C10, C12, C13, C14, C16. Maxim Integrated Products 1

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1 9-50; Rev 0; 6/0 MAX968 Evaluation Kit General Description The MAX968 evaluation kit (EV kit) is a fully assembled and tested PC board that implements a switch-mode driver for a Peltier thermoelectric cooler (TEC) module. It operates from a single.0v to 5.5V supply and provides a bipolar ±A (max) output to the module. A potentiometer, DAC, or external source generates a DC temperature set-point voltage. Thermal feedback from the TEC module is compared to the set-point voltage to generate the TEC current-control signal. The MAX968 accurately regulates the TEC current based on this signal. When using the DAC, the EV kit connects to the parallel port of a computer running Windows 95, 98, or 000. Software, included with the EV kit, provides a quick and easy method to control the DAC. Note: Windows 000 requires the installation of a driver. Refer to Win000.pdf or Win000.txt located on the diskette. DESIGNATION QTY DESCRIPTION C, C5 C C6 5 C7, C C8 µf, 6V X5R ceramic capacitors (06) Murata GRM9R7C05K Taiyo Yuden EMK6BJ05KF TDK C6X7RE05K µf, 0V X5R ceramic capacitors (0805) Murata GRMBR7A05K Taiyo Yuden LMKBJ05MG TDK C0X5RA05K 0µF, 6.V X5R ceramic capacitors (06) Murata GRMCR60J06K Taiyo Yuden JMK6BJ06ML TDK C6X5R0J06M 0.0µF, 50V X7R ceramic capacitor (060) Murata GRM88R7H0K Taiyo Yuden UMK07B0KZ TDK C608X7RH0K Features ±A Output Current Operates from a Single Supply (.0V to 5.5V) High-Efficiency Switch-Mode Design 500kHz or MHz Switching Frequency Programmable Heating/Cooling Limit TEC Current-Monitor Output SPI -Compatible Serial Interface Easy-to-Use Menu-Driven Software Includes Windows 95/98/000-Compatible Software and Demo PC Board Surface-Mount Construction Fully Assembled and Tested Ordering Information PART TEMP RANGE PIN-PACKAGE MAX968EVKIT 0 C to 70 C 8 TSSOP-EP* *EP = Exposed pad. Windows is a registered trademark of Microsoft Corp. SPI is a trademark of Motorola, Inc. Component List DESIGNATION QTY DESCRIPTION C9 0 Not installed C0, C, C, C4, C6 5 C7 0.µF, 6V X7R ceramic capacitors (060) Murata GRM88R7C04K Taiyo Yuden EMK07BJ04KA TDK C608X7RC04K 0.0µF, 50V X7R ceramic capacitor (06) 80µF, 6.V, SP-capacitor C8 Panasonic EEFUE0J8XR J DB-5 male right-angle connector JU, JU, JU4 -pin headers JU 0 Not installed L, L Q, Q, Q.µH,.5A inductors Sumida CDRH6D8-RNC NPN bipolar transistors, SOT Central Semiconductor CMPT904 Diodes Inc. MMBT904 Fairchild MMBT904 General Semiconductor MMBT904 Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at , or visit Maxim s website at

2 MAX968 Evaluation Kit DESIGNATION QTY DESCRIPTION R 0.05Ω ±%, 0.5W sense resistor (00) Vishay Dale WSL % IRC LRC-LR00-0-R050-F R 49.9kΩ ±% resistor (060) R, R4, R5 00kΩ ±% resistors (060) R6 R9 0 Not installed R0 50kΩ ±5% resistor (06) R, R4 0kΩ ±5% resistors (060) R 00kΩ ±5% resistor (060) R 0kΩ, temp coefficient = 5ppm/ C ±0.% resistor (0805) Component List (continued) DESIGNATION QTY DESCRIPTION R5, R6, R7, R 4 kω ±5% resistors (060) R8, R9, R0 4.7kΩ ±5% resistors (060) R 0kΩ potentiometer R 40kΩ ±5% resistor (06) SW Switch, momentary, normally open MAX968EUI, 8-pin TSSOP-EP, U driver for TEC module U MAX4475ASA, 8-pin SO, op amp MAX4477ASA, 8-pin SO, dual op U amp U4 MAX544EUB, 0-pin µmax, DAC None Shunts Component Suppliers SUPPLIER PHONE FAX WEBSITE Central Semiconductor Diodes Incorporated Fairchild General Semiconductor International Resistive Co. (IRC) Murata Panasonic Sumida Taiyo Yuden TDK Vishay Dale Note: Please indicate you are using the MAX968 when contacting these manufacturers.

