1972 If VOUT2 > 1.2V, then VOUT1 can be set to a voltage as low as 0.8V. Use the following procedure to set VOUT1: 1) Remove the shunt from JU2. 2) Remove R6 (if installed). Evaluates: MAX1970/MAX1971/MAX1972 MAX1972 Evaluation Kit IN 2.6V TO 5.5V VCC C1 10µF C2 0.1µF R3 100kΩ 14 RSI/PFO GND VCC R1 10Ω 11 C4 620pF R4 82kΩ R7 39kΩ C7 620pF 3 6 VCC IN PFO POR LX1 COMP1 L1 4.7µH OUT1 FB1 C5 10µF 1 2 3 4 MAX1972 R6 OPEN EN JU2 13 LX2 15 R10 OPEN L2 4.7µH OUT2 FBSEL1 R8 0Ω JU3 12 7 C3 0.1µF FB2 FBSEL2 C6 10µF 5 REF GND PGND 8 16 R9 OPEN Figure 1. MAX1972 EV Kit Schematic 4 GND VCC VCC 1 2 3 10 1 COMP2 U1 JU1 POR 9 R5 0Ω VCC 1 2 3 R2 100kΩ 2 _______________________________________________________________________________________ MAX1972 Evaluation Kit Figure 3. MAX1972 EV Kit PC Board Layout—Component Side _______________________________________________________________________________________ 5 Evaluates: MAX1970/MAX1971/MAX1972 Figure 2. MAX1972 EV Kit Component Placement Guide— Component Side Evaluates: MAX1970/MAX1971/MAX1972 MAX1972 Evaluation Kit Figure 4. MAX1972 EV Kit PC Board Layout—Solder Side 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. 6 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.