19-2156; Rev 0; 9/01 MAX1809 Evaluation Kit Features ♦ ±3A Output Current ♦ Up to 1MHz Switching Frequency ♦ Up to 93% Efficiency ♦ Synchronous Rectification for Improved Efficiency ♦ Output Voltage: +1.1V to VIN Adjustable ♦ +3V to +5.5V Input Voltage Range ♦ Less than 1µA Typical IC Shutdown Current ♦ Surface-Mount Construction ♦ Fully Assembled and Tested Ordering Information PART TEMP. RANGE MAX1809EVKIT 0°C to +70°C IC PACKAGE 16 QSOP Component List DESIGNATION QTY DESCRIPTION C1 1 33µF, 6.3V, X5R ceramic capacitor TDK C3225XR0J336V C2, C9 0 Not installed C3 1 270µF, 2V, 15mΩ ESR SP capacitor Panasonic EEFUE0D271R C4 1 0.01µF, 50V, X7R ceramic C5 C6 C7, C8 D1, D2 D3 1 2.2µF, 10V, X5R ceramic capacitor Taiyo Yuden LMK212BJ225MG TDK C2012X5R1A225M 1 1µF, 10V, X7R ceramic capacitor Taiyo Yuden LMK212BJ105MG Murata GRM40X7R105K010 TDK C2012X5R1C105K 2 1000pF, 50V, C0G ceramic capacitors 0 Not installed 1 Diode Diodes Inc. 1N4148W Fairchild MMSD4148 General Semiconductor 1N4148W DESIGNATION QTY JU1, JU2 2 2-pin headers JU3 0 Not installed 1 1µH, 3A inductor Sumida 4762-T072 (CDRH6D28 type) Toko A920CY-1R0M (D62CB type) L1 DESCRIPTION R1, R2 2 10kΩ ±1% resistors R3 1 10Ω ±5%resistor R4 1 1MΩ ±5% resistor R5 1 130kΩ ±1% resistor R6 1 R7 1 0.012Ω ±1%, 0.5W sense resistor Vishay Dale WSL-2010-R012F IRC LRC-LR2010-01-R012-F 100Ω ±5% resistor R8 0 Not installed U1 1 MAX1809EEE (16-QSOP) None 2 Shunts for JU1 and JU2 ________________________________________________________________ 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: MAX1809 General Description The MAX1809 evaluation kit (EV kit) provides a +1.1V output voltage from a +3V to +5.5V input source. It sources and sinks up to 3A of current. The MAX1809 is a step-down switching regulator with an internal synchronous-rectifier that operates up to 1MHz, minimizing external components. The device features a resistorprogrammable, fixed off-time current-mode operation for superior load- and line-transient response, and achieves efficiencies up to 93%. Evaluates: MAX1809 MAX1809 Evaluation Kit Component Suppliers SUPPLIER PHONE FAX Diodes Inc. 805-446-4800 805-381-3899 Fairchild 888-522-5372 — General Semiconductor 760-804-9258 760-804-9259 IRC 361-992-7900 361-992-3377 Murata 770-436-1300 770-436-3030 Nihon 661-867-2555 661-867-2698 Panasonic 201-392-7522 201-392-4441 Sumida 847-545-6700 847-545-6720 Taiyo Yuden 800-348-2496 847-925-0899 TDK 847-803-6100 847-390-4405 Toko 847-297-0070 847-699-1194 Vishay Dale 402-564-3131 402-563-6296 Note: Please indicate that you are using the MAX1809 when contacting these suppliers Quick Start Table 1. Jumper JU1 Functions SHUNT LOCATION SHDN PIN MAX1809 OUTPUT Open Connected to GND through 1MΩ (R4) Shutdown mode, VOUT = 0 Closed (Default) Connected to VIN MAX1809 enabled, VOUT = +1.1V. Output Voltage Selection The MAX1809 EV kit is shipped with the output voltage set to +1.1V. To change the output voltage, follow the configurations stated in Table 2. Table 2. Setting the MAX1809 Output Voltage JU2 Closed (Default) Open R7 = 100Ω, R8 = open; external voltage applied to the pads labeled EXTREF and AGND VOUT = VEXTREF Open R7 = 100Ω, R8 = open; external voltage applied to the pads labeled VDD and AGND VOUT = VDD/2 1) Verify that a shunt is on JU1 (shutdown disabled) to enable operation and on JU2 to set the output voltage to +1.1V. Detailed Description Jumper Selection Jumper JU1 selects the shutdown mode of the MAX1809. Table 1 lists the jumper options. Jumper JU2 connects EXTREF to REF, setting the output voltage of the MAX1809 to +1.1V. Refer to the Output Voltage Selection section. 