3 MAX968 Evaluation Kit Quick Start Required Equipment Before beginning, the following equipment is required: A DC power supply capable of supplying any voltage between V and 5.5V at A A Peltier TEC module with a thermistor (0kΩ at +5 C) A digital voltmeter (DVM) Procedure The MAX968 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: ) Place a shunt across pins and on JU to set the frequency to 500kHz. ) Place a shunt across pins and on JU4 to select the potentiometer. ) Place a shunt across pins and on JU to disable the MAX968 output. 4) Obtain TEC module specifications for absolute maximum TEC voltage, absolute maximum cooling current, and absolute maximum heating current. Set these (or lower) limits at the MAX968 MAXV, MAXIP (heating current), and MAXIN (cooling current) inputs. See Tables,, and to select resistors or refer to the MAX968 data sheet. 5) Connect the TEC module to OS, OS, THERM, and GND. Typical connections for most modules are: a) Module TEC- to OS b) Module TEC+ to OS c) Module thermistor to THERM d) Second module thermistor pin to GND e) Module case ground or shield to GND Be sure to check module specifications before making connections. Also, it is recommended that the thermistor be connected through shielded wire for lowest noise. 6) Connect the DVM to SET-POINT-IN and GND. 7) Connect a.vdc or 5VDC power supply with sufficient power rating to and GND. 8) Turn on the power supply. 9) Adjust R until the DVM reads 0.75V. This adjusts the set point for approximately +5 C. 0) Move the DVM positive lead to THERM and verify a Table. Maximum TEC Voltage V MAXV (V) V TEC(MAX) (V) R (kω) R (kω) 4V V 0 00 Table. Maximum Positive TEC Current I TECP(MAX) (A) R6 (kω) R7 (kω).0 Short Open Table. Maximum Negative TEC Current I TECN(MAX) (A) R4 (kω) R5 (kω).0 Short Open voltage of approximately 0.75V. This represents +5 C at the TEC module. ) Enable the MAX968 by moving the shunt on JU to the and position. ) After enabling the MAX968, verify that the THERM voltage converges toward the set-point voltage on R (set to 0.75V in step 9) after approximately 0s. If the TEC is connected backwards, the THERM voltage moves away from 0.75V toward either 0V or.5v. If this occurs, shut down the MAX968 and reverse the TEC+ and TEC- connections ) Once operation is verified, other temperatures may be set with R, the DAC, or an external voltage applied to SET-POINT-IN; V is approximately +0 C and 0.5V is approximately +40 C. The slope is approximately -4mV/ C. Detailed Description Voltage and Current-Limit Settings The MAX968 provides control of the maximum differential TEC voltage and the maximum positive and negative TEC current. The voltage on the MAXV pin of the MAX968 sets the maximum differential TEC voltage. Use the following equations to set the voltage: R VMAXV Voltage on MAXV: ( V) = R + R V V Maximum TEC Voltage: TEC(MAX) = 4 MAXV The components installed on the MAX968 EV kit set

