19-1214; Rev 1; 1/98 MAX1620 Evaluation Kit 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 (SMBus™) 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. Component List DESIGNATION QTY DESCRIPTION C1, C6 2 22µF, 35V tantalum capacitors AVX TPSE226M035R0300 or Sprague 593D226X0035E2T C2, C3 2 0.1µF ceramic capacitors C5 1 100pF ceramic capacitor D1 1 Schottky diode Motorola MBR0540T1 D4 1 Schottky diode Central Semiconductor CMPSH-3 L1 1 100µH inductor Sumida CD54-101 N1 1 Q1 R1 R2, R8, R9, R10 1 1 4 Features ♦ +1.8V to +12V Battery Input Voltage ♦ +12.5V to +23.5V Adjustable Output ♦ 20mA Output ♦ 32-Level Internal DAC ♦ 10µA Shutdown Current ♦ Surface-Mount Components ♦ Fully Assembled and Tested Ordering Information PART TEMP. RANGE BOARD TYPE MAX1620EVKIT 0°C to +70°C Surface Mount Note: To evaluate the MAX1621, request a free MAX1621EEE sample with the MAX1620 EV kit. Component Suppliers PHONE FAX AVX 803-946-0690 803-626-3123 Central Semiconductor 516-435-1110 516-435-1824 Coilcraft 847-639-6400 847-639-1469 Coiltronics 561-241-7876 561-241-9339 N-channel MOSFET Motorola MMFT3055VL Dale-Vishay 402-564-3131 402-563-6418 2N2907A transistor Central Semiconductor CMPT2907A Motorola 602-303-5454 602-994-6430 Sprague 603-224-1961 603-224-1430 82kΩ, 5% resistor Sumida 847-956-0666 847-956-0702 100kΩ, 5% resistors Vishay/Vitramon 203-268-6261 203-452-5670 R3, R4 2 300kΩ, 5% resistors R5 1 2.2MΩ, 5% resistor R6, R7 2 56kΩ, 5% resistors R11 1 10kΩ, 5% resistor U1 1 MAX1620EEE (QSOP-16) JU3 1 3-pin header None 1 Shunt (JU3) JU8 1 2-pin header None 1 MAX1620/MAX1621 PC board None 1 MAX1620/MAX1621 data sheet Additional components for negative output (included in 1 Shunt the EV kit) but not installed: C4 1 1µF ceramic capacitor C7 1 22µF, 35V tantalum capacitor AVX TPSE226M035R0300 or Sprague 593D226X0035E2T D2, D3 2 Schottky diodes Motorola MBR0540T1 SMBus is a trademark of Intel Corp. SUPPLIER* * 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. ________________________________________________________________ Maxim Integrated Products 1 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. Evaluates: MAX1620/MAX1621 General Description Evaluates: MAX1620/MAX1621 MAX1620 Evaluation Kit _______________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 SHDN PIN On Connected to GND Shutdown mode, VOUT = VBATT, VOUTSW = float Off Connected to VIN MAX1620 enabled, VOUT = +17.8V Output Voltage Control MAX1620 OUTPUT 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. Controlling the LCD Using POK and LCDON 3) Place the JU3 shunt across pins 2 and 3 (Table 2) 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. 4) Install supplied components D2, D3, C4, and C7. Table 3 summarizes jumper JU1–JU7 settings. Jumper Selection Shutdown Mode The MAX1620 EV kit features a shutdown mode that reduces the MAX1620 quiescent current to 14µA 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. 2 2) Short jumpers JU2, JU6, and JU7 with a piece of wire. Evaluating the MAX1621 To evaluate the MAX1621, remove the MAX1620 IC and resistors R8, R9, and R10. Table 2. Jumper JU3 Settings SHUNT LOCATION POL PIN 1 and 2 Connected to VIN Positive output, VOUT = +17.8V 2 and 3 Connected to GND Negative output, VOUT = -16.7V MAX1620 OUTPUT Table 3. Jumper JU1– JU7 Settings JUMPER POSITIVE OUT NEGATIVE OUT JU1 Short Open JU2 Open Short JU3 Short 1 and 2 Short 2 and 3 JU4 Short Open JU5 Short Open JU6 Open Short JU7 Open Short _______________________________________________________________________________________ DN UP SHDN VIN 3V TO 5.5V REF 1.5V R8* 100k (SDA) R10* 100k (SCL) R9* 100k (SUS) VIN * = REQUIRED FOR MAX1620 ONLY. ( ) ARE FOR MAX1621 ONLY. GND JU8 C3 0.1µF C2 0.1µF R2 100k C1 22µF 35V GND 12 3 U1 MAX1620 UP (SCL) VIN GND D4 JU3 1 REF 2 7 POL LX 3 9 10 8 13 15 JU2 FB DOUT LCDON PGND DLO 16 14 REF DHI CMPSH-3 BATT SHDN (SUS) VDD REF POK 1 DN (SDA) 2 4 11 6 5 R1 82k R11 10k 1 R3 300k JU1 R4 300k 2 JU4 C4 1µF C5 100pF R5 2.2M JU6 N1 MMFT3055VL 1 L1 100µH DOUT 2 D1 MBR0540T1 JU7 D2 MBR0540T1 D3 MBR0540T1 1 R6 56k JU5 C7 22µF 35V PARTS FOR NEGATIVE OUTPUT 2 C6 22µF 35V R7 56k Q1 CMPT2907 VOUTSW VOUT Evaluates: MAX1620/MAX1621 VBATT 1.8V TO 12V MAX1620 Evaluation Kit Figure 1. MAX1620 EV Kit Main Circuit Schematic _______________________________________________________________________________________ 3 Evaluates: MAX1620/MAX1621 MAX1620 Evaluation Kit 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 © 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.