Maxim MAX1202 Manual
Maxim MAX1202 is a low-power, +5V, 8-channel, 12-bit analog-to-digital converter (ADC) that connects directly to 3V and 5V microprocessors (µPs). It is a complete, 8-channel data-acquisition system consisting of a MAX1202 evaluation kit (EV kit) and a Maxim 3V 68L11D microcontroller (µC) module. The MAX1202 EV kit and EV system can also be used to evaluate the MAX1203. The device is fully assembled and tested, and comes with a convenient on-board test points and data-logging software. It can be used for applications such as data acquisition, process control, and medical instrumentation.
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19-1197; Rev 0; 3/97
6811D MODULE
AVAILABLE
MAX1202 Evaluation Kit
_______________General Description
The MAX1202 evaluation system (EV system) is a complete, 8-channel data-acquisition system consisting of a
MAX1202 evaluation kit (EV kit) and a Maxim 3V
68L11D microcontroller (µC) module.
The MAX1202 is a low-power, +5V, 8-channel, 12-bit analog-to-digital converter (ADC) that connects directly to 3V and 5V microprocessors (µPs). Windows 3.1™/
Windows 95™ software provides a handy user interface to exercise the MAX1202’s features.
Order the EV system for comprehensive evaluation of the MAX1202 using a personal computer. Order the EV kit if you have already purchased the 68L11D µC module with a previous Maxim EV system, or for custom use in other µC-based systems.
The MAX1202 EV kit and EV system can also be used to evaluate the MAX1203. Simply order a free sample of the MAX1203BCPP along with the MAX1202 EV kit. For
3V-only applications, refer to the MAX147 data sheet.
____________________________Features
♦ Proven PC Board Layout
♦ Complete Evaluation System
♦ Convenient On-Board Test Points
♦ Data-Logging Software
♦ 3V/5V Logic Interface
♦ Fully Assembled and Tested
______________Ordering Information
PART
MAX1202EVKIT-DIP
MAX1202EVL11-DIP
TEMP. RANGE
0°C to +70°C
0°C to +70°C
BOARD TYPE
Through-Hole
Through-Hole
MAX1202EVL11
___________System Component List
PART
MAX1202EVKIT-DIP
68L11DMODULE
QTY
1
1
DESCRIPTION
MAX1202 Evaluation Kit
68L11D µC Module
____________________Component List
DESIGNATION
C1–C8, C13
C9, C10, C11,
C14, C15
C12
J1
JU1, JU2
JU3
JU4
R1–R8
TP1
U1
U2
U3
None
None
QTY
9
DESCRIPTION
0.01µF ceramic capacitors
5
1
1
0
1
2
1
1
8
1
1
1
1
1
0.1µF ceramic capacitors
4.7µF, 10V tantalum capacitor
2 x 20 right-angle socket
3-pin jumper blocks
2-pin jumper block
Open
300
Ω
, 5% resistors
8-pin header
Maxim MAX1202BCPP
20-pin socket
Maxim ICL7660CPA
78L05 voltage regulator
PC board
Software disk,
“MAX1202 EVALUATION KIT”
_____MAX1202 Stand-Alone EV Kit
The MAX1202 EV kit provides a proven PC board layout to facilitate evaluation of the MAX1202. It must be interfaced to appropriate timing signals for proper operation. Refer to the MAX1202 data sheet for timing requirements.
Cut JU4 and apply the +5V analog supply between the
+5V pad and the pad marked GND. Connect the
VLOGIC pad to the microprocessor's power supply. Set
JU1 to the 2-3 position (V
SS
= -5V) to allow input signals between ±4V (Table 1).
Windows is a registered trademark of Microsoft Corporation.
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAX1202 Evaluation Kit
______________MAX1202 EV System
The MAX1202 EV system operates from a usersupplied 9V to 15V DC power supply. The Maxim
68L11D 3V µC board uses a MAX667 linear regulator to generate the 3V logic supply. The MAX1202 board uses a 78L05 linear regulator to generate its own 5V analog supply. No level translators are necessary because the MAX1202 VL pin is connected to the 3V logic supply.
Quick Start
1) Install the MAX1202 EV kit software on your computer by running the INSTALL.EXE program on the floppy disk. The Windows 3.1 Program Manager (or the
Windows 95 Start Menu) copies the program files and creates icons for them.
2) Check the jumper settings on the EV board. Refer to
Tables 1 and 2.