4 MAX968 Evaluation Kit V MAXV to V, for a maximum TEC voltage of 4V. See Table and refer to the MAX968 data sheet for more information. The voltages on the MAXIP and MAXIN pins set the maximum positive (heating) and negative (cooling) current through the TEC. Use the following equations to set the currents: R7 VMAXIP( V) = Voltage on MAXIP: R6 + R7 R5 VMAXIN( V) = Voltage on MAXIN: R4 + R5 Resistor values for R through R7 should be between 0kΩ and 00kΩ: Maximum Positive TEC Current: VMAXIP I 0 TECP(MAX) ( A ) = + R where R SENSE (R) is 50mΩ: Maximum Negative TEC Current: ITECN(MAX) ( A ) SENSE VMAXIN = 0 RSENSE The components installed on the MAX968 EV kit limit the maximum positive current to +A and the maximum negative current to -.5A. See Tables and, and refer to the MAX968 data sheet for more information. Table 4. Jumper Selection JUMPER JU JU JU JU4 *Default position JUMPER POSITION FUNCTION and M AX 968 sw i tchi ng fr eq uency i s M H z. and * MAX968 switching frequency is 500kHz. and * SHDN = high. MAX968 enabled. and SHDN = low. MAX968 disabled. Cut PC Trace Drive the CTLI pad directly with a DC voltage. Disconnects the thermal-loop circuit. Closed* Thermal control loop is closed. DAC or R generate temperature setpoint. and DAC generates temperature setpoint. and * R generates temperature setpoint. Open Voltage applied to SET-POINT-IN generates temperature setpoint. Jumper JU Jumper JU sets the switching frequency for the MAX968. Positions and set the frequency to MHz. Positions and set the frequency to 500kHz. Jumper JU The MAX968 can be placed in shutdown mode using jumper JU. See Table 4 for jumper settings. Jumper JU Jumper JU connects the current-control input (CTLI) of the MAX968 to the thermal loop circuit. The thermal loop circuit compares thermistor feedback from the TEC module to the set-point voltage to generate the CTLI signal. To drive CTLI directly, cut the trace shorting JU and apply a DC voltage between 0 and V to the CTLI pad;.5v on CTLI sets a TEC current of approximately 0A. A voltage of 0V or V on CTLI produces -A or +A, respectively. The current changes proportionally with the voltage applied to CTLI. Note: The current does not reach ±A if the maximum positive and negative current limits are set to lower values. See the Voltage and Current-Limit Settings section and refer to the MAX968 data sheet for more information. Jumper JU4 Jumper JU4, in positions and, connects the DAC to the thermal loop circuit. Connect the EV kit to the parallel port of a computer and use the EV kit software to control the DAC. Positions and connect potentiometer R to the thermal loop circuit. To use an external voltage to control the thermal loop, remove the shunt from JU4 and apply the voltage to the SET-POINT-IN pad. A voltage of 0.75V corresponds to approximately +5 C; V is approximately +0 C and 0.5V is approximately +40 C. The slope is approximately -4mV/ C. Switch SW Switch SW resets the DAC to 0.75V. ITEC Current-Monitor Output The ITEC output provides a voltage proportional to the actual TEC current. V ITEC = when TEC current is zero. The actual TEC current is: V -.5V VTEC = ITEC 8 R Use ITEC to monitor the cooling or heating current through the TEC module. Positive values of ITEC indicate heating for typically connected modules. The maximum capacitance that ITEC can drive is 00pF. 4

5 MAX968 Evaluation Kit Using a Computer Required Equipment In addition to the equipment listed under the Quick Start section, the following equipment is necessary: A computer running Windows 95, 98, or 000. Note: Windows 000 requires the installation of a driver; refer to Win000.pdf or Win000.txt located on the diskette. A parallel printer port (this is a 5-pin socket on the back of the computer). A standard 5-pin, straight-through, male-to-female cable (printer extension cable) to connect the computer s parallel port to the MAX968 EV kit. Procedure ) Place a shunt across pins and on JU to set the frequency to 500kHz. ) Place a shunt across pins and on JU4 to select the DAC. ) Place a shunt across pins and on JU to disable the MAX968 output. 4) Obtain TEC module specifications for absolute maximum TEC voltage, absolute maximum cooling current, and absolute maximum heating current. Set these (or lower) limits at the MAX968 MAXV, MAXIP (heating current), MAXIN (cooling current) inputs. See Tables,, and to select resistors or refer to the MAX968 data sheet. 5) Connect the TEC module to OS, OS, THERM, and GND. Typical connections for most modules are: a) Module TEC- to OS b) Module TEC+ to OS c) Module thermistor to THERM d) Second module thermistor pin to GND e) Module case ground or shield to GND Be sure to check module specifications before making connections. Also, it is recommended that the thermistor be connected through shielded wire for lowest noise. 6) Connect a cable from the computer s parallel port to the MAX968 EV kit. Use a straight-through 5- pin female-to-male cable. To avoid damaging the EV kit or your computer, do not use a 5-pin SCSI port or any other connector that is physically similar to the 5-pin parallel printer port. 7) The MAX968.EXE software program can be run from the floppy or hard drive. Use the Windows program manager to run the program. If desired, the INSTALL.EXE program may be used to copy the files and create icons for them in the Windows 95/98/000 start menu. An uninstall program is included with the software. Click on the UNINSTALL icon to remove the EV kit software from the hard drive. 8) Connect a.vdc or 5VDC power supply with sufficient power rating to and GND. 9) Turn on the power supply. 0) Start the MAX968 program by opening its icon in the start menu. At program startup, the software forces the DAC to 0.75V, which corresponds to approximately +5 C. ) Connect the DVM to THERM and verify a voltage of approximately 0.75V. This represents +5 C at the TEC module. ) Enable the MAX968 by moving the shunt on JU to the and position. ) After enabling the MAX968, verify that the THERM voltage converges toward the DAC voltage (0.75V) after approximately 0s. If the TEC is connected backwards, the THERM voltage moves away from 0.75V toward either 0V or.5v. If this occurs, shut down the MAX968 and reverse the TEC+ and TEC- connections. 4) Once operation is verified, other temperatures may be set with the DAC. See the User Interface section. User Interface The user interface is easy to operate. Use either the mouse or the Tab key to navigate. To program the DAC, enter the ratio of the desired DAC output voltage (V DAC ) to the reference voltage (). See the equation below: V Ratio = DAC where =.5V. The ratio must be a decimal number between 0 and. Press Enter or click on the Update button to send the data to the DAC. A ratio of 0.67 sets the DAC output to V, which corresponds to approximately +0 C. A ratio of 0. sets the DAC output to 0.5V, or approximately +40 C. The slope is approximately -4mV/ C. 5

