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MAX1280EVKIT

MAX1280 Evaluation Kit/Evaluation System

Maxim Integrated 

MAX1280 Evaluation Kit/Evaluation System

MAX1280 EV System

The MAX1280 EV system operates from a user-sup-

plied 7VDC to 20VDC power supply. Windows

98/2000/XP-compatible software running on a PC inter-

faces to the EV system board through the computer’s

serial communications port. See the Recommended

Equipment and Connections and Setup sections for

setup and operating instructions.

Description of Software

The evaluation software’s main window controls the

active control word bits, serial clock speed, and sam-

ple rate. It displays the voltage and output code for

each active channel, as well as some statistics of the

input signal. A separate graph window shows the data

changing in real time. The update rate is limited to

about 10 samples per second due to COM port band-

width limitations.

Controls

The control word is divided into several fields. To

change the active control word, drop down the appro-

priate field’s combo box and select the desired option.

If the QSPI™ clock is set to STOP, then configuration

data will not be sent until the READ button is clicked.

Statistics

The Minimum and Maximum fields show the highest and

lowest readings acquired. The Average field shows a run-

ning mean based on the equation ai = (k)(xi) + (1 - k)

(ai-1). The Clear button resets the statistics. To remove

offset errors, first apply 0V to the active input channel,

clear statistics, acquire some samples, and then check

Tare. This average offset voltage will now be subtracted

from all subsequent measurements.

Sampling

Choose the desired sampling rate (QSPI Clock), sam-

pling size (Sample! menu item), click Begin Sampling!

(in Sample! pop-up window). Sample size is restricted

to a power of 2 to permit FFT processing once the data

is saved to a file. After the samples have been collect-

ed, the data is automatically uploaded to the host and

is graphed. Once displayed, the data can optionally be

saved to a file.

Saving Graphs to Disk

Data in the real-time graph and in sampled data graphs

may be saved to a file. Only the raw output codes are

saved, but voltages may be inferred, based on the ref-

erence voltage and the maximum code value.

QSPI is a trademark of Motorola, Inc.

Scanning All Channels

To scan through all channels, select SCAN from the

INPUT menu.

Evaluating Shutdown

The evaluation software configures the 68HC16’s QSPI

submodule to continuously read data from the

MAX1280 into the 68HC16. The sample rate is con-

trolled by the QSPI clock. To evaluate power-saving

modes, these automatic updates must be stopped.

First, set the QSPI clock control to STOP. This reconfig-

ures the 68HC16’s QSPI submodule to stop driving the

serial clock. Second, in the evaluation software’s main

window, uncheck the Read Every...msec checkbox.

Next, choose the desired software power-down control

word, and click the Read button to send the new con-

figuration to the MAX1280. Or, if evaluating the hard-

ware shutdown, move jumper JU2 to the 2-3 position.

Sense the supply current by measuring the voltage

across resistors R9 and R10.

Reference Voltage

The evaluation software assumes a 2.5V reference volt-

age, unless otherwise specified. Refer to the MAX1280

IC data sheet for more information. To override this

value, type the new reference voltage into the Vref edit

box and click the Set Vref button.

Description of Hardware

U1, the MAX1280, is a high-speed, multichannel, 12-bit

data-acquisition system. Resistors R1–R8 and capaci-

tors C1–C8 form single-pole, lowpass anti-aliasing fil-

ters with a nominal 3ms time constant and approxi-

mately a 50kHz corner frequency. Jumper JU1 con-

nects the analog common (COM) to ground (GND).

C10 bypasses the bandgap reference, and C9 bypass-

es the analog-to-digital converter’s (ADC’s) voltage ref-

erence. When plugged into the 68HC16MODULE,

VDD1 and VDD2 are both powered by +5V. See the

MAX1280 EV kit schematic (Figure 1) and refer to the

MAX1280 IC data sheet.

Table 1. Jumper Functions

JUMPER POSITION

FUNCTION

Closed* COM is connected to GND

COM is disconnected from GND.

JU1

Open

All analog inputs, including COM,

must still be within the MAX1280’s

common-mode input range.

1-2*

JU2

2-3

*Default position.

Operate

Shutdown

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