3) Carefully connect the boards by aligning the EV kit’s
40-pin header with the µC module’s 40-pin connector. Gently press them together. The two boards should be flush against one another.
4) Connect a 9V to 15V DC power source to the µC module at the terminal block located next to the on/off switch, in the upper-right corner of the µC module. Observe the polarity marked on the board.
5) Connect a cable from the computer’s serial port to the µC module. If using a 9-pin serial port, use a straight-through, 9-pin female-to-male cable. If the only available serial port uses a 25-pin connector, a standard 25-pin to 9-pin adapter is required. The EV kit software checks the modem status lines (CTS,
DSR, DCD) to confirm that the correct port has been selected.
6) Start the MAX1202 program by opening its icon in the Program Manager (or Start Menu).
7) The program will prompt you to connect the µC module and turn its power on. Slide SW1 to the on position. Select the correct serial port and click OK.
The program automatically downloads KIT1202.L11
to the module.
8) Apply input signals to the CH0–CH7 inputs at the right edge of the MAX1202 EV board. Observe the readout on the screen.
Table 1. Jumper Functions
∫
JUMPER STATE FUNCTION
JU1
1-2
2-3
Open
1-2
V
SS tied to GND
V
SS tied to -5V
V
SS must be supplied by the user.
SHDN tied to GND; power-down
JU2
2-3
SHDN tied to +5V; internal compensation
Open
SHDN floating; external compensation
Closed
REFADJ = +5V; VREF must be supplied by the user.
JU3
JU4
Open
REFADJ = open; VREF = 4.096V
internal reference (MAX1202)
Closed
(default trace)
Open
Current-sense jumper. The
MAX1202 draws its +5V analog supply through this trace.
Do not operate kit with JU4 open.
Table 2. Default Jumper Settings
JUMPER
JU1
JU2
JU3
JU4
DEFAULT
STATE
2-3
2-3
Open
Closed
FUNCTION
V
SS tied to -5V
SHDN tied to +5V
REFADJ = open; VREF = 4.096V
internal reference (MAX1202)
The MAX1202 draws its +5V analog supply through this trace.
Evaluating the MAX1203
To evaluate the MAX1203, turn off the power to the EV kit, close JU3, and replace U1 with a MAX1203BCPP.
Connect the external voltage reference to the VREF pad. No other hardware changes are necessary. Refer to the section Changing the Reference Voltage.
2 _______________________________________________________________________________________
MAX1202 Evaluation Kit
__Detailed Description of Software
Shutdown Power Cycling
The MAX1202 can be shut down between conversions to reduce average supply-current demand. From the
“Power” menu, select full power-down (FULLPD) or fast power-down (FASTPD) mode. In fast power-down mode, the bandgap reference remains active. The amount of power saved depends primarily on how long the part is off between conversions. The conversion accuracy depends on the power-up delay, the reference capacitor, and the time in power-down. Adjust offtime with the “Delay Between Samples” command.
Adjust on-time with the “Power-Up Delay” command.
Using an adequate power-up delay ensures conversion accuracy during power-cycling modes. The reference must be allowed enough time to stabilize before the measurement is performed. The “Power-Up Delay” command controls power-up delay. Increase the delay until accuracy is constant. The power-up delay requirement depends on the off-time (delay between samples) and the value of the reference capacitor (C12).
The MAX1202 EV kit software performs power-up by starting a conversion in FASTPD mode and discarding the reading. FASTPD mode turns on the reference, but leaves the MAX1202’s other circuitry powered down.
An accurate reference-voltage measurement can be performed after the power-up delay is complete.
The MAX1203 requires an external reference, so
FULLPD mode can always be used, assuming the external reference is always stable when measurements are performed. In this case, set power-up delay to 0.
Measuring Supply Current
On the EV board, the MAX1202 draws all of its +5V analog power through jumper JU4, which is wired closed when the board is shipped from the factory. To measure the MAX1202’s supply current, modify the board (with the power off) by cutting jumper JU4 and connecting a current meter across JU4.
Low-Speed Data Logging
The RS-232 serial link limits the data-logging sample rate to no more than 10 samples/sec. The “Log” menu can be used to write data to a user-specified file in comma-spaced-value text format. From the “Log” menu, choose “Select Channels”, and select the channels you want to log. Then choose the “New Log File” command from the “Log” menu. Once a log file has been opened, it can be paused or resumed with the
“Pause” command. One complete line of data is written after all enabled channels have been sampled. The first line of the log file contains the column headings. Each subsequent line of the log file contains all enabled channels, separated by commas, tabs, or spaces. The program continues to write data to the log file until the
“Done” command is selected from the “Log” menu.
