Texas Instruments ADS1259EVM, Руководство пользователя

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10.1.5 PGA Configuration Tab
The PGA Configuration Tab (shown in Figure 34 ) has options that allow for control of much of the
PGA280.
Figure 34. PGA Configuration Tab
The first subsection of this tab sets control register 0 in the PGA280. First, there is a pull-down menu that
controls the input gain of the part, adjustable from 1/8V/V up to 128V/V with gains in factors of 2. A
second pull-down menu sets the output gain to either 1V/V or 1-3/8V/V.
In this subsection, another pull-down menu allows the user to set an external multiplexer value through
GPIO0-GPIO2. This option can be enabled with a push button and must also be set in the PGA GPIO tab.
Finally, control register 0 is written together with the Update PGA -Register 0 button. This feature allows
for simultaneous switching of gain and the external mux. If the Input Gain, Output Gain, or MUX Value
pull-down menus are changed, the Update PGA - Register 0 button becomes active and this button must
be clicked to proceed with the changes.
A pull-down menu allows for the synchronization of the PGA280 chopper. The chopper can be
synchronized to the internal clock of the PGA280 or to an external clock as supplied by the ADS1259. The
two parts can be connected on the right side of J1 when the jumper connects pins 2 and 3. In order for
this function to be enabled, the ADS1259 SYNCOUT pin must be enabled as found on the ADC
Configuration tab (see
Figure 32 ) with the SYNCOUT Enable.
The second subsection controls the Buffer of the PGA280. A pull-down menu allows for triggering the
buffer based on a write to a register. The buffer is turned off after a preset time. This time is variable and
can be written into the Buffer Timeout register in increments of 4µs, from 0µs to 252µs. To change the
time, enter a value between 0 and 252, and the plug-in rounds the result to the nearest value divisible by
four. Note that the buffer is only enabled with a change of the MUX value. For further information about
the use of the current buffer, see the PGA280 data sheet.
30 ADS1259EVM, ADS1259EVM-PDK SBAU163A – March 2010 – Revised April 2010
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