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19-2101; Rev 0; 8/01
MAX1845 Evaluation Kit
General Description
The MAX1845 evaluation kit (EV kit) demonstrates the MAX1845's standard application circuit. This DC-DC converter steps down high-voltage batteries and/or AC adapters, generating precision, low-voltage rails for use as chipset, DRAM supplies, CPU core, and IO supplies. The MAX1845 EV kit provides dual 1.8V and 2.5V output voltages from a 7V to 22V battery input range. It delivers up to 4A output current for the 2.5V output and 7A for the 1.8V output, with greater than 90% efficiency. The EV kit operates at 255kHz/345kHz 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-R4. o 7V to 22V Input Voltage Range o 1.8V and 2.5V Output Voltages o 1.0V to 5.5V Adjustable Outputs o 4A Output Current (2.5V Output) o 7A Output Current (1.8V Output) o Adjustable Current-Limit Threshold o 255kHz/345kHz Switching Frequency o Power-Good Output o Over- and Undervoltage Protection o 28-Pin QSOP Package o Low-Profile Components o Fully Assembled and Tested
Features
Evaluates: MAX1845
Ordering Information
PART MAX1845EVKIT TEMP. RANGE 0oC to +70oC IC PACKAGE 28 QSOP
Component List
DESIGNATION C1-C5 QTY 5 DESCRIPTION 10F, 25V ceramic capacitors (1812) Taiyo Yuden TMK432BJ106KM or TDK C4532X5R1E106M 470F, 6.3V, 30m low-ESR tantalum capacitors Kemet T510X477M006AS 0.1F ceramic capacitors (0805) 1F, 10V X5R ceramic capacitor (0805) Taiyo Yuden LMK212BJ105MG 3.3F, 10V X5R ceramic capacitor (1206) Taiyo Yuden LMK316BJ335ML Not installed 0.22F ceramic capacitor (1206) 4.7F, 16V tantalum capacitor Sprague 595D475X0016A2B 100mA, 30V dual Schottky diode Central Semiconductor CMPSH-3A 1A, 30V Schottky diodes Nihon EP10QY03 or Toshiba CRS02 2.2H power inductor Panasonic ETQP6F2R2SFA or Sumida CDRH127-2R4 DESIGNATION L2 N1 QTY 1 1 DESCRIPTION 4.7H power inductor Sumida CDRH124-4R7MC N-channel MOSFET International Rectifier IRF7807 or Fairchild FDS6612A N-channel MOSFET International Rectifier IRF7805 or Fairchild FDS6670A Dual N-channel MOSFET Fairchild FDS6982A Not installed 0.005 1%, 1W resistor (2512) Dale WSL-2512-R005F or Panasonic ERJM1WSF5MOU 100k 5% resistor (0805) 1M 5% resistors (0805) 0.010 1%, 1/2W resistor (2010) Dale WSL-2010-R010F 10 5% resistor (0805) MAX1845EEI (28-pin QSOP) 3-pin headers Shunts Rubber feet MAX1845 PC board MAX1845 data sheet MAX1845EVKIT data sheet
C6-C9 C10, C11 C12
4 2 1
N2 N3A, N3B R1-R4, R7, R8, R10-R14 R5 R6 R9, R15 R19 R20 U1 JU1, JU2, JU3 None None None None None
1 1 0 1 1 2 1 1 1 3 3 4 1 1 1
C13 C14, C15, C17, C18 C16 C19 D1 D2, D3
1 0 1 1 1 2
L1
1
________________________________________________________________ Maxim Integrated Products
1
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.
