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19-2502; Rev 0; 6/02
MAX1968 Evaluation Kit
General Description
The MAX1968 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 3.0V to 5.5V supply and provides a bipolar 3A (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 MAX1968 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(R) 95, 98, or 2000. Software, included with the EV kit, provides a quick and easy method to control the DAC. Note: Windows 2000 requires the installation of a driver. Refer to Win2000.pdf or Win2000.txt located on the diskette. o 3A Output Current o Operates from a Single Supply (3.0V to 5.5V) o High-Efficiency Switch-Mode Design o 500kHz or 1MHz Switching Frequency o Programmable Heating/Cooling Limit o TEC Current-Monitor Output o SPITM-Compatible Serial Interface o Easy-to-Use Menu-Driven Software o Includes Windows 95/98/2000-Compatible Software and Demo PC Board o Surface-Mount Construction o Fully Assembled and Tested
Features
Evaluates: MAX1968
Ordering Information
PART MAX1968EVKIT TEMP RANGE 0C to 70C PIN-PACKAGE 28 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 1F, 16V X5R ceramic capacitors (1206) Murata GRM319R71C105K Taiyo Yuden EMK316BJ105KF TDK C3216X7R1E105K 1F, 10V X5R ceramic capacitors (0805) Murata GRM21BR71A105K Taiyo Yuden LMK212BJ105MG TDK C2012X5R1A105K 10F, 6.3V X5R ceramic capacitors (1206) Murata GRM31CR60J106K Taiyo Yuden JMK316BJ106ML TDK C3216X5R0J106M 0.01F, 50V X7R ceramic capacitor (0603) Murata GRM188R71H103K Taiyo Yuden UMK107B103KZ TDK C1608X7R1H103K DESIGNATION C9 QTY 0 DESCRIPTION Not installed 0.1F, 16V X7R ceramic capacitors (0603) Murata GRM188R71C104K Taiyo Yuden EMK107BJ104KA TDK C1608X7R1C104K 0.022F, 50V X7R ceramic capacitor (1206) 180F, 6.3V, SP-capacitor Panasonic EEFUE0J181XR DB-25 male right-angle connector 3-pin headers Not installed 3.3H, 3.5A inductors Sumida CDRH6D38-3R3NC NPN bipolar transistors, SOT23 Central Semiconductor CMPT3904 Diodes Inc. MMBT3904 Fairchild MMBT3904 General Semiconductor MMBT3904
C1, C15
2
C10, C12, C13, C14, C16
5
C2-C6
5
C17 C18 J1 JU1, JU2, JU4 JU3 L1, L2
1 1 1 3 0 2
C7, C11
2
C8
1
Q1, Q2, Q3
3
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
MAX1968 Evaluation Kit Evaluates: MAX1968
Component List (continued)
DESIGNATION QTY DESCRIPTION 0.05 1%, 0.5W sense resistor (2010) Vishay Dale WSL2010 0.050 1.0% IRC LRC-LR2010-01-R050-F 49.9k 1% resistor (0603) 100k 1% resistors (0603) Not installed 510k 5% resistor (1206) 10k 5% resistors (0603) 100k 5% resistor (0603) 10k, temp coefficient = 25ppm/C 0.1% resistor (0805) DESIGNATION R15, R16, R17, R21 R18, R19, R20 R22 R23 SW1 U1 U2 U3 U4 None QTY 4 3 1 1 1 1 1 1 1 3 DESCRIPTION 1k 5% resistors (0603) 4.7k 5% resistors (0603) 10k potentiometer 240k 5% resistor (1206) Switch, momentary, normally open MAX1968EUI, 28-pin TSSOP-EP, driver for TEC module MAX4475ASA, 8-pin SO, op amp MAX4477ASA, 8-pin SO, dual op amp MAX5144EUB, 10-pin MAX, DAC Shunts
R1
1
R2 R3, R4, R5 R6-R9 R10 R11, R14 R12 R13
1 3 0 1 2 1 1
Component Suppliers
SUPPLIER Central Semiconductor Diodes Incorporated Fairchild General Semiconductor International Resistive Co. (IRC) Murata Panasonic Sumida Taiyo Yuden TDK Vishay Dale PHONE 631-435-1110 805-446-4800 888-522-5372 760-804-9258 361-992-7900 770-436-1300 714-373-7366 847-545-6700 800-348-2496 847-803-6100 402-564-3131 FAX 631-435-1824 805-381-3899 -- 760-804-9259 361-992-3377 770-436-3030 714-737-7323 847-545-6720 847-925-0899 847-390-4405 402-563-6296 WEBSITE www.centralsemi.com www.diodes.com www.fairchildsemi.com www.gensemi.com www.irctt.com www.murata.com www.panasonic.com www.sumida.com www.t-yuden.com www.component.tdk.com www.vishay.com
Note: Please indicate you are using the MAX1968 when contacting these manufacturers.
