Texas Instruments ADS794xEVM, User Manual, Page: 9 / 31

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EVM Operation
9 SBAU194B – August 2011 – Revised September 2017
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Copyright © 2011–2017, Texas Instruments Incorporated
ADS794xEVM and ADS794xEVM-PDK
5 EVM Operation
This section provides information on the analog input, digital control, and general operating conditions of
the ADS794xEVM without the MMB0 motherboard. Software operation is presented in
Section 7 .
5.1 Analog Input
The ADS794xEVM offers three different analog input modes, selectable with jumper J6 and the type of
input signal. Note that the ADS794x converter by itself only allows dc-coupled unipolar signals. The two
additional input modes are available because OPA836 operational amplifiers drive the analog inputs. It is
preferable for external signal drivers or filters to have low output impedance to reduce gain errors.
Mode 1: DC-Coupled Unipolar Inputs (J6 Closed)
DC-coupled unipolar signals are typically produced by single-supply signal drivers. To allow dc-coupled
unipolar signals, J6 should be closed. This mode allows an input signal range from 0 V to V
REF
for all EVM
analog inputs. In this mode, the voltage read at the ADC is equal to (V
REF
– V
IN
).
Mode 2: DC-Coupled Bipolar Inputs (J6 Open)
DC-coupled bipolar signals are typically produced by dual-supply signal drivers. To allow dc-coupled
bipolar signals, J6 should be open. This mode allows an input signal range from –V
REF
/2 to +V
REF
/2 for all
EVM analog inputs. In this mode, the voltage read at the ADC is equal to (V
REF
/2 – V
IN
).
Mode 3: AC-Coupled Inputs (J6 Closed)
AC-coupled signals are typically produced by high-pass filters. To allow ac-coupled bipolar signals, J6
should be closed. This mode allows an input signal range from –V
REF
/2 to +V
REF
/2 for all EVM analog
inputs. In this mode, the voltage read at the ADC is equal to (V
REF
/2 – V
IN
).
5.2 Digital Control
The digital control signals can be applied directly to the P1 header (top or bottom side). The modular
ADS794xEVM can also be connected directly to a DSP or microcontroller interface board, such as the
5-
6K Interface or HPA-MCU Interface boards available from Texas Instruments, or the MMB0 if purchased
as part of the ADS794xEVM-PDK. For a list of compatible interface and/or accessory boards for the EVM
or the ADS794x, see the relevant product folder on the TI web site.