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Power-Down, Mode, and Format Control
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Clock Source
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Power-Down, Mode, and Format Control
Figure 4. Switch S1
The ADS1278 has several pins to control the power-down of individual channels, and mode and format for
the digital interface. These pins are controlled on the EVM either through software or hardware (using
switches S10 and S11).
For users of the ADS1278EVM as a stand-alone module, these pins may be pulled high or low through
DIP switches S10 and S11. Refer to the
for complete details on these pins
and which state sets which options.
For use in the ADS1278EVM-PDK, the state of these pins is controlled by software, using the I
2
C port
expander on the EVM. When used in the ADS1278EVM-PDK, the DIP switches S10 and S11 must all be
switched so that they are down, toward the center of the board. The ADS1278EVM-PDK software will
check at startup to verify that these switches are set correctly, and will generate an error message if they
are not. However, it cannot detect if the switches are changed after startup.
CAUTION
When using the EVM as part of the ADS1278EVM-PDK, the DIP switches S10
and S11 must all be switched so that they are down, toward the center of the
board. Failure to do so may damage the EVM.
The ADS1278 clock can come from one of several sources: the onboard 27MHz crystal oscillator, a clock
supplied by a processor on the TOUT pin (J5.17), or an external clock source connected to J18.1 (ground)
and J18.2 (signal).
If the onboard 27MHz oscillator is selected, the device can be run in the high-speed mode, the
high-resolution mode, the low-power mode, or low-speed modes with CLKDIV set to 1. If the performance
of the device must be explored with CLKDIV set to 0 in the low-power and low-speed modes, an external
clock must be provided to the board, either using the TOUT connection or having an external clock source
connected to J18. The same condition is true if frequencies other than the 27MHz provided by the
onboard oscillator must be investigated.
SBAU129C – November 2007 – Revised July 2008
ADS1178EVM, ADS1278EVM, ADS1178EVM-PDK, and ADS1278EVM-PDK
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