6 MAX968 Evaluation Kit General-Purpose SPI Utility There are two methods for communicating with the MAX544 DAC: through the user-interface panel or through the general-purpose SPI utility. This utility (Figure ) configures SPI parameters such as clock polarity (CPOL), clock phase (CPHA), and chip-select (CS) polarity. The fields where pin numbers are required apply to the pins of the parallel port connector. The utility handles the data only in byte (8-bit) format. Data longer than a byte must be handled as multiple bytes. For example, a 6-bit word should be broken into two 8-bit bytes..5v To write data to the slave device, enter the data into the field labeled Data Bytes to be Written. Each data byte should be hexadecimal, prefixed by 0x, and separated with a comma. Press the Send Now button to write the data to the slave. To read data from the slave device, the field labeled Data Bytes to be Written must contain hexadecimal values. Include the same number of bytes as to be read from the slave. Note: The MAX544 is a write-only device and cannot be read. DAC TEC- SET- POINT-IN.5V CTLI 0kΩ OS OS TEC+ N P.5V THERM MAX968 0kΩ 0kΩ THERMISTOR THERMAL LINK Figure. Thermal Loop Functional Diagram for the MAX968 EV Kit 6

7 MAX968 Evaluation Kit Figure. Main Window for the MAX968 EV Kit Figure. SPI Utility Showing the Settings to Communicate with the MAX968 EV Kit 7

8 MAX968 Evaluation Kit 8 U MAX968 R 49.9kΩ % R 0.05Ω % R 00kΩ % SHDN OS ITEC COMP P PGND PGND P CS OS MAXV MAXIP MAXIN LX LX LX 8 C µf GND CTL CTL JU OS (TEC+) OS (TEC-) P PGND PGND LX LX LX P FREQ ITEC OS V DD GND CTL C µf C8 0.0µF C9 OPEN C µf C7 0µF C5 µf L.µH L.µH C4 µf C6 µf CS OS CS R6 SHORT (PC TRACE) R7 OPEN 7 R4 00kΩ % R5 00kΩ % 6 R8 OPEN JU C8 80µF 6.V Figure 4. MAX968 EV Kit Schematic

9 MAX968 Evaluation Kit 9 U4 MAX544 GND INV RFB OUT X_CS CLR 4 9 V DD SW GND SET-POINT-IN CS R8 4.7kΩ Q CS SCLK C 0.µF C6 0.µF C 0.µF C7 0.0µF C 0µF C5 µf C0 0.µF R5 kω DIN U-B-OUT R9 SHORT (PC TRACE) R 00kΩ X_SCLK SCLK R9 4.7kΩ Q R6 kω X_DIN DIN R0 4.7kΩ Q R7 kω R 0kΩ R4 0kΩ R 0kΩ R0 50kΩ R 40kΩ R 0kΩ 0.% R kω SET-POINT-IN SET-POINT-IN GND THERM JU4 JU OPEN U-B-OUT U-B CTL U U-A DB-5 CONNECTOR J-5 J-4 J- J- J- J-0 J-9 J-8 J-9 J-4 J- J- J- J-7 J-6 J-5 J-4 J- J- J-8 J-7 J-6 J-5 J- J-0 X_CS X_SCLK X_DIN MAX4477 MAX4475 MAX4477 C4 0.µF Figure 5. MAX968 EV Kit Schematic Thermal Loop

10 MAX968 Evaluation Kit Figure 6. MAX968 EV Kit Component Placement Guide Component Side Figure 7. MAX968 EV Kit Component Placement Guide Solder Side Figure 8. MAX968 EV Kit PC Board Layout (oz Copper) Component Side Figure 9. MAX968 EV Kit PC Board Layout (oz Copper) Ground Plane 0

11 MAX968 Evaluation Kit Figure 0. MAX968 EV Kit PC Board Layout (oz Copper) Power Plane Figure. MAX968 EV Kit PC Board Layout (oz Copper) 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. Maxim Integrated Products, 0 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.