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19-2613; Rev 0; 10/02
MAX1858 Evaluation Kit
General Description
The MAX1858 evaluation kit (EV kit) demonstrates the MAX1858's standard application circuit. This dual PWM synchronous DC-to-DC converter generates outputs down to 0.75V for core, I/O, and logic supplies. The MAX1858 EV kit provides dual 1.8V and 2.5V output voltages from an 8V to 20V input voltage range. It delivers up to 10A output current for the 2.5V output and 10A for the 1.8V output with greater than 90% efficiency. Both converters operate 180 degrees out-of-phase to reduce input ripple current. The EV kit operates at 600kHz switching frequency and has superior line- and loadtransient response. This EV kit is a fully assembled and tested circuit board. It allows evaluation of other output voltages in the 0.75V to 15V range. The MAX1858 EV kit can also be used to evaluate the MAX1875 and MAX1876. o 8V to 20V Input Voltage Range o 1.8V and 2.5V Adjustable Output Voltages o 10A Output Current (2.5V Output) o 10A Output Current (1.8V Output) o Lossless Foldback Current Limit o 600kHz Switching Frequency o RST Output with 140ms Delay o 180 Degrees Out-of-Phase Operation o 24-Pin QSOP Package o Low-Profile Components o Fully Assembled and Tested
Features
Evaluates: MAX1858/MAX1875/MAX1876
Ordering Information
PART MAX1858EVKIT TEMP RANGE 0C to +70C IC PACKAGE 24 QSOP
Component List
DESIGNATION C1-C4 C5, C6, C22 C7 C8 C9-C16 C17, C18 QTY 4 3 1 1 8 2 DESCRIPTION 10F, 25V ceramic capacitors (1812) Taiyo Yuden TMK432BJ106KM or TDK C4532X5R1E106M 0.1F ceramic capacitors (0805) 0.01F ceramic capacitor (0805) 0.0068F ceramic capacitor (0805) 220F, 4V, 40m low-ESR capacitors Sanyo 4TPC220M 100pF ceramic capacitors (0805) 0.22F, 16V X5R ceramic capacitor (0805) Taiyo Yuden EMK212BJ224KG or TDK2012X7R1H224KT 4.7F, 10V X5R ceramic capacitor (1206) Taiyo Yuden LMK316BJ475ML 0.22F, 50V X7R ceramic capacitor (0805) Taiyo Yuden UMK212BJ224MG or TDK C2012X7R1H224M 100mA, 30V dual Schottky diode Central Semiconductor CMPSH-3A 3A, 30V Schottky diodes Nihon EC31QS03L 100mA, 30V Schottky diodes Central Semiconductor CMSSH-3 N1-N4 R1 R2, R4, R5 R3 R6 R7 R8 R9 R10 R11 R12, R13 R14 R15 None U1 None DESIGNATION JU1, JU2 L1, L2 QTY DESCRIPTION 2 3-pin headers 1.1H power inductors 2 Sumida CEP12D38-H-1R1 (18.1A, 6m, 12.5mm x 12.5mm x 4.0mm) N-channel MOSFETs 8-pin SO 4 International Rectifier IRF7811W or Fairchild FDS6694 1 8.06k 1% resistor (0805) 3 1 1 1 1 1 1 1 2 1 1 2 1 1 10k 1% resistors (0805) 15k 1% resistor (0805) 8.2k 5% resistor (0805) 5.9k 5% resistor (0805) 97.6k 1% resistor (0805) 140k 1% resistor (0805) 100k 5% resistor (0805) 4.7 5% resistor (0805) 4.7 5% resistors (0603) 118k 1% resistor (0805) 84.5k 1% resistor (0805) Shunts MAX1858EEG 24-pin QSOP MAX1858 PC board
C19
1
C20
1
C21
1
D1 D2, D3 D4, D5
1 2 2
________________________________________________________________ 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.
MAX1858 Evaluation Kit Evaluates: MAX1858/MAX1875/MAX1876
Component Suppliers
SUPPLIER Central Semiconductor Fairchild International Rectifier Nihon Sanyo Sumida Taiyo Yuden TDK PHONE 516-435-1110 408-721-2181 310-322-3331 847-843-7500 619-661-6835 708-956-0666 408-573-4150 847-390-4373 FAX 516-435-1824 408-721-1635 310-322-3332 847-843-2798 619-661-1055 708-956-0702 408-573-4159 847-390-4428 WEBSITE www.centralsemi.com www.fairchildsemi.com www.irf.com www.niec.co.jp www.sanyovideo.com www.sumida.com www.t-yuden.com www.component.tdk.com
Note: Please indicate that you are using the MAX1858 when contacting these component suppliers.
