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MAX1642 EV Kit
8/7/97 5:05 PM
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MAX1642 Evaluation Kit
_______________General Description
The MAX1642 evaluation kit (EV kit) is a step-up switching regulator for one-cell, battery-powered systems. It accepts a positive input between 0.9V and 1.65V and converts it to a 3.3V preset output for currents up to 20mA. The MAX1642 EV kit provides ultra-low quiescent current and high efficiency for maximum battery life. Operation up to 50kHz allows the use of a tiny surface-mount inductor while minimizing interference with sensitive intermediate frequencies in pagers and other RF applications. This EV kit is a fully assembled and tested surfacemount circuit board. Additional pads on the bottom of the board accommodate the external feedback resistors for setting different output voltages. It can also be used to evaluate the MAX1643.
____________________________Features
o 0.9V to 1.65V Input Voltage Range o 3.3V 4% Output Voltage o Adjustable Output Voltage (2V to 5.2V) o 80% Efficiency (VIN = 1.2V, ILOAD = 20mA) o Internal 500mA Synchronous Rectifier o 2A Shutdown Mode (MAX1642) o Low-Battery Detector (MAX1643) o Ultra-Small, 8-Pin MAX Package o Power-Fail Output o Surface-Mount Components o Fully Assembled and Tested
____________________Component List
DESIGNATION QTY C1, C2 C3 C4 JU1 L1 R1, R2, R4 R3, R5 U1 None None 2 1 0 1 1 0 2 1 1 1 DESCRIPTION 22F, 6.3V tantalum capacitors Sprague 595D226X06R3B2T 0.1F ceramic capacitor Open 3-pin header 100H, 520mA inductor Sumida CD54-101 Open 100k, 5% resistors MAX1642EUA (8-pin MAX) Shunt MAX1642/MAX1643 PC board
______________Ordering Information
PART TEMP. RANGE BOARD TYPE MAX1642EVKIT 0C to +70C Surface Mount Note: To evaluate the MAX1643, request a MAX1643EUA free sample with the MAX1642 EV kit.
________________________Quick Start
The MAX1642 EV kit is fully assembled and tested. Follow these steps to verify board operation. Do not turn on the power supply until all connections are completed. 1) Connect a 1V supply voltage to the VIN pad. The ground connects to the GND pad. 2) Connect a voltmeter and load, if any, to the VOUT pad. 3) For normal operation, place the shunt on JU1 across pins 1 and 2. 4) Turn on the power supply to the board and verify that the output voltage is 3.3V.
______________Component Suppliers
SUPPLIER* AVX Coilcraft Coiltronics Dale-Vishay Sprague Sumida Vishay/Vitramon PHONE (803) 946-0690 (847) 639-6400 (561) 241-7876 (402) 564-3131 (603) 224-1961 (847) 956-0666 (203) 268-6261 FAX (803) 626-3123 (847) 639-1469 (561) 241-9339 (402) 563-6418 (603) 224-1430 (847) 956-0702 (203) 452-5670
*Please indicate that you are using the MAX1642 when you contact these suppliers. ________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
MAX1642 EV Kit
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MAX1642 Evaluation Kit Evaluates: MAX1642/MAX1643
_______________Detailed Description
The MAX1642 EV kit provides a 3.3V output from a 0.9V to 1.65V input voltage. It delivers up to 20mA with 80% typical conversion efficiency.
Power-Fail Output
The MAX1642 has an on-chip comparator for power-fail detection. This comparator can be used to detect loss of power at the input or output. The MAX1642 EV kit detects power loss at the input. If the voltage at PFI falls below 614mV 3%, the PFO output sinks current to GND. The power-fail monitor's threshold is set by two resistors: R3 and R4. Refer to the Power-Fail Detection section in the MAX1642 data sheet for instructions on selecting resistors R3 and R4.
Jumper Selection
The 3-pin header JU1 selects shutdown mode. Table 1 lists the selectable jumper options. In shutdown, the internal switching MOSFET turns off, PFO goes into a high-impedance state, and the synchronous rectifier turns off to prevent reverse current from flowing through the output back to the input. However, there is still a forward current path through the synchronousrectifier body diode from the input to the output. Thus, the output doesn't drop lower than a diode drop below the battery voltage. Connect the SHDN pin to VIN for normal operation.
Evaluating the MAX1643
The MAX1642 EV kit can also be used to evaluate the MAX1643. The only modifications required are to replace the MAX1642 with the MAX1643 and remove the shunt from JU1. Refer to the Detailed Description and Pin Description sections of the data sheets for the differences between the MAX1642 and MAX1643.
Table 1. Jumper JU1 Functions
SHUNT LOCATION 1 and 2 2 and 3 SHDN PIN Connected to VIN Connected to GND MAX1642 OUTPUT MAX1642 enabled, VOUT = 3.3V Shutdown mode, VOUT = VIN - VDIODE
Evaluating Other Output Voltages
The MAX1642 is preset for a 3.3V output voltage. However, its output can be adjusted via an external voltage divider formed by R1 and R2 (located on the bottom of the board). The only other modification required is to cut the trace across R2. Since FB leakage is 10nA max, select feedback resistor R2 in the 100k to 1M range. R1 is given by the following equation: V R1 = R2 OUT - 1 VREF where VREF = 1.23V (the internal reference voltage).
2
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MAX1642 EV Kit
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MAX1642 Evaluation Kit
L1 100H
VIN C1 22F 6.3V SHDN 3 VIN
1
BATT
LX
7
C3 0.1F 1 2 JU1 4 SHDN OUT 8 C4 OPEN FB 5 R2 SHORT C2 22F 6.3V VOUT 3.3V R1 OPEN
U1 MAX1642
2 PFI
R3 100k 6 R4 OPEN 3 R5 100k
GND
PFO
PFO
Figure 1. MAX1642 EV Kit Schematic
_______________________________________________________________________________________
3
MAX1642 EV Kit
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MAX1642 Evaluation Kit Evaluates: MAX1642/MAX1643
1.0"
Figure 2. MAX1642 EV Kit Component Placement Guide-- Component Side
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Figure 3. MAX1642 EV Kit Component Placement Guide-- Solder Side
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Figure 4. MAX1642 EV Kit PC Board Layout--Component Side
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Figure 5. MAX1642 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) 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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