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19-1214; Rev 1; 1/98
MAX1620 Evaluation Kit
General Description
The MAX1620 evaluation kit (EV kit) converts a +1.8V to +12V battery voltage to a +12.5V to +23.5V LCD backplane bias voltage for currents up to 20mA. Both the MAX1620 and MAX1621 include a 5-bit DAC, allowing digital software control of the bias voltage. The MAX1620 uses up/down digital signaling to adjust the DAC, and the MAX1621 uses the System Management Bus (SMBusTM) 2-wire serial interface. The MAX1620 EV kit is a fully assembled and tested surface-mount circuit board. It can also be used to evaluate the MAX1621. o +1.8V to +12V Battery Input Voltage o +12.5V to +23.5V Adjustable Output o 20mA Output o 32-Level Internal DAC o 10A Shutdown Current o Surface-Mount Components o Fully Assembled and Tested
Features
Evaluates: MAX1620/MAX1621
Ordering Information
PART MAX1620EVKIT TEMP. RANGE 0C to +70C BOARD TYPE Surface Mount
Component List
DESIGNATION C1, C6 C2, C3 C5 D1 D4 L1 N1 Q1 R1 R2, R8, R9, R10 R3, R4 R5 R6, R7 R11 U1 JU3 None JU8 None QTY 2 2 1 1 1 1 1 1 1 4 2 1 2 1 1 1 1 1 1 DESCRIPTION 22F, 35V tantalum capacitors AVX TPSE226M035R0300 or Sprague 593D226X0035E2T 0.1F ceramic capacitors 100pF ceramic capacitor Schottky diode Motorola MBR0540T1 Schottky diode Central Semiconductor CMPSH-3 100H inductor Sumida CD54-101 N-channel MOSFET Motorola MMFT3055VL 2N2907A transistor Central Semiconductor CMPT2907A 82k, 5% resistor 100k, 5% resistors 300k, 5% resistors 2.2M, 5% resistor 56k, 5% resistors 10k, 5% resistor MAX1620EEE (QSOP-16) 3-pin header Shunt (JU3) 2-pin header MAX1620/MAX1621 PC board
Note: To evaluate the MAX1621, request a free MAX1621EEE sample with the MAX1620 EV kit.
Component Suppliers
SUPPLIER* AVX Central Semiconductor Coilcraft Coiltronics Dale-Vishay Motorola Sprague Sumida Vishay/Vitramon PHONE 803-946-0690 516-435-1110 847-639-6400 561-241-7876 402-564-3131 602-303-5454 603-224-1961 847-956-0666 203-268-6261 FAX 803-626-3123 516-435-1824 847-639-1469 561-241-9339 402-563-6418 602-994-6430 603-224-1430 847-956-0702 203-452-5670
* Please indicate that you are using the MAX1620 EV kit when contacting these component suppliers.
Quick Start
The MAX1620 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 +1.8V to +12V power supply to the VBATT pad and a +3V to +5.5V supply to the VIN pad. Connect ground to the GND pad. 2) Connect a voltmeter and load, if any, to the VOUT pad. 3) Verify the JU3 shunt is across pins 1 and 2 (positive output). 4) Turn on the power supply and verify that the output voltage is typically +17.8V. 5) For other output voltages, refer to the Output Adjustment section in the MAX1620/MAX1621 data sheet for instructions on selecting the feedback resistors.
1
None 1 MAX1620/MAX1621 data sheet Additional components for negative output (included in 1 Shunt the EV kit) but not installed: C4 1 1F ceramic capacitor C7 D2, D3 1 2 22F, 35V tantalum capacitor AVX TPSE226M035R0300 or Sprague 593D226X0035E2T Schottky diodes Motorola MBR0540T1
SMBus is a trademark of Intel Corp.
________________________________________________________________ Maxim Integrated Products
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.
MAX1620 Evaluation Kit Evaluates: MAX1620/MAX1621
_______________Detailed Description
The MAX1620 EV kit converts a +1.8V to +12V battery voltage to a +12.5V to +23.5V LCD backplane bias voltage for currents up to 20mA. The output voltage can be adjusted with the on-chip DAC, allowing digital software control of the bias voltage. Up/down digital signaling adjusts the DAC.
Table 1. Jumper JU8 Settings
SHUNT LOCATION On Off SHDN PIN Connected to GND Connected to VIN MAX1620 OUTPUT Shutdown mode, VOUT = VBATT, VOUTSW = float MAX1620 enabled, VOUT = +17.8V
Output Voltage Control
The output voltage is set with a voltage divider to the feedback pin (FB). It can be adjusted with an internal DAC summing current into FB through an external resistor. The 5-bit DAC is controlled with a user-programmable up/down counter. The MAX1620 controls the DAC counter with the UP and DN pins. A rising edge on UP increases the output voltage; a rising edge on DN decreases the output voltage. Holding both UP and DN high resets the output voltage to mid-range. Refer to the Output Voltage Control section in the MAX1620/MAX1621 data sheet for more information on controlling the MAX1620/MAX1621 output voltage.