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MAX1968 Evaluation Kit
Quick Start
Required Equipment
Before beginning, the following equipment is required: * A DC power supply capable of supplying any voltage between 3V and 5.5V at 3A * A Peltier TEC module with a thermistor (10k at +25C) * A digital voltmeter (DVM) Procedure The MAX1968 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: 1) Place a shunt across pins 2 and 3 on JU1 to set the frequency to 500kHz. 2) Place a shunt across pins 2 and 3 on JU4 to select the potentiometer. 3) Place a shunt across pins 2 and 3 on JU2 to disable the MAX1968 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 MAX1968 MAXV, MAXIP (heating current), and MAXIN (cooling current) inputs. See Tables 1, 2, and 3 to select resistors or refer to the MAX1968 data sheet. 5) Connect the TEC module to OS1, OS2, THERM, and GND. Typical connections for most modules are: a) b) c) d) e) Module TEC- to OS1 Module TEC+ to OS2 Module thermistor to THERM Second module thermistor pin to GND Module case ground or shield to GND
Evaluates: MAX1968
Table 1. Maximum TEC Voltage
VMAXV (V) 1 0.65 VTEC(MAX) (V) 4V 2.6V R2 (k) 49.9 130 R3 (k) 100 100
Table 2. Maximum Positive TEC Current
ITECP(MAX) (A) 3.0 1.5 1.0 R6 (k) Short 100 100 R7 (k) Open 100 49.9
Table 3. Maximum Negative TEC Current
ITECN(MAX) (A) 3.0 1.5 1.0 R4 (k) Short 100 100 R5 (k) Open 100 49.9
voltage of approximately 0.75V. This represents +25C at the TEC module. 11) Enable the MAX1968 by moving the shunt on JU2 to the 1 and 2 position. 12) After enabling the MAX1968, verify that the THERM voltage converges toward the set-point voltage on R22 (set to 0.75V in step 9) after approximately 30s. If the TEC is connected backwards, the THERM voltage moves away from 0.75V toward either 0V or 1.5V. If this occurs, shut down the MAX1968 and reverse the TEC+ and TEC- connections 13) Once operation is verified, other temperatures may be set with R22, the DAC, or an external voltage applied to SET-POINT-IN; 1V is approximately +10C and 0.5V is approximately +40C. The slope is approximately -14mV/C.
Detailed Description
Voltage and Current-Limit Settings
The MAX1968 provides control of the maximum differential TEC voltage and the maximum positive and negative TEC current. The voltage on the MAXV pin of the MAX1968 sets the maximum differential TEC voltage. Use the following equations to set the voltage: Voltage on MAXV:
VMAXV (V) = REF x R3 R2 + R3
6) 7) 8) 9)
Be sure to check module specifications before making connections. Also, it is recommended that the thermistor be connected through shielded wire for lowest noise. Connect the DVM to SET-POINT-IN and GND. Connect a 3.3VDC or 5VDC power supply with sufficient power rating to VDD and GND. Turn on the power supply. Adjust R22 until the DVM reads 0.75V. This adjusts the set point for approximately +25C.
10) Move the DVM positive lead to THERM and verify a
V = 4 x VMAXV Maximum TEC Voltage: TEC(MAX) The components installed on the MAX1968 EV kit set
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MAX1968 Evaluation Kit Evaluates: MAX1968
VMAXV to 1V, for a maximum TEC voltage of 4V. See Table 1 and refer to the MAX1968 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) = REF x R6 + R7 Voltage on MAXIP: VMAXIN(V) = REF x R5 R4 + R5
Jumper JU1
Jumper JU1 sets the switching frequency for the MAX1968. Positions 1 and 2 set the frequency to 1MHz. Positions 2 and 3 set the frequency to 500kHz.
Jumper JU2
The MAX1968 can be placed in shutdown mode using jumper JU2. See Table 4 for jumper settings.
Jumper JU3
Jumper JU3 connects the current-control input (CTLI) of the MAX1968 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 JU3 and apply a DC voltage between 0 and 3V to the CTLI pad; 1.5V on CTLI sets a TEC current of approximately 0A. A voltage of 0V or 3V on CTLI produces -3A or +3A, respectively. The current changes proportionally with the voltage applied to CTLI. Note: The current does not reach 3A 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 MAX1968 data sheet for more information.
