MAX134EVKITSYS1 Maxim Integrated, MAX134EVKITSYS1 Datasheet - Page 6

• Manufacturer Part Number: MAX134EVKITSYS1
• Description: Data Conversion IC Development Tools
• Manufacturer: Maxim Integrated
• Series: MAX133, MAX134r

MAX134 Evaluation Kit
There are actually two programs required for the MAX134
EV kit. The first is the program running in the MAXQ2000
microcontroller located on the board. This C program,
written using the Rowley CrossStudio compiler, can be
modified for use in digital multimeters with or without
the USB option. The second program is the application
program running on a PC. This program serves as the
user interface to monitor and control the operation of the
board. The various MAX134 registers can be controlled
and the conversion results displayed. Figure 1 shows the
user interface.
The application display of Figure 1 consists of several
sections. The value displayed on the board’s LCD dis-
play is in the upper left-hand corner. The raw MAX134
ADC reading and the last zero reading appear just
below. The displayed reading and raw ADC value are
updated at the end of each conversion. Values from
REG0–REG4 are displayed as the raw reading. The
Displayed_Reading is the Raw_reading minus the Zero_
reading. The demonstration program updates the zero-
reading display every 25th conversion—more frequently
than required by typical applications.
To the right of the reading values is the Range_Control
group box. By default, the system operates in the
autoranging mode, but the range can be manually set
using the Up/Down controls in the group box. The sys-
tem is returned to autoranging by pressing the Auto
Range button.
The position of the function-selector switch (SW1)
appears in the Function_Switch group box. The switch
is a 3-pole, 4-position rotary switch that configures the
MAX134 input for each function.
The Status_Bits group box displays the contents of the
MAX134 read-only status register. The register is read
at the end of each conversion. The most significant bit
(MSB) is always 1. The other three bits indicate continu-
ity, hold mode, and low battery. Refer to the MAX133/
MAX134 IC data sheet for more information.
The last values written to the MAX134 input registers
(Input_ Register_ 0–Input_ Register_ 4) appear down the
right side of the display. Each register bit toggles when
Table_2._Optional_Battery_Configuration
6_ _ _______________________________________________________________________________________
Detailed Description of Software
Three 1.5V cells
One 9V cell
BATTERY
Open
JU3
1-2
SHUNT_POSITION
JU4
1-2
2-3
the user clicks on the displayed bit value. Some configu-
rations, such as the AC mode and filter mode, require
multiple bits to be set for proper operation. Buttons are
provided in the User_ Modes group box to activate or
clear several MAX134 features. The AC_ Mode, Filter,
Input_/5, and Input_X2 buttons set or clear the MAX134
register bits as required. The Reset_ Ranges button
returns contents of REG0–REG4 to the default value for
all functions.
The Step_ Mode button in the User_ Modes group box
commands the MAXQ2000 to control the MAX134’s
conversion cycle using the Hold bit. This method allows
faster range changes when operating in the autorange
mode. Refer to the MAX133/MAX134 IC data sheet for a
detailed explanation of this procedure.
The MAX134 EV kit board consists of the MAX134 and
associated components, a MAXQ2000 microcontroller,
LCD display, level translators, an optoisolated MAX3420
USB controller, and power-supply circuits. A MAX4164
quad op amp generates the various supply voltages.
The MAX4164’s total supply current is less than using
multiple independent regulators.
Because the EV kit is normally connected to a PC, the
board is configured to operate from three AA batteries
for greater battery life. The batteries yield more than 100
hours of operation when connected to a PC. Powering
the optoisolators consumes much of the power in this
configuration. For a conventional digital multimeter, with-
out the USB connection to a host, the system can oper-
ate from a single 9V battery. Battery life can be improved
by reducing the MAXQ2000’s clock frequency.
To configure the board for 9V operation, set the power
switch (SW1) to the off position, remove the AA battery
cells, remove the shunt from JU3, and move the shunt
on JU4 to the 2-3 position (see Table 2). Damage to the
board can occur if the shunts are not set correctly before
connecting a 9V battery. Connect a 9V battery to the
BATT+ and BATT- terminals. To monitor the battery-drain
current, replace the shunt across JU2 with an ammeter
and remove the shunts from JU5 and JU6.
Detailed Description of Hardware
WITHOUT_A_PC
TYPICAL_BATTERY_CURRENT_(mA)
8.5
4.5
9V Operation
WITH_A_PC
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