19-2080; Rev 0; 07/01 MAX1844 Evaluation Kit Features ♦ 7V to 24V Input Voltage Range ♦ Accurate Current Sense ♦ Preset 1.8V/2.5V Output Voltage ♦ 1.0V to 5.5V Adjustable Output ♦ 4A Output Current ♦ 300kHz Switching Frequency ♦ Power-Good Output ♦ Over/Undervoltage Protection ♦ 20-Pin QSOP Package ♦ Low-Profile Components ♦ Fully Assembled and Tested Ordering Information PART TEMP. RANGE 0oC to +70oC MAX1844EVKIT IC PACKAGE 20 QSOP Component List DESIGNATION QTY C1 1 DESCRIPTION 10µF, 25V ceramic capacitor (1812) Taiyo Yuden TMK432BJ106KM or TDK C4532X5R1E106M DESIGNATION QTY DESCRIPTION L1 1 4.7µH power inductor Sumida CDRH124-4R7MC N1A, N1B 1 Dual N-channel MOSFET Fairchild FDS6982A R1, R2, R11, R13, R14, R15 0 Not installed (0805) C2 1 330µF, 6.3V 40mΩ low-ESR capacitor Sanyo 6TPB330M C3 1 0.1µF ceramic capacitor (0805) R3 1 130kΩ ±1% resistor (0805) R4 1 100kΩ ±5% resistor (0805) C4 1 0.22µF ceramic capacitor (1206) 2 1MΩ ±5% resistors (0805) 1 4.7µF, 10V X5R ceramic capacitor (1206) Taiyo Yuden LMK316BJ475ML R5, R6 C5 R7 1 20Ω ±5% resistor (0805) R8 1 200Ω ±5% resistor (0805) 3.3µF, 10V X5R ceramic capacitor (1206) Taiyo Yuden LMK316BJ335ML R9 1 274kΩ ±1% resistor (0805) R10 1 0.015Ω ±1% 1/2W resistor (2010) IRC LR2010-01-R015-F or Dale WSL-2010-R015F C6 C7 D1 D2 1 1 2200pF ceramic capacitor (0805) 1 1A Schottky diode Nihon EP10QY03, International Rectifier 10MQ040N, or Nihon EC10QS03 1 100mA, 30V Schottky diode Central Semiconductor CMPSH-3 U1 1 MAX1844EEP (20-pin QSOP) JU1, JU2 2 2-pin headers JU9, JU10 2 3-pin headers None 4 Shunts (JU1, JU2, JU9, JU10) None 1 MAX1844 PC board None 1 MAX1844 data sheet None 1 MAX1844 EV kit data sheet ________________________________________________________________ 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: MAX1844 General Description The MAX1844 evaluation kit (EV kit) demonstrates the MAX1844’s 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. The MAX1844 EV kit provides a 1.8V output voltage from a 7V to 24V battery input range. It delivers up to 4A output current with greater than 90% efficiency. The EV kit operates at 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 the evaluation of other output voltages in the 1.0V to 5.5V range by changing feedback resistors R1 and R2. Evaluates: MAX1844 MAX1844 Evaluation Kit SUPPLIER PHONE FAX Central Semiconductor 516-435-1110 516-435-1824 Dale 402-564-3131 402-563-6296 Fairchild 408-721-2181 408-721-1635 IR 310-322-3331 310-252-7175 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 JU7, then select feedback resistor R2 in the 5kΩ to 50kΩ range. R1 is then given by: R1 = R2 ((VOUT / VFB) - 1) where VFB = 1.0V. See MAX1844 data sheet for optimizing components for output voltage selection. IRC 361-992-7900 361-992-3377 Jumper Settings Nihon 847-843-7500 847-843-2798 Sanyo 619-661-6835 619-661-1055 Component Suppliers Sumida 708-956-0666 708-956-0702 Taiyo Yuden 408-573-4150 408-573-4159 TDK 847-390-4373 847-390-4428 Note: Please indicate that you are using the MAX1844 when contacting these component suppliers. Table 1. Jumper JU1 Functions (Shutdown Mode) SHUNT LOCATION SHDN/PIN MAX1844 OUTPUT ON Connected to VCC MAX1844 enabled OFF Connected to GND Shutdown mode, VOUT = 0 Equipment Needed • 7V to 24V power supply, battery, or notebook AC adapter • DC bias power supply, 5V at 100mA • Dummy load capable of sinking 4A Table 2. Jumper JU2 Functions (Low-Noise Mode) SHUNT LOCATION SKIP/PIN ON Connected to VCC Low-noise mode, forced fixed-frequency PWM operation. Connected to GND Normal operation, allows automatic PWM/PFM switchover for pulse skipping at light load, resulting in highest efficiency. • Digital multimeter (DMM) • 100MHz dual-trace oscilloscope Quick Start 1) Ensure that the circuit is connected correctly to the supplies and dummy load prior to applying any power. OFF 2) Verify that the shunts are across JU1, JU2, JU9 pins 1 and 2, and JU10 pins 2 and 3. 