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19-2612; Rev 0A; 12/02
MAX1978 Evaluation Kit
General Description
The MAX1978 evaluation kit (EV kit) is a fully assembled and tested PC board that implements a complete switch-mode temperature control system for a Peltier thermo-electric cooler (TEC) module. It operates from a single 3V to 5.5V supply and provides a bipolar 2.2A (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 MAX1978 controls TEC current to accurately regulate temperature. When using the DAC, the EV kit connects to the parallel port of a computer running Windows(R) 95, 98, or 2000. o Circuit Footprint Less than 0.93in2 o Circuit Height Less than 3mm o Operates from a Single Supply (3V to 5.5V) o 2.2A Output Current o o o o High-Efficiency Switch-Mode Design Programmable Heating/Cooling Current Limit TEC Current Monitor Output Overtemperature, Undertemperature, and Analog Temperature Monitor
Features
Evaluates: MAX1978
o 500kHz or 1MHz Switching Frequency 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
Ordering Information
PART TEMP RANGE 0C to +70C IC PACKAGE 48 Thin QFN (7mm 7mm) MAX1978EVKIT
SPI is a trademark of Motorola, Inc. Windows is a registered trademark of Microsoft Corp.
Component List
DESIGNATION QTY DESCRIPTION 4.7F, 6.3V X5R, ceramic capacitor (0805) Murata GRM21BR60J475M Taiyo Yuden JMK212BJ475MG TDK C2012X5R0J475M 1F, 6.3V X5R ceramic capacitors (0603) Murata GRM188R60J105M Taiyo Yuden JMK107BJ105MA TDK C1608X5R1A105K 10F, 6.3V X5R ceramic capacitors (0805) Murata GRM21BR60J106K Taiyo Yuden JMK212BJ106MG TDK C2012X5R0J106M 0.01F, 16V X7R ceramic capacitor (0402) Murata GRP155R71C103K Taiyo Yuden EMK105BJ103KV TDK C1005X7R1E103K DESIGNATION C5 QTY 0 DESCRIPTION Not installed (0402) 0.47F, 6.3V X7R ceramic capacitor (0603) Murata GRM188R60J474K Taiyo Yuden LMK107BJ474KA TDK C1608X5R1A474K 0.047F, 10V X7R ceramic capacitor (0402) Murata GRP155R71A473K Taiyo Yuden LMK105BJ473KV TDK C1005X7R1C473K Not installed (0603) 22F, 6.3V X5R ceramic capacitor (1210) Murata GRM32DR60J226K Taiyo Yuden JMK325BJ226MM TDK C3225X5R0J226M
C1
1
C8
1
C2, C7, C12, C17
4
C10
1
C3, C6, C9, C11
4
C16, C21
0
C19
1
C4
1
Component List continued on next page.
________________________________________________________________ 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.
MAX1978 Evaluation Kit Evaluates: MAX1978
Component List (continued)
DESIGNATION C20 JU1, JU3, JU4 JU2 L1, L2 R1 R2 R3 R4-R8 R9 R10 R11 R12 R13 R14 R15 R16 R25, R26 QTY 0 3 1 2 1 1 1 0 1 1 1 1 1 1 1 1 2 DESCRIPTION Not installed (1210) 3-pin headers 2-pin header 3H, 2.4A inductors Sumida CDRH5D28-3R0NC 0.068 1%, 0.5W sense resistor (1206) IRC LRC-LR1206-01-R068-F 49.9k 1% resistor (0402) 100k 1% resistor (0402) Not installed (0402) 80.6k 1% resistor (0603) 69.8k 1% resistor (0603) 105k 1% resistor (0603) 20k 1% resistor (0603) 10k temp coefficient = 25ppm/C, 0.1% resistor (0805) 1M 5% resistor (0402) 20k 5% resistor (0402) 100k 5% resistor (0402) 100k 5% resistors (0603) Q1, Q2, Q3 3 DESIGNATION SW1 U1 None QTY 1 1 4 DESCRIPTION Switch, momentary, normally open MAX1978ETM 48-pin thin QFN-EP* Shunts
DAC AND INTERFACE COMPONENTS. REQUIRED ONLY FOR EVALUATION. 0.1F, 16V X7R ceramic capacitors (0603) C13, C14, C15 3 Murata GRM188R71C104K Taiyo Yuden EMK107BJ104KA TDK C1608X7R1C104K C18 0 Not installed (0603) J1 1 DB25 male right-angle connector NPN bipolar transistors, SOT23 Central Semiconductor CMPT3904 Diodes Inc. MMBT3904 Fairchild MMBT3904 General Semiconductor MMBT3904 1k 5% resistors (0603) 4.7k 5% resistors (0603) 20k potentiometer (multiturn) MAX5144EUB 10-pin MAX
R17, R18, R19, R23 R20, R21, R22 R24 U2
4 3 1 1
*EP = Exposed pad.