Voltage on MAXIN: Resistor values for R2 through R7 should be between 10k and 100k: Maximum Positive TEC Current:
VMAXIP 10 ITECP(MAX)(A) = + RSENSE
where RSENSE (R1) is 50m: Maximum Negative TEC Current: VMAXIN I TECN(MAX) (A) = - 10 RSENSE
The components installed on the MAX1968 EV kit limit the maximum positive current to +3A and the maximum negative current to -1.5A. See Tables 2 and 3, and refer to the MAX1968 data sheet for more information.
Jumper JU4
Jumper JU4, in positions 1 and 2, 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 2 and 3 connect potentiometer R22 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 +25C; 1V is approximately +10C and 0.5V is approximately +40C. The slope is approximately -14mV/C.
Table 4. Jumper Selection
JUMPER JUMPER POSITION 1 and 2 JU1 2 and 3* 1 and 2* 2 and 3 Cut PC Trace JU3 Closed* 1 and 2 JU4 2 and 3* Open FUNCTION MAX1968 switching frequency is 1MHz. MAX1968 switching frequency is 500kHz. SHDN = high. MAX1968 enabled. SHDN = low. MAX1968 disabled. Drive the CTLI pad directly with a DC voltage. Disconnects the thermal-loop circuit. Thermal control loop is closed. DAC or R22 generate temperature setpoint. DAC generates temperature setpoint. R22 generates temperature setpoint. Voltage applied to SET-POINT-IN generates temperature setpoint.
Switch SW1
Switch SW1 resets the DAC to 0.75V.
JU2
ITEC Current-Monitor Output
The ITEC output provides a voltage proportional to the actual TEC current. VITEC = REF when TEC current is zero. The actual TEC current is: V - 1.5V VTEC = ITEC 8 x R1 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 100pF.
*Default position 4 _______________________________________________________________________________________
MAX1968 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 2000. Note: Windows 2000 requires the installation of a driver; refer to Win2000.pdf or Win2000.txt located on the diskette. * A parallel printer port (this is a 25-pin socket on the back of the computer). * A standard 25-pin, straight-through, male-to-female cable (printer extension cable) to connect the computer's parallel port to the MAX1968 EV kit. 7) The MAX1968.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 95/98/2000 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 3.3VDC or 5VDC power supply with sufficient power rating to VDD and GND. 9) Turn on the power supply. 10) Start the MAX1968 program by opening its icon in the start menu. At program startup, the software forces the DAC to 0.75V, which corresponds to approximately +25C. 11) Connect the DVM to THERM and verify a voltage of approximately 0.75V. This represents +25C at the TEC module. 12) Enable the MAX1968 by moving the shunt on JU2 to the 1 and 2 position. 13) After enabling the MAX1968, verify that the THERM voltage converges toward the DAC voltage (0.75V) after approximately 30s. If the TEC is connected backwards, the THERM voltage moves away from 0.75V toward either 0V or 1.5V. If this occurs, shut down the MAX1968 and reverse the TEC+ and TEC- connections. 14) Once operation is verified, other temperatures may be set with the DAC. See the User Interface section.
Evaluates: MAX1968
Procedure 1) Place a shunt across pins 2 and 3 on JU1 to set the frequency to 500kHz. 2) Place a shunt across pins 1 and 2 on JU4 to select the DAC. 3) Place a shunt across pins 2 and 3 on JU2 to disable the MAX1968 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 MAX1968 MAXV, MAXIP (heating current), MAXIN (cooling current) inputs. See Tables 1, 2, and 3 to select resistors or refer to the MAX1968 data sheet. 5) Connect the TEC module to OS1, OS2, THERM, and GND. Typical connections for most modules are: a) Module TEC- to OS1 b) Module TEC+ to OS2 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 MAX1968 EV kit. Use a straight-through 25pin female-to-male cable. To avoid damaging the EV kit or your computer, do not use a 25-pin SCSI port or any other connector that is physically similar to the 25-pin parallel printer port.
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 (VDAC) to the reference voltage (REF). See the equation below: V Ratio = DAC REF where REF = 1.5V. The ratio must be a decimal number between 0 and 1. 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 1V, which corresponds to approximately +10C. A ratio of 0.33 sets the DAC output to 0.5V, or approximately +40C. The slope is approximately -14mV/C.
