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| 19-1536; Rev 1; 12/99 MAX1714A Evaluation Kit 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. o +5V to +24V Input Voltage Range o Preset 2.5V Output Voltage o 1.0V to 5.5V Adjustable Output o 4A Output Current o 94% Efficient (VOUT = 2.5V, VBATT = 7V, ILOAD = 2A) o 300kHz Switching Frequency o No Current-Sense Resistor o Power-Good Output o Low-Profile Components o Fully Assembled and Tested Features Evaluates: MAX1714A Ordering Information PART MAX1714AEVKIT TEMP. RANGE 0C to +70C IC PACKAGE 20 QSOP Component List DESIGNATION QTY C1 1 DESCRIPTION 10F, 25V ceramic capacitor (1812) Taiyo Yuden TMK432BJ106KM or Tokin C34Y5U1E106Z 330F, 6.3V, 45m C100M low-ESR capacitor Sanyo 6TPB330M or Kemet T510X337M010AS 0.1F ceramic capacitor (0805) 0.22F ceramic capacitor (1206) 4.7F, 10V, X5R ceramic cap (1206) Taiyo Yuden LMK316BJ475ML 3.3F, 10V, X5R ceramic cap (1206) Taiyo Yuden LMK316BJ335ML 2200pF ceramic capacitor (0805) 1A, 30V Schottky diode Nihon EP10QY03 or EC10QS03 or Motorola MBRS130LT3 100mA, 30V Schottky diode Central Semiconductor CMPSH-3 DESIGNATION QTY JU1, JU2 L1 2 1 DESCRIPTION 2-pin headers 4.7H power inductor Sumida CDRH124-4R7MC (shielded), Coiltronics UP2B-4R7 (unshielded) Dual N-channel MOSFET Fairchild FDS6982A Not installed 100k 5% resistor (0805) 1M 5% resistors (0805) 20 5% resistor (0805) 200 5% resistor (0805) MAX1714AEEP (20-pin QSOP) Shunt (JU1) MAX1714A PC board MAX1714A data sheet MAX1714A EV kit data sheet C2 C3 C4 C5 C6 C7 D1 1 1 1 1 1 1 1 N1A, N1B R1, R2, R3, R8, R9 R4 R5, R6 R7 R8 U1 None None None None 1 0 1 2 1 1 1 1 1 1 1 D2 1 ________________________________________________________________ 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. MAX1714A Evaluation Kit Evaluates: MAX1714A Component Suppliers SUPPLIER AVX Central Semiconductor Coilcraft Coiltronics Fairchild Kemet Motorola Nihon Sanyo Sumida Taiyo Yuden Tokin PHONE 803-946-0690 516-435-1110 708-639-6400 561-241-7876 408-721-2181 408-986-0424 602-303-5454 847-843-7500 619-661-6835 708-956-0666 408-573-4150 408-432-8020 FAX 803-626-3123 516-435-1824 708-639-1469 561-241-9339 408-721-1635 408-986-1442 602-994-6430 847-843-2798 619-661-1055 708-956-0702 408-573-4159 408-434-0375 Off On Connected to VCC Connected to AGND Detailed Description Jumper Settings Table 1. Jumper JU1 Functions (Shutdown Mode) SHUNT LOCATION SHDN PIN MAX1714A OUTPUT MAX1714A enabled Shutdown mode, VOUT = 0 Table 2. Jumper JU2 Functions (Low-Noise Mode) SHUNT LOCATION On SKIP PIN Connected to VCC Connected to AGND OPERATIONAL MODE Low-noise mode, forced fixedfrequency PWM operation Normal operation, allows automatic PWM/PFM switchover for pulse skipping at light load, resulting in highest efficiency Note: Please indicate that you are using the MAX1714A when contacting these component suppliers. Equipment Needed * +5V to +24V power supply, battery, or notebook AC adapter * +5V (at 100mA) DC bias power supply * Dummy load capable of sinking 4A * Digital multimeter (DMM) * 100MHz dual-trace oscilloscope Off Table 3. Jumper JU3 Functions (Fixed/Adjustable Current-Limit Selection) SHUNT LOCATION On ILIM PIN Connected to VCC 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) 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. Off 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 5k to 100k 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. 2 _______________________________________________________________________________________ MAX1714A Evaluation Kit Evaluates: MAX1714A Table 4. Jumper JU4/JU5/JU6 Functions (Switching-Frequency Selection) JUMPER JU4, JU5, JU6 JU4 JU5, JU6 JU5 JU4, JU6 JU6 JU4, JU5 SHUNT LOCATION Off On Off On Off On Off TON PIN Floating Connected to VCC Connected to REF Connected to AGND FREQUENCY (kHz) 300 200 450 600 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 Circuit won't start when power is applied. POSSIBLE PROBLEM Power-supply sequencing: +5V bias supply was applied first Output overvoltage due to shorted high-side MOSFET Output overvoltage due to load recovery overshoot Circuit won't start when SHDN and +5V bias supply are cycled. Overload condition Broken connection, bad MOSFET, or other catastrophic problem On-time pulses are erratic or have unexpected changes in period. Load-transient VOUT waveform shows excess ringing. OR LX switching waveform exhibits double-pulsing (pulses separated only by a 400ns min off-time). VBATT power source has poor impedance characteristic SOLUTION Cycle SHDN by removing and reinstalling JU1. Replace the MOSFET. Reduce the inductor value, raise the switching frequency, or add more output capacitance. Remove the excessive load or raise the ILIM threshold by changing R3/R9. Troubleshoot the power stage. Are the DH and DL gatedrive signals present? Is the 2V VREF present? Add a bulk electrolytic bypass capacitor across the benchtop power supply, or substitute a real battery. 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). Instability due to output capacitors placed at the feedback point _______________________________________________________________________________________ 3 Evaluates: MAX1714A MAX1714A Evaluation Kit Figure 1. MAX1714A EV Kit Schematic R7 20 C5 4.7F 10V VCC D2 CMPSH-3 5 6 N1B 3 C3 0.1F 78 2 N1A 1 5 4 10 C7 2200pF VCC JU7 D1 L1 4.7H 19 BST DH LX 6 VCC R3 OPEN 18 SKIP OUT 7 R6 1M 16 TON PGOOD N.C. N.C. N.C. 2 9 11 AGND 8 C4 0.22F REF FB PGND 12 JU2 ILIM DL 13 20 1 4 C1 10F 25V C6 3.3F 10V JU1 17 V+ 14 VDD 15 VCC VCC R5 1M SHDN 3 4 U1 MAX1714A JU3 VOUT 2.5V 4A C2 330F 6.3V R8 200 R1 OPEN JU5 450kHz JU5 600kHz FLOAT = 300kHz R4 100k VCC PGOOD R2 SHORT (PC TRACE) DENOTES HIGH-CURRENT PATH VBIAS +5V VBATT 5V TO 24V GND VCC SHDN REF R9 OPEN SKIP REF 2V VDD _______________________________________________________________________________________ JU4 200kHz 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 MAX1714A Evaluation Kit Evaluates: MAX1714A NOTES 6 _______________________________________________________________________________________ |
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