19-1322; Rev 0; 10/97
MAX125/MAX126 Evaluation
Systems/Evaluation Kits
General Description
The MAX125/MAX126 evaluation systems (EV systems)
consist of a MAX125/MAX126 evaluation kit (EV kit) and
a Maxim 68HC16MOD-16WIDE microcontroller (µC)
module. The MAX125/MAX126 are high-speed, 8-chan-
nel, 14-bit data-acquisition systems with four simultane-
ous track/holds. Windows 3.1™/Windows 95™ software
provides a handy user interface to exercise the
MAX125/MAX126’s features.
Order the complete EV system for comprehensive eval-
uation of the MAX125/MAX126 with a personal comput-
er. Order the EV kit if you have already purchased the
µC module (68HC16MOD-16WIDE) with another Maxim
EV system or if you desire custom use in other µC-
based systems.
____________________________Features
o
Proven PC Board Layout
o
Complete Evaluation System Samples to 40ksps
o
Convenient Test Points Provided On Board
o
Data-Logging Software with FFT Capability
o
Fully Assembled and Tested
Evaluate: MAX125/MAX126
Ordering Information*
PART
MAX125EVKIT
MAX125EVB16
MAX126EVKIT
MAX126EVB16
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
INTERFACE TYPE
User Supplied
Windows Software
User Supplied
Windows Software
Stand-Alone EV Kits
The MAX125/MAX126 EV kits provide a proven PC
board layout to facilitate evaluation of the MAX125/
MAX126. The EV kits must be interfaced to appropriate
timing signals for proper operation. Apply dual power
supplies (±8V min, ±20V max) to connector P1, pin 5
(P1-5), and P1-9, with ground at P1-1. Connect the
active-low read strobe to P1-38, the write strobe to
P1-37, the chip selects to P1-35, and the convert-start
signal to P1-36 (Table 1 and Figure 1). Refer to the
MAX125/MAX126 data sheet for timing requirements.
*
The MAX125 software can be used only with the complete eval-
uation system (MAX125EVB16 or MAX126EVB16), which
includes the 68HC16MOD-16WIDE module together with the
MAX125EVKIT or MAX126EVKIT.
EV Systems
The MAX125/MAX126 EV systems operate from a user-
supplied +13V to +20V DC power supply. Windows
3.1/Windows 95 software running on an IBM PC inter-
faces to the EV system board through the computer’s
serial-communications port. The software can be oper-
ated with or without a mouse. Refer to the
Quick Start
section for setup and operating instructions.
MAX125EVB16
System Component List
PART
MAX125EVKIT
68HC16MOD-16WIDE
QTY
1
1
DESCRIPTION
MAX125 evaluation kit
68HC16 µC module with
16-bit parallel interface
MAX126EVB16
System Component List
PART
MAX126EVKIT
68HC16MOD-16WIDE
QTY
1
1
DESCRIPTION
MAX126 evaluation kit
68HC16 µC module with
16-bit parallel interface
Table 1. Power-Supply and Timing Signal
Connections
PIN
P1–1
P1–5
P1–9
P1–35
P1–36
P1–37
P1–38
POWER SUPPLY
SIGNAL
Ground
AVX
Positive Supply, +8V to +20V
AVX
Negative Supply, -8V to -20V
AVX
Chip
AVX Select
Convert-Start
AVX
Write
AVX Strobe
Read
AVX Strobe
Windows 3.1 and Windows 95 are trademarks of Microsoft Corp.
________________________________________________________________
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 408-737-7600 ext. 3468.