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MAX1968 Evaluation Kit Evaluates: MAX1968
General-Purpose SPI Utility
There are two methods for communicating with the MAX5144 DAC: through the user-interface panel or through the general-purpose SPI utility. This utility (Figure 3) 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 16-bit word should be broken into two 8-bit bytes. 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 MAX5144 is a write-only device and cannot be read.
1.5V REF
DAC SETPOINT-IN 1.5V REF CTLI
OS1 10k OS2 1.5V REF
TEC+ N P
TEC-
THERM MAX1968
10k
10k THERMISTOR THERMAL LINK
Figure 1. Thermal Loop Functional Diagram for the MAX1968 EV Kit
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MAX1968 Evaluation Kit Evaluates: MAX1968
Figure 2. Main Window for the MAX1968 EV Kit
Figure 3. SPI Utility Showing the Settings to Communicate with the MAX1968 EV Kit _______________________________________________________________________________________ 7
MAX1968 Evaluation Kit Evaluates: MAX1968
VDD VDD C18 180F 6.3V 1 C1 1F 2 VDD GND MAXIP 27 MAXV 28
R2 49.9k 1%
REF R3 100k 1% REF R7 OPEN REF R5 100k 1%
GND CTL1
R6 SHORT (PC TRACE)
3 CTL1 REF 4 VDD C2 1F 9 C3 1F 5
CTL1
REF MAXIN PVDD2 COMP U1 MAX1968 PVDD1 PGND1 PGND1 20 24 22 25 26
R4 100k 1%
PGND2 7 PGND2 LX2 8 LX2 10 LX2 VDD 11 PVDD2 1 2 3 JU1 12 FREQ 6
R8 OPEN C8 0.01F VDD C9 OPEN
L1 3.3H OS2 C5 1F
C4 1F L2 3.3H VDD C6 1F
ITEC OS2 (TEC+) C7 10F OS2 CS
13 14
ITEC OS2
LX1 23 21 LX1 19 LX1 18 PVDD1 SHDN 17
1 JU2 2 3 CS R1 0.05 1%
CS
16
OS1
15
OS1 (TEC-)
Figure 4. MAX1968 EV Kit Schematic
8
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MAX1968 Evaluation Kit Evaluates: MAX1968
J1-3 J1-11 J1-2 J1-4 J1-9 J1-18 J1-19 J1-20 J1-21 J1-22 J1-23 J1-24 J1-25 X_CS R18 4.7k 1 R15 1k 2 R19 4.7k X_SCLK Q1 1 R16 1k 2 R20 4.7k X_DIN Q2 1 R17 1k 2 Q3 3 4 DIN 3 3 SCLK CLR GND DIN INV RFB 7 8 GND 5 10 SW1 3 2 CS U4 SCLK MAX5144 R21 1k SET-POINT-IN SET-POINT-IN OUT X_DIN X_SCLK X_CS J1-10 DB-25 CONNECTOR J1-1 J1-5 J1-6 J1-7 J1-8 J1-12 J1-13 J1-14 J1-15 J1-16 J1-17 N.C. N.C. N.C. N.C. N.C. N.C. N.C. N.C. N.C. N.C. N.C. REF VDD C13 0.1F R12 100k REF VDD 1 REF 9 VDD 1 JU4 3 6 SET-POINT-IN 2 C16 0.1F VDD R22 10k 5 6 8 U3-B 4 C14 0.1F 7
MAX4477
CTL1
VDD
U3-B-OUT R9 SHORT (PC TRACE) 3 2 R10 510k C15 1F
JU3 OPEN
C10 0.1F 6
MAX4475
8 7 U2 4
REF R13 10k 0.1%
MAX4477
C11 10F C17 0.022F
R23 240k
R11 10k
3 2
THERM GND
1
U3-A
VDD CS
C12 0.1F
R14 10k
U3-B-OUT
VDD
VDD
Figure 5. MAX1968 EV Kit Schematic--Thermal Loop
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MAX1968 Evaluation Kit Evaluates: MAX1968
Figure 6. MAX1968 EV Kit Component Placement Guide-- Component Side
Figure 7. MAX1968 EV Kit Component Placement Guide-- Solder Side
Figure 8. MAX1968 EV Kit PC Board Layout (2oz Copper)-- Component Side
Figure 9. MAX1968 EV Kit PC Board Layout (2oz Copper)-- Ground Plane
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MAX1968 Evaluation Kit Evaluates: MAX1968
Figure 10. MAX1968 EV Kit PC Board Layout (2oz Copper)-- Power Plane
Figure 11. MAX1968 EV Kit PC Board Layout (2oz 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, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 11 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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