Negative Output Voltage If a negative output voltage is desired, connect the MAX1620's POL pin to ground using jumper JU3. In this configuration, the error amplifier's output is inverted to provide the correct feedback polarity. The feedback regulation point is 0V. To modify the EV kit for a negative output voltage: 1) Cut the PC board trace to open jumpers JU1, JU4, and JU5.
2) Short jumpers JU2, JU6, and JU7 with a piece of wire. 3) Place the JU3 shunt across pins 2 and 3 (Table 2) 4) Install supplied components D2, D3, C4, and C7. Table 3 summarizes jumper JU1-JU7 settings.
Controlling the LCD Using POK and LCDON
POK can be used to turn off a positive LCD bias voltage when VBATT is too low. A resistor-divider (R1-R2) from V BATT to POK controls the open-drain output, LCDON, which pulls low when VPOK > 1V. LCDON drives an external PNP transistor, Q1, switching a positive VOUT to the LCD. Choose a PNP with low saturation voltage at the required load current. R6 limits the base current in Q1. R7 is used to turn off Q1 when LCDON is floating. R6 and R7 can be the same value. Refer to the Controlling the LCD Using POK and LCDON section in the MAX1620/MAX1621 data sheet for instructions on selecting resistors R1, R2, R6, and R7.
Evaluating the MAX1621
To evaluate the MAX1621, remove the MAX1620 IC and resistors R8, R9, and R10.
Table 2. Jumper JU3 Settings
SHUNT LOCATION 1 and 2 2 and 3 POL PIN Connected to VIN Connected to GND MAX1620 OUTPUT Positive output, VOUT = +17.8V Negative output, VOUT = -16.7V
Jumper Selection
Shutdown Mode The MAX1620 EV kit features a shutdown mode that reduces the MAX1620 quiescent current to 14A to preserve battery life. The two-pin header JU8 selects the shutdown mode. Table 1 lists the selectable jumper options. Positive Output Voltage This EV kit is shipped with the MAX1620's polarity pin (POL) tied to VIN for converting to a positive output voltage. A boost topology is used, and the feedback regulation point is 1.5V. Refer to the Output Adjustment section in the MAX1620/MAX1621 data sheet for instructions on selecting the feedback resistors.
Table 3. Jumper JU1- JU7 Settings
JUMPER JU1 JU2 JU3 JU4 JU5 JU6 JU7 POSITIVE OUT Short Open Short 1 and 2 Short Short Open Open NEGATIVE OUT Open Short Short 2 and 3 Open Open Short Short
2
_______________________________________________________________________________________
VBATT 1.8V TO 12V R11 10k PARTS FOR NEGATIVE OUTPUT D3 MBR0540T1 C4 1F D2 MBR0540T1 JU7 VOUT N1 MMFT3055VL 1 JU4 2 1 JU5 D1 MBR0540T1 Q1 CMPT2907 2 C7 22F 35V D4 REF R1 82k CMPSH-3 JU6 3 C2 0.1F POK LX DHI DLO PGND LCDON DOUT DOUT FB 9 R4 300k R5 2.2M 10 8 13 15 16 REF VDD 6 5 BATT 14 L1 100H
C1 22F 35V R2 100k
Figure 1. MAX1620 EV Kit Main Circuit Schematic
U1 MAX1620
11 R8* 100k 4 SHDN (SUS) UP (SCL) 2 (SUS) 1 DN (SDA) 12 GND POL 7 VIN JU3 1 3 2 (SDA) JU2 REF 1 JU1 2 R3 300k R9* 100k GND (SCL) R10* 100k C5 100pF VOUTSW C6 22F 35V R7 56k R6 56k
REF 1.5V
VIN 3V TO 5.5V
C3 0.1F
VIN
SHDN
JU8
UP
DN
GND
Evaluates: MAX1620/MAX1621
_______________________________________________________________________________________
* = REQUIRED FOR MAX1620 ONLY. ( ) ARE FOR MAX1621 ONLY.
MAX1620 Evaluation Kit
3
MAX1620 Evaluation Kit Evaluates: MAX1620/MAX1621
1.0"
Figure 2. MAX1620 EV Kit Component Placement Guide
1.0"
1.0"
Figure 3. MAX1620 EV Kit Component Placement Guide-- Component Side
Figure 4. MAX1620 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.
4 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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