2 VOUT = +1.1V VOUT = +1.1V x (1 + R7/R8) Closed The MAX1809 EV kit provides a +1.1V output voltage from a +3V to +5.5V input voltage. It sources or sinks up to 3A of output current. Continuous operation at 3A with high ambient temperatures may be limited due to thermal considerations (see the MAX1809 data sheet). R7 = 100Ω, R8 = open OUTPUT VOLTAGE R7 = 10kΩ, R8 = installed The MAX1809 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. 2) Connect a voltmeter and load (if any) to VOUT and GND. 3) Connect a +3V to +5.5V supply to the pads marked VIN and GND. 4) Turn on the power and verify that the output voltage is +1.1V. 5) Refer to the Output Voltage Selection section to modify the board for a different output voltage. CONDITION When the shunt at JU2 is removed, observe the voltage limits on EXTREF as recommended in the MAX1809 data sheet. Failure to observe these limits can cause the part to enter abnormal operating conditions and might cause the part to be damaged. For output voltages above +1.6V, replace capacitor C3 with a higher voltage rated capacitor. R7 is set at 100Ω for configurations that do not use R8 to adjust the output voltage. This 100Ω allows the MAX1809 to power up into a sinking current mode. Refer to the MAX1809 data sheet for a detailed description of this function. _______________________________________________________________________________________ MAX1809 Evaluation Kit Test Setup In applications that require active termination, the MAX1809 is required to both source and sink current. Figures 1 and 2 below show how to set up the MAX1809 EV kit for sourcing and sinking current. For sourcing-mode test setup (Figure 1), connect an external load to the pads labeled VOUT and GND. VDC LOAD (SOURCING) ISOURCE In the sinking-mode test setup (Figure 2), beware of back-biasing the EV kit with too high a voltage during the turn-on sequence. The supply to the EV kit (VDC1) must be powered on before the supply is connected to the load (VDC2). Failure to do so will result in permanent damage to the evaluation kit. Also, do not source current to the load supply (VDC2) as it can damage that supply. Follow these procedures when conducting a sinkingmode test: 1) Disconnect the load from the output of the MAX1809 EV kit. 2) Connect a preload across VIN and GND. Use the following equation to determine the minimum required preload current. V Ipreload > 3A OUT VIN 3) Power up the MAX1809 EV kit. 4) Set the load at the highest impedance. 5) Set the load supply (VDC2) to the same voltage as the output of the MAX1809 EV kit. 6) Connect the load to the output of the MAX1809 EV kit (VOUT and GND). 7) Adjust the load and increase VDC2 until the desired sinking current is reached. Before powering down the MAX1809, disconnect the load from the output of the MAX1809 EV kit to prevent driving a high voltage into the output of the MAX1809 while it is off. Figure 1. Test Setup (Sourcing) Load Transient Experiment VDC1 VDC2 PRE-LOAD LOAD (SINKING) IPRE-LOAD Figure 2. Test Setup (Sinking) ISINK One interesting experiment is to subject the output to fast load transients. Most benchtop electronic loads intended for power-supply testing lack the ability to subject the DC-DC converter to ultra-fast load transients. Emulating the termination supply’s fast di/dt requires at least 10A/µs load transients. An easy method for generating such an abusive load transient is to solder a MOSFET, such as an MTP3055 or 12N05, directly across VOUT and GND. Then drive its gate with a strong pulse generator at a low duty cycle (=10%) to minimize heat stress in the MOSFET. Adjust the highlevel output voltage of the pulse generator to vary the load current. Alternatively, control the load current with a load resistor in series with the MOSFET’s drain, and drive the MOSFET fully