MAX1845 Evaluation Kit Evaluates: MAX1845
Component Suppliers
SUPPLIER Central Semiconductor Dale-Vishay Fairchild International Rectifier Kemet Nihon Panasonic Sumida Taiyo Yuden TDK Toshiba PHONE 516-435-1110 402-564-3131 408-721-2181 310-322-3331 408-986-0424 847-843-7500 714-373-7939 708-956-0666 408-573-4150 847-390-4373 949-455-2000 FAX 516-435-1824 402-563-6418 408-721-1635 310-322-3332 408-986-1442 847-843-2798 714-373-7183 708-956-0702 408-573-4159 847-390-4428 949-859-3963 2 and 3
Table 1. Jumper JU1 Functions (Output Voltage VOUT1 Control)
JU1 1 and 2 2 and 3 ON1 PIN Connected to VCC Connected to GND OUTPUT VOLTAGE VOUT1 = 1.8V, enabled VOUT1 = 0V, disabled
Table 2. Jumper JU2 Functions (Output Voltage VOUT2 Control)
JU2 1 and 2 ON2 PIN Connected to VCC Connected to GND OUTPUT VOLTAGE VOUT2 = 2.5V, enabled VOUT2 = 0V, disabled
Note: Please indicate that you are using the MAX1845 when contacting these component suppliers.
Recommended Equipment
* * * * * 7V to 22V, power supply, battery, or notebook AC adapter DC bias power supply, 5V at 100mA Dummy loads capable of sinking 4A and 7A Digital multimeters (DMMs) 100MHz dual-trace oscilloscope
Table 3. Jumper JU3 Functions (SKIP Mode Selection)
JU3 SKIP PIN Connected to VCC OPERATING 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.
1 and 2
Quick Start
1) Ensure that the circuit is connected correctly to the supplies and dummy load prior to applying any power. 2) Verify that the shunts are across JU1 pins 1 and 2, JU2 pins 1 and 2, and JU3 pins 1 and 2. 3) Turn on VIN supply prior to +5V bias power; otherwise, the output UVLO timer will time out and the FAULT latch will be set, disabling the regulator outputs until +5V power is cycled or ON1/ON2 is toggled. 4) Verify that the output voltages are 1.8V (VOUT1) and 2.5V (VOUT2).
2 and 3 Connected to GND
Table 4. Jumper JU4 Functions (Output Voltage Selection)
JU4 1 and 2 2 and 3 FB1 PIN Connected to VCC Connected to GND (PC board trace) Connected to resistor-divider R3/R4 OUTPUT VOLTAGE VOUT1 = 1.5V VOUT1 = 1.8V
Evaluating Other Output Voltages
The EV kit outputs are preset to +1.8V and +2.5V. However, the output voltages can also be adjusted between 1.0V and 5.5V by selecting R1/R2 and R3/R4 values. Select feedback resistors R2 (or R4) in the 5k to 50k range. R1 (or R3) is then given by: R1 (or R3) = R2 (or R4) x [(VOUT / VFB) - 1] where VFB = 1.0V.
Not installed
Adjustable mode
2
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MAX1845 Evaluation Kit Evaluates: MAX1845
Table 5. Jumpers JU5/JU6/JU7 Functions (Switching-Frequency Selection)
JU5 Not installed Not installed Installed Not installed JU6 Not installed Installed Not installed Not installed JU7 Not installed Not installed Not installed Installed TON PIN Floating Connected to VCC Connected to REF Connected to GND VOUT1/VOUT2 FREQUENCY (kHz) 255/345 (as shipped) 170/235 355/485 460/620
IMPORTANT: Don't change the operating frequency without first recalculating component values because the frequency has a significant effect on the peak current-limit level, MOSFET heating, preferred inductor value, PFM/PWM switchover point, output noise, efficiency, and other critical parameters.
