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19-1426; Rev 0; 2/99
MAX1688 Evaluation Kit
General Description
The MAX1688 evaluation kit (EV kit) is a boost switching regulator for one Li-Ion cell or three NiCd/NiMH cells in battery-powered systems. The EV kit accepts a positive input between 2.7V and 6V and converts it to a 5V output. It can easily deliver the current burst required for cell-phone power amplifier systems. The MAX1688 reduces battery surge current by slowly charging a reservoir capacitor, which supplies the necessary peak energy for the current burst. As a result, the peak battery input current is limited, thereby minimizing the battery voltage sag and transient dips. The EV kit operates at 600kHz, allowing the use of small external components. The MAX1688 EV kit provides low quiescent current and high efficiency for maximum battery life. An internal synchronous rectifier is used to provide over 90% conversion efficiency. This EV kit is a fully assembled and tested surface-mount circuit board. The MAX1688 EV kit can also be used to evaluate the MAX1687. o 2.7V to 6V Input Voltage Range o 5V Output Voltage o Less than 500mV Output Voltage Droop with 1.42A Burst Current o 90% Efficiency o Output Disconnected from Input during Shutdown o 600kHz Switching Frequency o Internal MOSFET and Synchronous Rectifier o 3A IC Shutdown Current o Surface-Mount Components (TSSOP Package) o Fully Assembled and Tested
Features
Evaluates: MAX1687/MAX1688
Component List
DESIGNATION QTY C1 C2 C3, C4 C5 L1 R1 R2, R3 R4 R5 U1 None None 1 1 2 0 1 1 2 1 0 1 1 1 DESCRIPTION 47F, 16V tantalum capacitor AVX TPSC476M016R0350 or Sprague 595D476X0016C2T 0.1F ceramic capacitor 1000F, 6.3V electrolytic capacitors* Sanyo 6CV1000AX Not installed 10H inductor Sumida CLS62B-100 or Coiltronics TP2-100 60.4k 1% resistor 20.0k 1% resistors 1M 5% resistor Not installed (for MAX1687 only) MAX1688EUE MAX1688 PC board MAX1688 data sheet PART
Ordering Information
TEMP. RANGE IC PACKAGE MAX1688EVKIT 0C to +70C 16 TSSOP Note: To evaluate the MAX1687, order a MAX1687EUE sample with the MAX1688 EV kit.
Quick Start
The MAX1688 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 3V supply voltage to the VIN pad. Connect the supply ground to the GND pad. 2) Connect a voltmeter and load, if any, to the VOUT pad. 3) Turn on the power supply. 4) Synchronize the GSM pulse load to the ON signal by applying the logic signal that controls the power amplifier to the ON/OFF pad. ON is low when GSM load is applied. 5) Verify the output voltage is 5V. For other output voltages, refer to the Adjusting the Output Voltage section in the MAX1687/MAX1688 data sheet for instructions on selecting the feedback resistors.
*For low-profile applications, use Sprague tantalum 595108X06R3R2.
Component Suppliers
SUPPLIER AVX Coiltronics Dale-Vishay Sanyo Sprague Sumida PHONE 803-946-0690 561-241-7876 402-564-3131 619-661-6835 603-224-1961 708-956-0666 FAX 803-626-3123 561-241-9339 402-563-6418 619-661-1055 603-224-1430 708-956-0702
Patent pending
________________________________________________________________ Maxim Integrated Products
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For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769.
MAX1688 Evaluation Kit Evaluates: MAX1687/MAX1688
Detailed Description
The MAX1688 EV kit is designed for supplying short-duration, high-current bursts for GSM cell phone applications. It combines a boost switching regulator, an N-channel power MOSFET, a P-channel synchronous rectifier, and a precision reference in a single, tiny 16-pin TSSOP package. The EV kit accepts a positive input between 2.7V and 6V and converts it to a 5V output with less than 500mV output voltage droop at 1.4A burst load. The EV kit operates at 600kHz, allowing the use of small external components. For other applications including component value selection, refer to the Applications Information section in the MAX1687/MAX1688 data sheet.
Evaluating the MAX1687
The MAX1688 EV kit can also be used to evaluate the MAX1687. Follow the steps below to evaluate the MAX1687. 1) Replace the MAX1688 with a MAX1687EUE. 2) Install a short at location JU1 to run the MAX1687 continuously or apply a logic signal for ON/OFF control. 3) Turn on the power supply. 4) Set up the voltage to the MAX1687's LIM pad by applying an external voltage to the CHG(LIM) pad or by completing the voltage divider (R3/R5). Refer to the Adjusting Current Limit (MAX1687) section of the MAX1687/MAX1688 data sheet.
L1 10H
3 4 VIN 2.7V TO 6V 1 C1 47F 16V C2 0.1F 2
LX1 LX1
LX2 LX2
13 14 15 C3 1000F 6.3V C4 1000F 6.3V C5 OPEN VOUT 5.0V
U1
IN IN OUT
MAX1688 (MAX1687)
OUT 16
CHG (LIM) R3 20k 1% R5 OPEN
5 7
R1 60.4k 1%
CHG (LIM) FB REF NC
6 R2 20k 1%
8
ON/OFF VIN JU1 R4 1M
9 10
ON AGND
PGND
12
PGND
11
Figure 1. MAX1688 EV Kit Schematic
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MAX1688 Evaluation Kit Evaluates: MAX1687/MAX1688
1.0"
Figure 2. MAX1688 EV Kit Component Placement Guide-- Component Side
1.0"
Figure 3. MAX1688 EV Kit PC Board Layout--Component Side
1.0"
Figure 4. MAX1688 EV Kit PC Board Layout--Solder Side
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MAX1688 Evaluation Kit Evaluates: MAX1687/MAX1688
NOTES
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) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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