3) Turn on battery power prior to +5V bias power; otherwise, the output 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 1.8V output with the DMM and/or oscilloscope. Look at the LX switching-node and MOSFET gate-drive signals while varying the load current. Table 3. Jumper JU3 Functions (Fixed/Adjustable Current-Limit Selection) SHUNT LOCATION ILIM PIN CURRENT-LIMIT THRESHOLD ON Connected to VCC, (remove R3/R9 divider) 100mV OFF Connected to REF through voltage-divider R3/R9. Refer to the Current-Limit Circuit section in the MAX1844 data sheet for information on selecting R3/R9. Detailed Description Evaluating Other Output Voltages The EV kit output is preset to +1.8V. If a 2.5V output is desired, cut the trace shorting JU7 and install a short across R2. 2 OPERATIONAL MODE _______________________________________________________________________________________ Adjustable from 25mV to 200mV. Programmed for 65mV by R3 and R9. MAX1844 Evaluation Kit JU4 JU5 JU6 TON PIN FREQUENCY (kHz) 300 (as shipped) Not Installed Not Installed Not Installed Floating Installed Not Installed Not Installed Connected to VCC 200 Not Installed Installed Not Installed Connected to REF 450 Not Installed Not Installed Installed Connected to GND 600 Important: Don’t change the operating frequency without first recalculating component values. Frequency has a significant effect on preferred inductor value, peak current-limit level, MOSFET heating, PFM/PWM switchover point, output noise, efficiency, and other critical parameters. Table 5. Jumper JU7 Functions (Output Voltage Selection) JU7 Installed FB PIN Connected to VCC Not Installed Connected to GND through R2 (R1 = open) VOUT = 2.5V Short on R2 Adjustable from 1V to 5.5V Installed Not Installed Connected to resistor-divider R1/R2 OUTPUT VOLTAGE VOUT = 1.8V (default) Refer to the MAX1844 data sheet for information on setting VOUT in adjustable mode. Table 6. Jumper JU8 Functions (Latching/Nonlatching Overvoltage Protection) JU8 LATCH PIN 1 and 2 Connected to VCC 2 and 3 Connected to GND OVP BEHAVIOR Table 7. Jumper JU9 Functions (Undervoltage Protection Selection) JU9 UVP PIN UVP THRESHOLD 1 and 2 Connected to VCC UVP is enabled. UVP threshold is 70% of nominal. 2 and 3 Connected to GND UVP is disabled. Connected to resistor-divider R14/R15 Refer to the MAX1844 data sheet for information on setting UVP in adjustable mode. Not Installed Table 8. Jumper JU10 Functions (Overvoltage Protection Selection) JU10 OVP PIN 1 and 2 Connected to VCC OVP is disabled. 2 and 3 Connected to GND OVP is enabled. OVP threshold is 114.5% of nominal. Nonlatching Latching (default) Not Installed Connected to resistor-divider R13/R11 OVP THRESHOLD Refer to the MAX1844 data sheet for information on setting OVP in adjustable mode. _______________________________________________________________________________________ 3 Evaluates: MAX1844 Table 4. Jumpers JU4, JU5, and JU6 Functions (Switching-Frequency Selection) Evaluates: MAX1844 MAX1844 Evaluation Kit VBIAS +5V C5 4.7µF 10V D2 CMPSH-3 C6 3.3µF 10V R7 20Ω VCC VBATT 7V TO 24V 14 13 16 V+ VDD VCC BST 5 18 N1-B VCC SHDN R9 274kΩ 1% REF SKIP JU1 3 SHDN LX 4 20 19 3 C3 0.1µF 7 JU3 7 U1 VCC MAX1844 JU2 CS 2 12 8 VCC FLOAT = 300kHz 15 JU4 VCC 200KHz OUT 1 R10 0.015Ω 1% R8 200Ω SKIP 6 GND C7 2200pF REF FB VCC JU7 5 VCC TON JU6 600KHz R4 100kΩ JU8 C2 330µF 6.3V R1 OPEN C4 0.22µF JU5 450KHz D1 8 1 R6 1MΩ REF 2V VOUT 1.8V L1 4.7µH N1-A ILIM DL 17 1 2 3 DH R5 1MΩ VCC R3 130kΩ 1% C1 10µF 25V 6 PGOOD 2 10 R2 OPEN PGOOD LATCH VCC R15 OPEN 1 JU9 2 R14 OPEN VCC 9 UVP OVP JU10 1 4 REF R11 OPEN 3 3 R13 OPEN GND 11 2 REF Figure 1. MAX1844 EV Kit Schematic 4 _______________________________________________________________________________________ MAX1844 Evaluation Kit Evaluates: MAX1844 1.0" 1.0" Figure 2. MAX1844 EV Kit Component Placement Guide— Component Side Figure 3. MAX1844 EV Kit PC Board Layout—Component Side 1.0" Figure 4. MAX1844 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ______________________5 © 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.