Component Suppliers
SUPPLIER Central Semiconductor Diodes Inc. Fairchild General Semiconductor International Rectifier Co. (IRC) Murata Sumida Taiyo Yuden TDK PHONE 631-435-1110 805-446-4800 888-522-5372 760-804-9258 361-992-7900 770-436-1300 847-545-6700 800-348-2496 847-803-6100 FAX 631-435-1824 805-381-3899 -- 760-804-9259 361-992-3377 770-436-3030 847-545-6720 847-925-0899 847-390-4405 WEBSITE www.centralsemi.com www.diodes.com www.fairchildsemi.com www.gensemi.com www.irctt.com www.murata.com www.sumida.com www.t-yuden.com www.component.tdk.com
Note: Please indicate you are using the MAX1978 when contacting these manufacturers.
Quick Start
Required Equipment
The following equipment is required before beginning: * One DC power supply capable of supplying any voltage between 3V and 5.5V at 3A
* One Peltier TEC module with a thermistor (NTC 10k at +25C) * One digital voltmeter (DVM)
2
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MAX1978 Evaluation Kit
Procedure
The MAX1978 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 2-3 on JU1 to set the frequency to 500kHz. 2) Place a shunt across JU2 to connect the thermal loop to CTLI. 3) Place a shunt across pins 2-3 on JU4 to select the potentiometer. 4) Place a shunt across pins 2-3 on JU3 to disable the MAX1978 output. 5) 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 MAX1978's MAXV, MAXIP (heating current), MAXIN (cooling current) inputs. See Tables 1, 2, and 3 to select resistors, or refer to the MAX1978 data sheet. 6) Connect the TEC module to OS1, OS2, THERM, and GND. Typical connections for most modules: * 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 Check module specifications before making connections. For lowest noise, connect the thermistor through shielded wire. 7) Connect the DVM to SET_POINT and GND. 8) Connect a 3.3V DC or 5V DC power supply with sufficient power rating to VDD and GND. 9) Turn on the power supply. Note: The MAX1978 output is not enabled yet. 10) Adjust R24 until the DVM reads 0.75V. This adjusts the set point for approximately +25C. 11) Move the DVM positive lead to THERM and verify a voltage of approximately 0.75V. This corresponds to an ambient temperature of +25C at the TEC module. 12) Enable the MAX1978 by moving the shunt on JU3 to the 1-2 position. 13) After enabling the MAX1978, verify that the THERM voltage converges toward the set-point voltage on R24 (set to 0.75V in Step 9) after approximately 30s. If the TEC is connected backward, the THERM voltage moves away from 0.75V toward either 0V or 1.5V. If this occurs, shut down the MAX1978 and reverse TEC+ and TEC- connections. 14) Once proper operation is verified, other temperatures can be set with R24, the DAC, or an external voltage applied to SET_POINT. (1V is approximately +10C; 0.5V is approximately +40C. The slope is approximately -14mV/C for a typical NTC.)
Evaluates: MAX1978
Detailed Description
Voltage and Current-Limit Settings
The MAX1978 provides control of the maximum differential TEC voltage and the maximum positive and negative TEC currents. The voltage on the MAXV pin of the MAX1978 sets the maximum differential TEC voltage. Use the following equations to set the voltage: Voltage on MAXV : VMAXV (V) = REF x R3 R2 + R 3
Maximum TEC voltage: VTEC(MAX) = 4 VMAXV The components installed on the MAX1978 EV kit set VMAXV to 1V, for a maximum TEC voltage of 4V. See Table 1 and refer to the MAX1978 data sheet for more information.
Table 1. Maximum TEC Voltage
VTEC(MAX) (V) 4 2.6 R2 (k) 49.9 130 R3 (k) 100 100
The voltages on the MAXIP and MAXIN pins set the maximum positive (heating) and negative (cooling) currents through the TEC. Use the following equations to set the currents: R7 Voltage on MAXIP : VMAXIP (V) = REF x R6 + R7 Voltage on MAXIN: VMAXIN (V) = REF x R5 R4 + R5
Resistor values for R2 through R7 should be between 10k and 100k. Maximum positive TEC current: I TECP(MAX) (A) = + where RSENSE (R1) is 68m. VMAXIP 10 x RSENSE
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3
MAX1978 Evaluation Kit Evaluates: MAX1978
Maximum negative TEC current: VMAXIN I TECN(MAX) (A) = - 10 x RSENSE The components installed on the MAX1978 EV kit set the maximum positive current to +2.2A and the maximum negative current to -2.2A. See Tables 2 and 3, and refer to the MAX1978 data sheet for more information. respectively. The current changes proportionally with the voltage applied to CTLI. Note: The current does not reach 2.2A 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 MAX1978 data sheet for more information.