on. Remember to include the expected on-resistance of the MOSFET in the load resistor calculation. _______________________________________________________________________________________ 3 Evaluates: MAX1809 Note: The switching frequency of the MAX1809 EV kit is 600kHz when the input voltage is +5V and the output voltage is +1.1V. This frequency will change when the input or output voltages change. When operated from a +3.3V input voltage, the switching frequency will be 450kHz. Do not operate the MAX1809 above 1MHz. To set the switching frequency, change the tOFF resistor (R5) and the inductor. Refer to the MAX1809 data sheet to determine the values. Evaluates: MAX1809 MAX1809 Evaluation Kit To perform a fast transient test that goes from sourcing mode to sinking mode and back, first arrange the setup as in the sinking mode. Add the dummy MOSFET from VOUT to GND as described in the previous paragraph. Power up the MAX1809 and set the sinking current to the desired level, then use the pulse generator to pull the appropriate sourcing current through the dummy MOSFET. In this situation, the dummy MOSFET will be sinking both the external sinking current and the sourcing current from the output of the MAX1809. As an example, if the transient is required to go from -1A (sinking) to +2A (sourcing), then the dummy MOSFET needs to sink +3A when it is turned on. Figure 3 illustrates this setup. VDC2 1A L SINK LOAD VOUT Note: Do not place a current meter in the load path to determine the load current because the additional resistance and inductance will interfere with fast load transients. It is best to observe the inductor current with a calibrated AC-current probe, such as a Tektronix AM503. In the buck topology, the load current is equal to the average value of the inductor current. The MAX1809 EV kit is optimized to handle load transients from -2A to +2A. For load steps that are larger than 4A total, refer to the MAX1809 data sheet to calculate the required inductance and output capacitance. Optimizing for +3.3V Input Supplies The components selected for the MAX1809 EV kit are optimized for an input voltage of +5V. When operating from a +3.3V input supply, change L1 to 0.68µH (Murata LQS66CR68M04M00) and R5 to 73.2kΩ ±1%. This increases the switching frequency to 810MHz when sourcing current and to 970MHz when sinking current. LX Improving Efficiency SOURCE LOAD COUT MAX1809 0A–3A GND The MAX1809 EV kit has footprints for Schottky diodes across the internal PMOS and NMOS. For lowest cost implementation, these Schottky diodes can be omitted. For maximum efficiency, place a 0.5A low-leakage Schottky, such as Nihon EP5Q03L, in positions D1 and D2. Figure 3. Load Transient Setup 4 _______________________________________________________________________________________ MAX1809 Evaluation Kit Evaluates: MAX1809 +3V TO +5.5V VIN GND C1 33µF R3 10Ω 2 IN 12 C5 2.2µF 16 LX LX 14 3 LX VCC JU1 1 R4 1MΩ C4 0.01µF EXTREF U1 D3 REF TOFF JU3 OPEN R8 OPEN C6 1.0µF GND 11 R1 10kΩ GND 10 VDD C7 1000pF R7 100Ω C3 270µF 2V 8 SS 7 VOUT C2 OPEN C9 OPEN FB EXTREF D2 OPEN 15 PGND 13 PGND MAX1809 6 R5 130kΩ 1% SS R6 0.012Ω 1% L1 1µH SHDN SS 5 D1 OPEN 4 IN GND 9 JU2 GND C8 1000pF R2 10kΩ Figure 4. MAX1809 EV Kit Schematic _______________________________________________________________________________________ 5 Evaluates: MAX1809 MAX1809 Evaluation Kit 1.0" 1.0" Figure 5. MAX1809 EV Kit Component Placement Guide— Component Side 1.0" Figure 6. MAX1809 EV Kit PC Board Layout—Component Side 1.0" Figure 7. MAX1809 EV Kit PC Board Layout—Solder Side Figure 8. MAX1809 EV Kit Component Placement Guide— 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 © 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.