High-Speed Data Sampling
The high-speed sampling commands can be used for sampling rates over 10 samples/sec. Data can be collected from any single channel at high speed, using the commands on the “Sample” menu. First select the number of samples. Then set the sampling rate either by inserting a delay between samples, or by choosing one of the preset sample rates. Use the “Collect” command to begin collecting data. After the samples are collected, the data is automatically uploaded to the host and graphed. Additionally, the data can be saved to a file.
Changing the Reference Voltage
The MAX1202 EV kit software assumes a 4.096V reference voltage, unless otherwise specified. The reference-voltage assumption can be changed using “Set
Reference Voltage” under the “Device” menu.
If an external reference is used, it must have a temperature coefficient of 20ppm/°C or less to achieve accuracy to within four LSBs over the 0°C to +70°C range. For 12bit accuracy over this range, the reference must have a temperature coefficient of 4ppm/°C or less.
Detailed Description
________________________of Hardware
Components
The MAX1202 (U1) is an 8-channel, 12-bit, low-power analog-to-digital converter (ADC) with serial interface and shutdown. R1–R8 and C1–C8 are anti-aliasing input filters. The analog supply rails are VDD, VSS, and
GND. The digital interface is powered by the VL pin.
The SHDN jumper controls hardware shutdown and selects internal/external-compensation mode. Refer to the MAX1202 data sheet for more information.
The ICL7660 (U2) is a charge pump that converts +5V to -5V for V
SS
.
The 78L05 (U3) is a +5V linear regulator that provides a clean analog supply for the MAX1202.
Input Filtering
The MAX1202 EV kit has an RC filter on each input with a time constant (
τ
) of approximately 3µs (R = 300
Ω
,
C = 0.01µF). The MAX1202’s acquisition time with a
2MHz clock is 1.5µs. The RC filter’s settling time can increase the acquisition time required for full accuracy when switching input channels.
_______________________________________________________________________________________ 3
MAX1202 Evaluation Kit
+5V
VSS
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
R1
300
Ω
R2
300
R3
300
R4
300
R5
300
R6
300
R7
300
R8
300
Ω
Ω
Ω
Ω
Ω
Ω
Ω
C1
0.01
µ
F
1
CH0
2
CH1
C2
0.01
µ
F
3
CH2
C3
0.01
µ F
4
CH3
C4
0.01
µ F
5
CH4
C5
0.01
µ
F
6
CH5
C6
0.01
µ
F
7
CH6
C7
0.01
µ
F
8
CH7
C8
0.01
µ
F
9
VSS
C11
0.1
µ
F
+5V
1
2
3
JU1
V+
8
1
N.C.
U2
6
LV
3
GND
ICL7660 VOUT
5
2
CAP+
CAP-
4
OSC
7
C10
0.1
µ
F
SHDN
-5V
C9
0.1
µ
F
+5V
3
2 1
JU2
10
SHDN
U1
MAX1202
V
DD
20
SCLK
19
CS
18
DIN
17
SSTRB
16
DOUT
15
VL
14
GND
13
REFADJ
12
REF
11
C15
0.1
µ F
C14
0.1
µ
F
JU3
C12
4.7
µ
F
10V
TEST POINTS
JU4
C13
0.01
µ
F
+5V
1
U3
78L05
OUT IN
3
+9V TO
+15V
COM
2
J1-5
J1-6
VLOGIC
GND
REFADJ
VREF
J1-37
J1-31
J1-36
J1-29
J1-35
J1-7
J1-8
J1-1
J1-2
J1-3
J1-4
Figure 1. MAX1202 EV Kit Schematic
4 _______________________________________________________________________________________
MAX1202 Evaluation Kit
1.0"
Figure 2. MAX1202 EV Kit Component Placement Guide—
Top Silkscreen
1.0"
Figure 3. MAX1202 EV Kit PC Board Layout—Component Side
1.0"
Figure 4. MAX1202 EV Kit PC Board Layout—Solder Side
_______________________________________________________________________________________ 5
MAX1202 Evaluation Kit
Listing 1. MAX1202 Pseudo-Code Example
6 _______________________________________________________________________________________
MAX1202 Evaluation Kit
Listing 2. Bit-Banging Substitute for SPI Port
_______________________________________________________________________________________ 7
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