Table 2. Maximum Positive TEC Current
ITECP(MAX) (A) 2.2 1.1 0.7 R6 (k) Short 100 100 R7 (k) Open 100 49.9
Jumper JU3
The MAX1978 can be placed in shutdown mode using jumper JU3. See Table 4 for jumper settings.
Jumper JU4
Jumper JU4, position 1-2, 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. Position 2-3 connects potentiometer R24 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 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 for a typical NTC.
Table 3. Maximum Negative TEC Current
ITECN(MAX) (A) 2.2 1.1 0.7 R4 (k) Short 100 100 R5 (k) Open 100 49.9
Jumper JU1
Jumper JU1 sets the switching frequency for the MAX1978. Position 1-2 sets the frequency to 1MHz. Position 2-3 sets it to 500kHz. Switch SW1 resets the DAC to 0.75V.
Switch SW1 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: I TEC = VITEC - 1.5V 8 x R1
Jumper JU2
Jumper JU2 connects the current-control input (CTLI) of the MAX1978 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, remove the shunt on JU2 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 -2.2A or +2.2A,
Use ITEC to monitor the cooling or heating current through the TEC module. Positive values of I TEC indicate heating for typically connected modules. The maximum capacitance that ITEC can drive is 100pF.
Table 4. Jumper Selection
JUMPER JU1 JU2 JU3 JUMPER POSITION 1-2 2-3* Open Closed* 1-2 2-3* 1-2 JU4 2-3* Open MAX1978 switching frequency is 1MHz. MAX1978 switching frequency is 500kHz. Drive the CTLI pad directly with a DC voltage. Disconnects the thermal-loop circuit. Thermal-control loop is closed. DAC or R24 generates temperature set point. SHDN = high, MAX1978 enabled. SHDN = low, MAX1978 disabled. DAC generates temperature set point. Potentiometer R24 generates temperature set point. Voltage applied to SET_POINT generates temperature set point. FUNCTION
*Default position 4 _______________________________________________________________________________________
MAX1978 Evaluation Kit
Controlling DAC Through Parallel Port
Required Equipment
In addition to the equipment listed under the Quick Start section, the the following equipment is required: * 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 (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 MAX1978 EV kit port or any other connector that is physically similar to the 25-pin parallel printer port. 8) The MAX1978.EXE software program can be run from the floppy or hard drive. Use the Windows program manager to run the program. If desired, you can use the INSTALL.EXE program 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. 9) Connect a 3.3V DC or 5.0V DC power supply with sufficient power rating to VDD and GND. 10) Turn on the power supply. 11) Start the MAX1978 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. 12) Connect the DVM to THERM and verify a voltage of approximately 0.75V. This represents +25C at the TEC module. 13) Enable the MAX1978 by moving the shunt on JU3 to the 1-2 position. 14) After enabling the MAX1978, verify that the THERM voltage converges toward the DAC voltage (0.75V) after approximately 30s. If the TEC is connected backward, the THERM voltage moves away from 0.75V toward either 0V or 1.5V. If this occurs, shut down the MAX1978 and reverse TEC+ and TECconnections. 15) Once proper operation is verified, other temperatures can be set with the DAC (see the Software User Interface section).
Evaluates: MAX1978
Procedure
1) Place a shunt across pins 2-3 on JU1 to set the frequency to 500kHz. 2) Place a shunt across JU2 to connect the thermal loop to CTLI. 3) Place a shunt across pins 1-2 on JU4 to select the DAC. 4) Place a shunt across pins 2-3 on JU3 to disable the MAX1978 output. 5) 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 MAX1978's MAXV, MAXIP (heating current), MAXIN (cooling current) inputs. See Tables 1, 2, and 3 to select resistors, or refer to the MAX1978 data sheet. 6) Connect the TEC module to OS1, OS2, THERM, and GND. Typical connections for most modules: * 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 Check module specifications before making connections. For lowest noise, connect the thermistor through shielded wire. 7) Connect a cable from the computer's parallel port to the MAX1978 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
Software 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): V Ratio = DAC REF where REF = 1.5V. The ratio must be a decimal number between zero and 1. Press Enter or click on the Update button to send the data to the DAC.
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5
MAX1978 Evaluation Kit Evaluates: MAX1978
The program starts with ratio = 0.5. This sets the DAC output to 0.75V, which corresponds to +25C. 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 for a typical NTC. 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 must 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 "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.
