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| 19-1536; Rev 1; 12/99 MAX1714B Evaluation Kit General Description The MAX1714B 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, dynamic random-access memory (DRAM), and other low-voltage supplies. The MAX1714B EV kit provides a 2.5V output voltage from a +4.5V 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 +4.5V 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 16-Pin QSOP Package o Low-Profile Components o Fully Assembled and Tested Features Evaluates: MAX1714B Ordering Information PART MAX1714BEVKIT TEMP. RANGE 0C to +70C IC PACKAGE 16 QSOP Component List DESIGNATION QTY C1 1 DESCRIPTION 10F, 25V ceramic capacitor (1812) Taiyo Yuden TMK432BJ106KM or Tokin C34Y5U1E106Z 330F, 6.3V 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 Schottky diode Nihon EP10QY03 or EC10QS03, Motorola MBRS130LT3, or International Rectifier 10MQ040N 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), or Coilcraft DO3316P-472 (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) MAX1714BEEE (16-pin QSOP) Shunt (JU1) MAX1714B PC board MAX1714 data sheet MAX1714B EV kit data sheet C2 C3 C4 C5 C6 C7 1 1 1 1 1 1 N1A, N1B R1, R2, R3, R9 R4 R5, R6 R7 R8 U1 None None None None 1 0 1 2 1 1 1 1 1 1 1 D1 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. MAX1714B Evaluation Kit Evaluates: MAX1714B Component Suppliers SUPPLIER Central Semiconductor Coilcraft Coiltronics Fairchild International Rectifier Motorola Nihon Sanyo Sumida Taiyo Yuden Tokin PHONE 516-435-1110 708-639-6400 561-241-7876 408-721-2181 310-322-3331 602-303-5454 847-843-7500 619-661-6835 708-956-0666 408-573-4150 408-432-8020 FAX 516-435-1824 708-639-1469 561-241-9339 408-721-1635 310-322-3332 602-994-6430 847-843-2798 619-661-1055 708-956-0702 408-573-4159 408-434-0375 On Off Connected to VCC Connected to GND 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 2k to 20k 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. Table 1. Jumper JU1 Functions (Shutdown Mode) SHUNT LOCATION SHDN PIN MAX1714B OUTPUT MAX1714B enabled Shutdown mode, VOUT = 0 Note: Please indicate that you are using the MAX1714B when contacting these component suppliers. Recommended Equipment * +5V to +24V power supply, battery, or notebook AC adapter * DC bias power supply, 5V at 100mA * Dummy load capable of sinking 4A * Digital multimeter (DMM) * 100MHz dual-trace oscilloscope Table 2. Jumper JU2 Functions (Low-Noise Mode) SHUNT LOCATION On SKIP PIN Connected to VCC Connected to GND 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. 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 the battery power before the +5V bias power; otherwise, the output undervoltage lockout (UVLO) timer will time out and the FAULT latch will be set, disabling the regulator until +5V power is cycled or shutdown is toggled. 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 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 MAX1714 data sheet for information on selecting R3/R9. CURRENT-LIMIT THRESHOLD 100mV (default) Detailed Description Jumper Settings Tables 1-4 show the functions you can achieve with various jumper settings. 2 Off Adjustable from 50mV to 200mV _______________________________________________________________________________________ MAX1714B Evaluation Kit Evaluates: MAX1714B 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 GND 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 Instability due to low-ESR ceramic or polymer capacitors placed across fast feedback path (FB-GND) 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 LX-FB connection and the ceramic capacitor. OR Substitute a different capacitor type (OS-CONs, tantalums, or aluminum electrolytics work well). _______________________________________________________________________________________ 3 Evaluates: MAX1714B MAX1714B Evaluation Kit Figure 1. MAX1714B EV Kit Schematic VBIAS +5V R7 20 C5 4.7F 10V VCC D2 CMPSH-3 5 6 N1B 3 C3 0.1F 7 2 SKIP OUT 1 3 R8 200 PGOOD GND 8 JU7 FLOAT = 300kHz JU6 600kHz R4 100k VCC 7 C7 2200pF VCC R1 OPEN 4 N1A D1 8 L1 4.7H 15 BST DH LX 5 VCC R3 OPEN 14 JU2 6 R6 1M 12 TON C4 0.22F REF FB ILIM DL 9 16 1 4 C1 10F 25V C6 3.3F 10V VCC JU1 13 V+ 10 VDD 11 VCC VCC R5 1M SHDN 2 4 U1 MAX1714B JU3 VOUT 2.5V 4A C2 330F 6.3V JU5 450kHz PGOOD R2 SHORT (PC TRACE) VBATT 4.5V TO 24V SHDN REF R9 OPEN SKIP REF 2V VCC _______________________________________________________________________________________ JU4 200kHz MAX1714B Evaluation Kit Evaluates: MAX1714B 1.0" Figure 2. MAX1714B EV Kit Component Placement Guide-- Component Side 1.0" 1.0" Figure 3. MAX1714B EV Kit PC Board Layout--Component Side Figure 4. MAX1714B EV Kit PC Board Layout--Solder Side _______________________________________________________________________________________ 5 MAX1714B Evaluation Kit Evaluates: MAX1714B NOTES 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 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. |
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