19-1536; Rev 1; 12/99 MAX1714A Evaluation Kit Features ♦ +5V to +24V Input Voltage Range ♦ Preset 2.5V Output Voltage ♦ 1.0V to 5.5V Adjustable Output ♦ 4A Output Current ♦ 94% Efficient (VOUT = 2.5V, VBATT = 7V, ILOAD = 2A) ♦ 300kHz Switching Frequency ♦ No Current-Sense Resistor ♦ Power-Good Output ♦ Low-Profile Components ♦ Fully Assembled and Tested Ordering Information PART TEMP. RANGE MAX1714AEVKIT 0°C to +70°C IC PACKAGE 20 QSOP Component List DESIGNATION QTY C1 1 DESCRIPTION 10µF, 25V ceramic capacitor (1812) Taiyo Yuden TMK432BJ106KM or Tokin C34Y5U1E106Z C2 1 330µF, 6.3V, 45mΩ C100M low-ESR capacitor Sanyo 6TPB330M or Kemet T510X337M010AS C3 1 0.1µF ceramic capacitor (0805) C4 1 0.22µF ceramic capacitor (1206) C5 1 4.7µF, 10V, X5R ceramic cap (1206) Taiyo Yuden LMK316BJ475ML C6 1 3.3µF, 10V, X5R ceramic cap (1206) Taiyo Yuden LMK316BJ335ML C7 1 2200pF ceramic capacitor (0805) 1 1A, 30V Schottky diode Nihon EP10QY03 or EC10QS03 or Motorola MBRS130LT3 D1 D2 1 100mA, 30V Schottky diode Central Semiconductor CMPSH-3 DESIGNATION QTY DESCRIPTION JU1, JU2 2 2-pin headers L1 1 4.7µH power inductor Sumida CDRH124-4R7MC (shielded), Coiltronics UP2B-4R7 (unshielded) N1A, N1B 1 Dual N-channel MOSFET Fairchild FDS6982A R1, R2, R3, R8, R9 0 Not installed R4 1 100kΩ ±5% resistor (0805) R5, R6 2 1MΩ ±5% resistors (0805) R7 1 20Ω ±5% resistor (0805) R8 1 200Ω ±5% resistor (0805) U1 1 MAX1714AEEP (20-pin QSOP) None 1 Shunt (JU1) None 1 MAX1714A PC board None 1 MAX1714A data sheet None 1 MAX1714A EV kit data sheet ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. Evaluates: MAX1714A General Description The MAX1714A evaluation kit (EV kit) demonstrates a standard 4A application circuit. This DC-DC converter steps down high-voltage batteries and/or AC adapters, generating a precision, low-voltage rail for use as chipset, DRAM, and other low-voltage supplies. For higher current applications up to 12A, refer to the MAX1714A data sheet. The MAX1714A EV kit provides a 2.5V output voltage from a +5V to +24V battery input range. It delivers up to 4A output current with greater than 90% efficiency while operating at a 300kHz switching frequency, and has superior line- and load-transient response. This EV kit is a fully assembled and tested circuit board. It also allows evaluation of other output voltages in the 1.0V to 5.5V range by changing feedback resistors R1 and R2. Evaluates: MAX1714A MAX1714A Evaluation Kit Component Suppliers SUPPLIER PHONE FAX AVX 803-946-0690 803-626-3123 Central Semiconductor 516-435-1110 516-435-1824 Coilcraft 708-639-6400 708-639-1469 Coiltronics 561-241-7876 561-241-9339 Fairchild 408-721-2181 408-721-1635 Kemet 408-986-0424 408-986-1442 Motorola 602-303-5454 602-994-6430 Nihon 847-843-7500 847-843-2798 Sanyo 619-661-6835 619-661-1055 Sumida 708-956-0666 708-956-0702 Taiyo Yuden 408-573-4150 408-573-4159 Tokin 408-432-8020 408-434-0375 Note: Please indicate that you are using the MAX1714A when contacting these component suppliers. Detailed Description Jumper Settings Table 1. Jumper JU1 Functions (Shutdown Mode) On Connected to VCC MAX1714A enabled Off Connected to AGND Shutdown mode, VOUT = 0 Table 2. Jumper JU2 Functions (Low-Noise Mode) SHUNT LOCATION SKIP PIN OPERATIONAL MODE On Connected to VCC Low-noise mode, forced fixedfrequency PWM operation Off Connected to AGND Normal operation, allows automatic PWM/PFM switchover for pulse skipping at light load, resulting in highest efficiency Equipment Needed • +5V to +24V power supply, battery, or notebook AC adapter MAX1714A OUTPUT SHDN PIN SHUNT LOCATION • +5V (at 100mA) DC bias power supply • Dummy load capable of sinking 4A • Digital multimeter (DMM) • 100MHz dual-trace oscilloscope Quick Reference 1) Ensure that the circuit is connected correctly to the supplies and dummy load prior to applying any power. 2) Verify that the shunt is placed across JU1. 3) Turn on battery power prior to +5V bias power; otherwise, the output undervoltage protection timer will time out and the FAULT latch will be set, disabling the regulator until +5V power is cycled or shutdown is toggled (refer to the Output Undervoltage Protection section in the MAX1714A data sheet). 