_________________________Quick Start
The following equipment is required before beginning: * 8V to 20V power supply * Electronic loads capable of sinking 10A each * Digital multimeters (DMMs) * 100MHz dual-trace oscilloscope Follow these steps to verify board operation. Do not turn on the power supply until all connections are completed: 1) Ensure that the circuit is connected correctly to the supply and electronic loads before applying any power. Set the electronic loads in resistive mode. 2) Verify that the shunts are across JU1 pins 1 and 2 and JU2 pins 1 and 2. 3) Turn on power supply. 4) Verify that the output voltages are 1.8V and 2.5V.
Evaluating Other Output Voltages
The EV kit outputs are programmed for 1.8V and 2.5V. However, the output voltages can also be adjusted between 1V and 15V by selecting R1/R2 and R3/R4 values. Select feedback resistors R2 and R4. R1 and R3 are then given by: R1 (or R3) = R2 (or R4) x [(VOUT / VFB) - 1] where VFB = 1V. Refer to the MAX1858 data sheet for selection of output capacitors, inductors, and compensation networks. For output voltages below 1V, refer to Figure 6 in the MAX1858 data sheet.
Evaluating MAX1875/MAX1876
Replace U1 with the MAX1875/MAX1876.
Table 1. JU1 Functions (EN Mode Selection)
JU1 1 and 2 2 and 3 Not Installed EN PIN Connected to VL Connected to GND Connected to EN pad MAX1858 OUTPUT MAX1858 enabled, VOUT1 = 1.8V and VOUT2 = 2.5V Shutdown mode, VOUT1 = 0V and VOUT2 = 0V MAX1858 must be enabled by an external signal
Table 2. JU2 Functions (SYNC Mode Selection)
JU2 1 and 2 SYNC PIN Connected to VL EFFECT Used to sync up an additional MAX1858. CKO is 2x DH1 and phase shifted by 90 degrees. Used to sync up an additional single buck. CKO is the same frequency and phase as DH1. External clock is applied to SYNC input (1100kHz to 1300kHz)
2 and 3
Connected to GND Connected to SYNC pad
Not Installed
2
_______________________________________________________________________________________
BST1 BST2 1 L D1 VL 3 VL 5V VIN 87 65 C3 10F 25V C4 10F 25V C21 0.22F 50V C22 0.1F 5 V+ 4 14 BST1 16 BST1 LXI 87 5 D3 4 DL1 1 3 U1 11 D4 12 C7 0.01F R7 5.9k 13 RST VL 1 2 JU1 24 EN REF 6 C19 0.22F VL 3 9 SYNC ILIM1 8 CKO R5 10k 1% 4 OSC 1 2 JU2 3 VOUT1 C17 100pF C18 100pF COMP1 COMP2 1 R6 8.2k R2 10k 1% FB1 D5 R4 10k 1% C8 0.0068F MAX1858 FB2 2 2 R3 15k 1% GND PGND DL2 4 1 3 2 18 7 17 20 N4 6 L2 1.1H LX2 R13 22 4.7 C6 0.1F 3 21 BST2 R12 4.7 15 21 C5 0.1F 7 8 N3 D2 R1 8.06k 1% VL 6 5 DH1 BST2 VOUT2 2.5V DH2 1 3 2 23 4 N2 19 VL C20 4.7F 10V R11 4.7 C1 10F 25V C2 10F 25V 7 8 N1 6 5 R 2
Figure 1. MAX1858 EV Kit Schematic
L1 1.1H C15 C16 C13 C14 220F 220F 220F 220F 4V 4V 4V 4V 10 VOUT2 R14 118k 1% ILIM2 3 R8 97.6k 1% R15 84.5k 1% R9 140k 1%
VIN
GND
VOUT1 1.8V
C11 C12 C9 C10 220F 220F 220F 220F 4V 4V 4V 4V
R10 100k
RST
EN
SYNC
Evaluates: MAX1858/MAX1875/MAX1876
_______________________________________________________________________________________
CKO
MAX1858 Evaluation Kit
3
MAX1858 Evaluation Kit Evaluates: MAX1858/MAX1875/MAX1876
Figure 2. MAX1858 EV Kit Component Placement Guide--Top Silkscreen
Figure 3. MAX1858 EV Kit PC Board Layout--Component Side
4
_______________________________________________________________________________________
MAX1858 Evaluation Kit Evaluates: MAX1858/MAX1875/MAX1876
Figure 4. MAX1858 EV Kit PC Board Layout--Ground Layer 2
Figure 5. MAX1858 EV Kit PC Board Layout--Ground Layer 3
_______________________________________________________________________________________
5
MAX1858 Evaluation Kit Evaluates: MAX1858 MAX1875/MAX1876
Figure 6. MAX1858 EV Kit PC Board Layout--Solder Side
Figure 7. MAX1858 EV Kit Component Placement Guide-- Bottom Silkscreen
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) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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