Table 6. Jumper JU8 Functions (Overvoltage Protection Selection)
JU8 Installed Not installed OVP PIN Connected to VCC Connected to GND through R9 Connected to voltage between 1.0V and 1.8V through REF divider R9, R10 OVP THRESHOLD OVP is disabled OVP is enabled. OVP threshold is 114% of nominal. OVP threshold set to 100% to 180% of nominal VOUT1 and VOUT2 according to divider R9, R10
Table 7. Jumper JU9 Functions (Undervoltage Protection Selection)
JU9 Not installed Installed UVP PIN Connected to VCC through R15 Connected to GND UVP THRESHOLD UVP is enabled. UVP threshold is 70% of nominal. UVP is disabled
Not installed
Table 8. Jumper JU10 Functions (Fixed/Adjustable Current-Limit Selection for VOUT2)
JU10 ILIM2 PIN Connected to VCC through a PC board trace Connected to REF through resistordivider R13/R14. Refer to the CurrentLimit Circuit section in the MAX1845 data sheet for information on selecting R13/R14. CURRENT-LIMIT THRESHOLD 50mV (default)
Table 9. Jumper JU11 Functions (Fixed/Adjustable Current-Limit Selection for VOUT1)
JU11 ILIM1 PIN Connected to VCC through a PC board trace Connected to REF through resistordivider R11/R12. Refer to the Current-Limit Circuit section in the MAX1845 data sheet for information on selecting R11/R12. CURRENT-LIMIT THRESHOLD 50mV (default)
SHORT
SHORT
OPEN
Adjustable between 30mV and 250mV
OPEN
Adjustable between 30mV and 250mV
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3
Evaluates: MAX1845
ILIM1 4 V+ C13 3.3F BST1 5 6 N3-B 3 L2 4.7H 4 C11 0.1F 7 4 DL1 CS1 1 28 R5 0.005 1% CS2 15 C15 OPEN 14 7 R6 100k JU2 12 ON2 SKIP 10 REF C16 0.22F FLOAT = 300kHz TON JU6 200kHz JU7 540kHz VCC R15 1M JU1 11 ON1 UVP 9 JU9 1 2 3 5 OVP GND 6 VCC 23 JU8 8 VCC R9 1M R10 OPEN REF PGOOD VCC R8 SHORT (PC TRACE) 16 1 24 DL2 20 2 19 18 17 2 8 7 N1 4 DH1 BST2 DH2 LX2 BST1 LX1 1 BST1 C10 0.1F 27 5 6 25 26 3 2 L1 2.2H C4 10F 25V 5 6 VCC C5 10F 25V 1 VDD 22 L R
MAX1845 Evaluation Kit
Figure 1. MAX1845 EV Kit Schematic
REF JU10 VCC R11 OPEN R14 OPEN 3 3 VCC D1 ILIM2 C3 10F 25V 13 21 R20 10 C12 1F 10V C19 4.7F 16V VBIAS +5V R13 OPEN VCC R12 OPEN JU11 VIN VOUT2 2.5V, 4A D2 C9 470F 6.3V 8 N3-A R19 0.01 1% D3 3 2 8 7 N2
4
U1
1 OUT1 OUT2 C14 OPEN FB2 2 VCC 1 2 3 VOUT1 1.5V 1.8V VCC JU5 420kHz REF 2V FB1 PGOOD R7 SHORT (PC TRACE)
VIN
7V TO 22V
C1 10F 25V
C2 10F 25V
VOUT1 1.8V, 7A
C6 470F 6.3V
C8 470F 6.3V
C7 470F 6.3V
MAX1845
GND 1 2 JU4 3
R3 OPEN
VCC
R1 OPEN
C17 OPEN ON2
R4 OPEN
R2 SHORT (PC TRACE)
C18 OPEN
1 2 JU3 3
JU4
1, 2
2, 3
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ON1
MAX1845 Evaluation Kit Evaluates: MAX1845
Figure 2. MAX1845 EV Kit Component Placement Guide--Component Side
Figure 3. MAX1845 EV Kit PC Board Layout--Component Side
Figure 4. MAX1845 EV Kit PC Board Layout--Internal GND Plane (Layer 2)
Figure 5. MAX1845 EV Kit PC Board Layout--Internal GND Plane (Layer 3)
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5
MAX1845 Evaluation Kit Evaluates: MAX1845
Figure 6. MAX1845 EV Kit PC Board Layout--Solder Side
Figure 7. MAX1845 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 (c) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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