MAX125/MAX126 Evaluation
Systems/Evaluation Kits
Evaluate: MAX125/MAX126
MAX125EVKIT/MAX126EVKIT
Component List
DESIGNATION QTY
C1, C2, C4,
C5, C6, C9,
C10
C3, C8
C7
C11
P1, P2
R1, R6
R2–R5
R7, R8
U1
U2
U3
U4
U5
None
None
7
2
1
1
2
2
4
2
1
1
1
1
1
1
1
DESCRIPTION
0.1µF ceramic capacitors
10µF, 25V tantalum capacitors
4.7µF, 6.3V tantalum capacitor
100pF ceramic capacitor
2x20 right-angle connectors
100Ω, 1% resistors
10kΩ, 5% resistors
10Ω, 5% resistors
Maxim MAX125 or MAX126
78L05 voltage regulator
74HCT244
79L05 negative-voltage regulator
16MHz clock-oscillator module
PC board
Software disk:
MAX125 Evaluation Kit
Quick Start
Recommended Equipment
You will need the following equipment before you
begin:
•
A small DC power supply (+13V to +20V DC at
250mA)
•
•
•
An IBM PC-compatible computer capable of run-
ning Windows 3.1 or Windows 95
A spare serial-communications port, preferably a
9-pin plug
A serial cable to connect the computer’s serial port
to the Maxim 68HC16MOD-16WIDE module
Connections and Setup
Perform the following steps to evaluate the MAX125 or
MAX126:
1) Carefully connect the boards by aligning the two
40-pin headers of the MAX125/MAX126 EV kit with
the two 40-pin connectors of the 68HC16MOD-
16WIDE module. Gently press them together. The
two boards should be flush against each other.
2) Connect a +13V to +20V DC power source to the
µC module at the terminal block (J2) next to the
on/off switch, along the top edge of the µC module.
Observe the polarity marked on the board.
3) Connect a cable from the computer’s serial port to
the µC module. With 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.
4) Install the EV kit software on your computer by
running the
INSTALL.EXE
program on the floppy
disk. The program files are copied, and icons are
created for them in the Windows 3.1 program man-
ager (or the Windows 95 Start menu). The EV kit soft-
ware evaluates both the MAX125 and the MAX126.
5) Start the program by opening its icon in the pro-
gram manager (or Start menu).
6) The program prompts you to connect the µC mod-
ule and turn its power on. Slide SW1 to the on posi-
tion. Select the correct serial port and click OK. The
program automatically downloads
KIT125.B16
to
the module. The default device setting is for the
MAX125. If using the MAX126, select “MAX126” in
the device characteristics dialog box and click on
“apply.”
List of Files in MAX125 EV Kit
FILE
INSTALL.EXE
MAX125.EXE
MAX125.HLP
KIT125.B16
MAX125.INI
UNINST.EXE
FUNCTION
Installs EV kit files onto your computer
Application program
Help file
Loads software into the 68HC16 µC
Program settings
Removes EV kit files from your computer
2
_______________________________________________________________________________________
MAX125/MAX126 Evaluation
Systems/Evaluation Kits
7) Apply input signals to the inputs labeled
CH1A–CH4A at the bottom edge of the MAX125/
MAX126 EV kit board. Observe the readout on the
screen.
You may optionally record readings into a data-log file.
Click on the “New Log” button to begin or end data log-
ging. The “Log File Format” dialog box is displayed.
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 contains all enabled channels, separated by com-
mas, tabs, or spaces (previously selected in the “Log
File Format” dialog box). Once a log file has been
opened, it can be paused or resumed with the corre-
sponding Log menu commands. The program contin-
ues to write data to the log file until the “Stop Log”
button is clicked.
Evaluate: MAX125/MAX126
Detailed Description of Software
The MAX125/MAX126 digitize up to four inputs from
either the A or the B input bank. Conversion time is
determined by the number of enabled inputs. The soft-
ware collects samples at a maximum throughput of
40ksps (one channel) and 26ksps (four channels). The
various program functions are grouped into dialog
boxes, which are accessible from the Window menu on
the main menu bar.
One-Shot Read Tool
The “One-Shot Read Tool” allows direct control of the
analog-to-digital converter (ADC) configuration. Select
the channel and mode of operation to update the
“Control Byte” display. Or, change the “Control Byte”
bits directly and observe the change in the “Channel
Selection” control. The “Read Now” button writes the
configuration information to the ADC and performs one
reading.
Keyboard Navigation
If a mouse or other pointing device is not available, use
the following keyboard shortcuts (Table 2):
•
Press ALT+W to display the Window menu, and
then select a tool window.
•
Press the TAB key to select controls within the
selected tool window.
•
Activate buttons by pressing the spacebar.
•
Use the up/down arrow keys for check boxes, radio
buttons, and combo boxes.
