Table 1. Keyboard Navigation Shortcuts
Low-Speed Data Logging
Readings can be taken automatically from user-selected
channels at regular intervals up to ten samples per sec-
ond by selecting “Scan Tool” from the “Window”menu.
The Channel Selection and Configuration group con-
trols which channels shall be scanned, and (where
applicable) configures each channel for bipolar and/or
differential input. The Bipolar and Differential controls
are disabled because the MAX115 inputs are always
bipolar and never differential. The scan rate combo box
controls the rate at which measurements are made.
Readings are displayed in the Recent Values text
area. Readings may optionally be recorded into a data
log file. Click on the “New Log” button to begin or end
data logging. This brings up the "Log File Format" dia-
log box. 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 subse-
quent line of the log file contains all enabled channels,
separated by commas, 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 corresponding Log menu commands. The pro-
gram continues to write data to the log file until the
Stop Log button is clicked.
One-Shot Read Tool
The One-Shot Read Tool allows direct control of the
A/D 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 A/D,
and performs one reading.
Power Cycling Tool
To reduce average supply current demand, the
MAX115 can be shut down between conversions. From
the “Window” menu, select “Power Cycling Tool”. The
amount of power savings depends primarily on how
long the part is off between conversions. The accuracy
of the conversions depends on the power-up delay, the
reference capacitor, and the time in power-down.
Adjust the off-time with the delay between samples
command. Adjust the on-time with the power-up delay
command.
Using an adequate power-up delay will ensure the
desired conversion accuracy 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.
The MAX115 EV kit software performs power-up by
writing a configuration word with the shutdown bit set.
After powering up, the power-up delay is executed to
allow time for the reference voltage to stabilize so that
an accurate measurement may be performed.
Sampling Tool
To sample data at rates up to 40ksps (samples per
second), select “Sampling Tool” from the “Window”
menu, make your selections, and click on the Start but-
ton. The timing delays may be adjusted as appropriate
to control the sample rate. The effective sample rate
can be estimated by taking the reciprocal of the sum of
the delay between samples, the power-up delay and
the conversion time. Sample size is restricted to a
power of two, so that the data can be processed by the
FFT tool. The sample size control controls the number
of samples collected on each selected channel. After
the samples have been collected, the data is automati-
cally uploaded to the host and is graphed. Once dis-
played, the data can optionally be saved to a file.
FFT Tool
The MAX115 evaluation software includes an FFT (Fast
Fourier Transform) 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 high-speed sampling tool. Then, select “FFT Tool”
from the “Window” menu. Check the output plots
desired, and click on the Start button. A data window-
ing function preprocesses a data sample before per-
forming the FFT. When the input signal is not synchro-
nized to the sampling clock, spectral energy appears
to leak into nearby frequency buckets. A suitable data
Evaluates: MAX115/MAX116
MAX115 Evaluation Kit
_______________________________________________________________________________________ 3