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.
INTO
CTLI
1.5V REF JU2 DAC SET POINT DIFOUT INT-
JU4 1.5V REF
FB+ 50R
1.5V REF
INTEGRATOR 20k THERM R 1.5V REF FBR PWM SECTION OS2 OS1 TEC+ N P TEC-
10k
50R CHOPPER AMP
MAX1978
10k THERMISTOR
Figure 1. Thermal-Loop Functional Diagram for the MAX1978 EV Kit 6 _______________________________________________________________________________________
MAX1978 Evaluation Kit Evaluates: MAX1978
Figure 2. Main Window for the MAX1978 EV Kit
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7
MAX1978 Evaluation Kit Evaluates: MAX1978
Figure 3. SPI Utility Showing the Settings to Communicate with the MAX1978 EV Kit 8 _______________________________________________________________________________________
MAX1978 Evaluation Kit Evaluates: MAX1978
VDD VDD GND OS1 C19 22F C20 OPEN
REF R8 OPEN C4 0.01F C5 OPEN ITEC VDD 39 38 37 MAXIP COMP ITEC FREQ 36
R1 CS 0.068 1%
CTLI REF
VDD
R2 49.9k 1% R3 100k 1% 42 GND
R4 SHORT (PC TRACE) R5 OPEN
R6 SHORT (PC TRACE) R7 OPEN
CS C1 4.7F 1
C2 1F 48 OS1 OS2 47 CS 46 REF
CTLI
C3 10F 44 43 VDD GND
OS2
45 CTLI
41 40 MAXV MAXIN
1 JU1 2 3
2 N.C. 3 L2 3H PGND2
N.C. 35 PGND1 LX1 PGND1 LX1 34 33 32
4 5
LX2 PGND2
C12 1F 6 VDD 7
L1 3H 31 VDD
CS
LX2
U1
PVDD2 C11 10F 8 N.C.
C7 1F C6 10F
MAX1978
PVDD1 30 N.C. LX1 29 28 VDD PVDD1 GND 27 26
VDD
9 10
LX2 PVDD2
R25 100k OT
1 2 3
11 SHDN JU3 12
VDD
OT UT INTOUT 13 14 INT15 C10 0.047F GND 16 R14 1M DIFOUT 17 REF FB18 FB+ 19 BFB20 REF R13 10k 0.1% C17 1F REF GND INT0 FB+ THERM C21 OPEN R10 R12 20k 69.8k 1% 1% R11 105k 1% BFB+ 21 AIN+ 22 AIN- AOUT 23 24
GND
25
R26 100k UT C9 10F CTLI JU2
ATO
R16 100k
R15 20k
C8 0.47F
R9 80.6k 1%
C16 OPEN
Figure 4. MAX1978 EV Kit Schematic (Sheet 1 of 2) _______________________________________________________________________________________ 9
MAX1978 Evaluation Kit Evaluates: MAX1978
REF REF R20 4.7k J1-4 1 R17 1k 2 Q1 R21 4.7k J1-2 1 VDD R18 1k 3 Q2 DB25 MALE RIGHT-ANGLE CONNECTOR J1-11 J1-3 1 J1-1 J1-5 J1-6 J1-7 J1-8 J1-9 J1-10 J1-12 J1-13 J1-14 J1-15 J1-16 J1-17 J1-18 J1-19 J1-20 J1-21 J1-22 J1-23 J1-24 J1-25 Q3 2 3 R19 1k 4 DIN R22 4.7k VDD DIN GND INV RFB 10 7 8 SW1 CLR 5 3 SCLK SCLK U2 VDD OUT 3 VDD CS C13 0.1F C14 0.1F FB+ 2 CS REF VDD 3 2 1 JU4 C15 0.1F SET_POINT GND VDD 1 2 3 R24 20k C18 OPEN
2
MAX5144
R23 1k
Figure 5. MAX1978 EV Kit Schematic (Sheet 2 of 2)
10
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MAX1978 Evaluation Kit Evaluates: MAX1978
Figure 6. MAX1978 EV Kit Component Placement Guide-- Component Side
Figure 7. MAX1978 EV Kit PC Board Layout (2oz Copper)-- Component Side
Figure 8. MAX1978 EV Kit PC Board Layout (2oz Copper)-- Ground Plane
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11
MAX1978 Evaluation Kit Evaluates: MAX1978
Figure 9. MAX1978 EV Kit PC Board Layout (2oz Copper)-- Power Plane
Figure 10. MAX1978 EV Kit PC Board Layout (2oz Copper)-- Solder Side
Figure 11. MAX1978 EV Kit Component Placement Guide (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.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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