Power Cycling Tool
To reduce average supply current demand, the
MAX125/MAX126 can be shut down between conver-
sions. From the Window menu, select “Power Cycling
Tool.” The amount of power saved depends primarily
on how long the part is off between conversions.
Conversion accuracy depends on the power-up delay,
reference capacitor, and time in power-down. Adjust
the off-time with the “Delay Between Samples” com-
mand. Adjust the on-time with the “Power-Up Delay”
command.
Using an adequate power-up delay ensures that the
desired conversion accuracy is achieved during power-
cycling modes. The reference must be allowed enough
time to stabilize before the measurement is performed.
Start with zero power-up delay, and increase the delay
time until no further change in accuracy is observed. The
power-up delay requirement depends on the value of the
reference capacitor and the off-time (delay between
samples).
The MAX125/MAX126 EV kit software performs power-
up by writing a configuration word with the shutdown
bit cleared. After power-up, the power-up delay is exe-
cuted to allow time for the reference voltage to stabilize
so that an accurate measurement can be performed.
Scan Tool
You can automatically take readings at regular intervals
up to 10 samples per second from user-selected chan-
nels by selecting Scan Tool from the Window menu.
The “Channel Selection and Configuration” group con-
trols which channels will be scanned. The “Bipolar and
Differential” controls are disabled because the
MAX125/MAX126’s transfer function is bipolar.
The “Scan Rate” combo box controls the rate at which
measurements are made. Readings are displayed in
the “Recent Values” text area.
Table 2. Keyboard-Navigation Shortcuts
KEY
TAB
ALT+W
ALT+space
ALT+minus
Spacebar
ALT+PrintScreen
FUNCTION
Selects next control
Window menu
System menu of main program window
System menu of child window
Clicks on the selected button
Copies the image of the main window
onto the clipboard
_______________________________________________________________________________________
3
MAX125/MAX126 Evaluation
Systems/Evaluation Kits
Evaluate: MAX125/MAX126
Sampling Tool
To sample data at rates up to 40ksps, select “Sampling
Tool” from the Window menu, make your selections,
and click on the Start button. Adjust the timing delays
as appropriate to control the sample rate. Estimate the
effective sample rate by taking the reciprocal of the
sum of the delay between samples, the power-up
delay, and the conversion time. Sample size is restrict-
ed to a power of two so that the “Fast Fourier
Transform” (FFT) tool can process the data. “Sample
Size” controls the number of samples collected on
each selected channel. After the samples have been
collected, the data is automatically uploaded to the
host and graphed. Once displayed, the data can
optionally be saved to a file.
Changing the Reference Voltage
The EV kit software assumes a 2.5V reference voltage,
unless otherwise specified. Apply an external 2.5V ref-
erence to the REFIN pad to overdrive the internal refer-
ence. See the MAX125/MAX126 data sheet for more
information. From the Window menu, select “Device
Characteristics.” Next, type the new reference voltage
into the “Reference Voltage” edit box.
Detailed Description
of Hardware
The ADC (U1) is an 8-channel, 14-bit data-acquisition
system with four simultaneous track/holds. Linear regu-
lators U2 and U4 provide clean analog ±5V power sup-
plies for the ADC. R8 and C1 filter digital noise out of
the analog power supply. U3 isolates the
CS, RD, WR,
and CONVST signals from the main system bus to fur-
ther prevent digital noise from entering the ADC. R7
and C11 filter the TTL clock oscillator to prevent over-
shoot at the CLK input.
The MAX125/MAX126’s chip-select (CS) is memory-
mapped to location 7E000 on the 68HC16 module. This
location is used for writing configuration bytes and
reading data. The convert-start (CONVST) signal is also
memory-mapped and is asserted for one memory-
access cycle when memory location 7E800 is
accessed. The MAX125/MAX126’s interrupt (INT) out-
put triggers an interrupt on the 68HC16 through the
input capture vector.
FFT Tool
The EV software includes an FFT tool that can display
the spectral content of data collected with the high-
speed sampling tool.
To view the spectral content of a waveform, first select
a data sample that was previously collected with the
“Sampling Tool.” Then select “FFT Tool” from the
Window menu. Check the output plots desired and
click on the Start button.
A data-windowing function preprocesses the data
sample before performing an FFT.