4) Observe the 2.5V output with the DMM and/or oscilloscope. Look at the LX switching-node and MOSFET gate-drive signals while varying the load current. 2 Table 3. Jumper JU3 Functions (Fixed/Adjustable Current-Limit Selection) SHUNT LOCATION ILIM PIN On Connected to VCC Off Connected to REF through voltage-divider R3/R9. Refer to the Current-Limit Circuit section in the MAX1714A data sheet for information on selecting R3/R9. CURRENT-LIMIT THRESHOLD 100mV (default) Adjustable from 50mV to 200mV Evaluating Other Output Voltages The EV kit output is preset to +2.5V. However, the output voltage can also be adjusted between 1.0V and 5.5V by selecting R1 and R2 values. Cut the PC board trace shorting R2, then select feedback resistor R2 in the 5kΩ to 100kΩ range. R1 is then given by: R1 = R2 [(VOUT / VFB) - 1] where VFB = 1.0V. If a 3.3V output is desired, cut the trace shorting R2, then short JU7. _______________________________________________________________________________________ MAX1714A Evaluation Kit JUMPER SHUNT LOCATION TON PIN FREQUENCY (kHz) JU4, JU5, JU6 Off Floating 300 JU4 On JU5, JU6 Off Connected to VCC 200 Connected to REF 450 Connected to AGND 600 JU5 On JU4, JU6 Off JU6 On JU4, JU5 Off IMPORTANT: Don’t change the operating frequency without first recalculating component values because the frequency has a significant effect on the preferred inductor value, peak current-limit level, MOSFET heating, PFM/PWM switchover point, output noise, efficiency, and other critical parameters. Table 5. Troubleshooting Guide SYMPTOM POSSIBLE PROBLEM Circuit won’t start when power is applied. Power-supply sequencing: +5V bias supply was applied first Cycle SHDN by removing and reinstalling JU1. Output overvoltage due to shorted high-side MOSFET Replace the MOSFET. Output overvoltage due to load recovery overshoot Reduce the inductor value, raise the switching frequency, or add more output capacitance. Overload condition Remove the excessive load or raise the ILIM threshold by changing R3/R9. Broken connection, bad MOSFET, or other catastrophic problem Troubleshoot the power stage. Are the DH and DL gatedrive signals present? Is the 2V VREF present? On-time pulses are erratic or have unexpected changes in period. VBATT power source has poor impedance characteristic Add a bulk electrolytic bypass capacitor across the benchtop power supply, or substitute a real battery. Load-transient VOUT waveform shows excess ringing. OR LX switching waveform exhibits double-pulsing (pulses separated only by a 400ns min off-time). Instability due to output capacitors placed at the feedback point Add parasitic PC board trace resistance between the feedback point and the output capacitor. OR Substitute a different capacitor type (OS-CONs, tantalums, or aluminum electrolytics work well). Circuit won’t start when SHDN and +5V bias supply are cycled. SOLUTION _______________________________________________________________________________________ 3 Evaluates: MAX1714A Table 4. Jumper JU4/JU5/JU6 Functions (Switching-Frequency Selection) 4 REF 2V SKIP SHDN GND 5V TO 24V VDD REF VBATT JU4 200kHz JU3 R3 OPEN VCC Figure 1. MAX1714A EV Kit Schematic _______________________________________________________________________________________ R6 1M FLOAT = 300kHz C4 0.22µF JU2 VCC R5 1M 16 7 18 6 3 17 DENOTES HIGH-CURRENT PATH JU5 600kHz JU5 450kHz R9 OPEN JU1 VCC VBIAS +5V 8 AGND TON REF SKIP ILIM SHDN V+ U1 14 VDD VCC 2 9 DL LX DH BST PGOOD FB OUT PGND 15 VCC C6 3.3µF 10V 11 N.C. N.C. N.C. MAX1714A C5 4.7µF 10V R7 20Ω 10 4 5 12 13 20 1 19 R4 100k C3 0.1µF 4 D2 CMPSH-3 2 6 VCC C7 2200pF 1 N1A 3 N1B 7 8 5 PGOOD R8 200Ω D1 R2 SHORT (PC TRACE) L1 4.7µH C1 10µF 25V JU7 R1 OPEN VCC C2 330µF 6.3V VOUT 2.5V 4A Evaluates: MAX1714A MAX1714A Evaluation Kit MAX1714A Evaluation Kit Evaluates: MAX1714A 1.0" Figure 2. MAX1714A EV Kit Component Placement Guide— Component Side 1.0" 1.0" Figure 3. MAX1714A EV Kit PC Board Layout—Component Side Figure 4. MAX1714A EV Kit PC Board Layout—Solder Side _______________________________________________________________________________________ 5 Evaluates: MAX1714A MAX1714A Evaluation Kit NOTES 6 _______________________________________________________________________________________