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19-1905; Rev 0; 1/01
MAX1791 Evaluation Kit
General Description
The MAX1791 evaluation kit (EV kit) demonstrates a standard 2A 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, I/O, and other low-voltage supplies in notebook computers and PDAs. The MAX1791 EV kit provides a 3.3V output voltage from a +5V to +20V battery input range. It delivers up to 2A 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 1.25V to 5.5V range by changing feedback resistors R1 and R2. This EV kit can also be used to evaluate the MAX1762 (1.8V or 2.5V output voltage). o No Current-Sense Resistor o +5V to +20V Input Voltage Range o 3.3V or 5V Preset Output Voltage (MAX1791) o 1.8V or 2.5V Preset Output Voltage (MAX1762) o Adjustable Output Voltage (1.25V to 5.5V, External Divider) o 2A Output Current o 300kHz Switching Frequency o 5A IC Shutdown Current o 10-Pin MAX Package o Low-Profile Components o Surface-Mount Construction o Fully Assembled and Tested
Features
Evaluates: MAX1791/MAX1762
Component List
DESIGNATION QTY DESCRIPTION 10F, 25V ceramic capacitor (1812) Taiyo Yuden TMK432BJ106KM or TDK C4532X5R1E106M 220F, 10V low-ESR 40m capacitor Sanyo 10TPB220M 0.1F ceramic capacitor (1206) 1F, 16V ceramic capacitor (1206) Taiyo Yuden EMK316BJ105KL or TDK C3216X7R1C105M Not installed (1206) 7H power inductor Sumida CDRH104R-7R0NC Dual N- and P-channel MOSFETs Fairchild FDS8958A Not installed (1206) MAX1791EUB (10-pin MAX) 3-pin headers Shunts MAX1791 PC board MAX1791 data sheet MAX1791EVKIT data sheet
Ordering Information
PART MAX1791EVKIT TEMP. RANGE 0C to +70C IC PACKAGE 10 MAX
C1
1
Note: To evaluate the MAX1762, request a MAX1762EUB free sample with the MAX1791 EV kit.
C2 C3
1
Component Suppliers
SUPPLIER Coilcraft Coiltronics Fairchild International Rectifier Sanyo Sumida Taiyo Yuden TDK PHONE 708-639-6400 561-241-7876 408-721-2181 310-322-3331 619-661-6835 708-956-0666 408-573-4150 847-390-4373 FAX 708-639-1469 561-241-9339 408-721-1635 310-322-3332 619-661-1055 708-956-0702 408-573-4159 847-390-4428
1
C4
1
C5 L1 N1, P1 R1, R2, R3 U1 JU1, JU2 None None None None
0 1 1 0 1 2 2 1 1 1
Note: Please indicate that you are using the MAX1791/ MAX1762 when contacting these component suppliers.
________________________________________________________________ Maxim Integrated Products
1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
MAX1791 Evaluation Kit Evaluates: MAX1791/MAX1762
Quick Start
The MAX1791 EV kit is a fully assembled and tested surface-mount board. Follow the steps below to verify board operation. Do not turn on the power supply until all connections are completed: 1) Connect a voltmeter and load (if any) to the VOUT pad. 2) Verify that the shunts are across JU1 pins 1 and 2 and JU2 pins 2 and 3. 3) Connect a +5V to +20V supply to the pads marked VIN and GND. 4) Turn on the power and verify that the output voltage is 3.3V. 5) See the Output Voltage Selection section to modify the board for a different output voltage.
Table 1. Jumper JU1 Functions (Shutdown Mode)
SHUNT LOCATION 1, 2 2, 3 SHDN PIN Connected to VIN Connected to GND MAX1791 OUTPUT MAX1791 enabled, VOUT = 3.3V Shutdown mode, VOUT = 0
Table 2. Jumper JU2 Functions (Output Voltage)
SHUNT LOCATION 1, 2 2, 3 FB PIN Connected to VL Connected to GND OUTPUT VOLTAGE VOUT = 5.0V VOUT = 3.3V
Detailed Description
Jumper Selections
The MAX1791 EV kit features a shutdown mode that reduces quiescent current to less than 5A to preserve battery life.
Output Voltage Selection
The MAX1791 is initially set for a 3.3V output by connecting the FB pin to GND or 5V by connecting the FB pin to VL. However, by adding external resistors R1 and R2, the output can be adjustable from 1.25V to 5.5V. Remove the shunt from jumper JU2, and install output voltage-divider resistors R1 and R2. Refer to the Setting the Output Voltage section of the MAX1791 data sheet regarding how to extend the output voltage range from 0.5V to 5.5V and instructions on how to calculate the values for R1 and R2.
2
_______________________________________________________________________________________
VIN +5V TO +20V
R4 SHORT C6 OPEN C1 10F 25V
GND VIN 10
1 JU1 2
Figure 1. MAX1791 EV Kit Schematic
5 SHDN P1 5 8 R5 SHORT 6 DH 9 4 3 VP
3
SHDN
L1 7H
VOUT +3.3V AT 2A
CS 2 REF R6 OPEN C3 0.1F
U1 MAX1791
7 7 1 6 2 N1 8 1 VL DL C4 1.0F GND
C2 220F 10V
GND
VL +5V
OUT
4 C5 OPEN
R3 SHORT
VL
R1 OPEN
FB
3
1 2 JU2 3
Evaluates: MAX1791/MAX1762
_______________________________________________________________________________________
R2 OPEN
MAX1791 Evaluation Kit
3
MAX1791 Evaluation Kit Evaluates: MAX1791/MAX1762
1.0"
Figure 2. MAX1791 EV Kit Component Placement Guide-- Component Side
1.0"
Figure 3. MAX1791 EV Kit Component Placement Guide-- Solder Side
1.0"
Figure 4. MAX1791 EV Kit PC Board Layout--Component Side
1.0"
Figure 5. MAX1791 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.
4 _____________________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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