1)
When the input sig-
nal is not synchronized to the sampling clock, spectral
energy appears to leak into nearby frequency buckets.
A suitable data window tapers the raw data to zero
amplitude at the beginning and end, reducing this spec-
tral leakage.
Measuring Supply Current
To monitor supply current, measure the voltage across
resistor R1 (for the +5V supply) or R6 (for the -5V sup-
ply). These resistors are 100Ω ±1%, so every 1mV
across R1 or R6 represents 10µA of supply current.
Device Characteristics
The “Device Characteristics” dialog box contains para-
meters that are not expected to change often. The
device selection is used to select between the MAX125
and the MAX126.
Table 3. Troubleshooting Guide
PROBLEM
•
•
No output measurement.
System seems to report
zero voltage or fails to
make a measurement.
CORRECTIVE ACTIONS
Check the +5V and -5V sup-
ply voltages.
Check the 2.5V REFOUT ref-
erence voltage using a digi-
tal voltmeter.
Use an oscilloscope to verify
that the 16MHz clock is run-
ning and that the conver-
sion-start signal is being
strobed.
Evaluating the MAX126
The MAX125 software can evaluate the MAX126 direct-
ly. From the Window menu, select “Device Charac-
teristics.” Next, change the device type from MAX125
to MAX126. This tells the program that the input voltage
span is ±V
REF
instead of ±2V
REF
.
•
1)
For more information on the FFT and data-windowing functions, refer to W.H. Press, et al.,
Numerical Recipes in Pascal: The Art of
Scientific Computing,
Cambridge University Press, 1989, ISBN 0-521-37516-9.
4
_______________________________________________________________________________________
P1-5
8
IN
OUT
GND
GND
N.C.
17
P2-1
D0/A0
D1/A1
D2/A2
D3/A3
D4
D5
D6
D7
D8
CH4A
32
CH4A
CLK
14
R7
10Ω
25
CH4B
33
CH4B
CH3A
34
CH3A
+5V
CH3B
35
CH3B
CH2B
1
CH2B
CH2A
2
CH2A
CH1B
3
CH1B
CH1A
CH1A
P2-2
P2-3
P2-4
P2-5
P2-6
P2-7
16
15
14
13
D9
D10
D11
D12
D13
INT
7
REFOUT
C6
0.1µF
REFIN
6
C5
0.1µF
REFOUT
C7
4.7µF
6.3V
8
CONVST
DGND
AVSS
31
AGND
AGND
36
REFIN
JU1
-5V
12
11
10
9
30
19
20
21
22
23
24
DVDD
4
AVDD
5
4
3
C2
0.1µF
C1
0.1µF
R8
10Ω
2
GND
GND
N.C.
+5V
7
C4
0.1µF
6
5
C3
10µF
25V
1
R1
100Ω
U2
LM78L05ACM
+5V
P1-6
Figure 1. MAX125 EV Kit Schematic
U3A
1
OE
2
A0
Y0
Y1
Y2
Y3
P2-14
P1-20
28
RD
WR
CS
27
+5V
R3
10k
+5V
R2
10k
18
29
26
R4
10k
+5V
9
7
5
3
12
R5
10k
P2-13
14
P2-12
16
+5V
P2-11
A1
A2
A3
74HCT244
4
6
8
18
P2-10
P2-9
P2-8
+12V
CS7/7E000
P1-35
CS7
U1
CLK
P1-38
RD
1
U5
16MHz
8
7
OSCILLATOR
C11
100pF
P1-37
WR
MAX125
MAX126
CS8/7E800
P1-36
U3B
19
OE
A0
Y0
Y1
Y2
Y3
A1
A2
A3
74HCT244
11
13
15
17
CS8
R6
100Ω
8
N.C.
IN
IN
GND
7
C8
10µF
25V
C9
0.1µF
6
5
OUT
IN
IN
N.C.
1
2
3
4
U4
LM79L05ACM
P1-1
P1-2
-5V
C10
0.1µF
P1-3
P1-4
GND
P1-9
Evaluate: MAX125/MAX126
_______________________________________________________________________________________
-12V
MAX125/MAX126 Evaluation
Systems/Evaluation Kits
5
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