EVM Operation
The ADS833xEVM has several hardware options to allow users to test the ADC under certain conditions.
On the PCB, jumpers are used to add or remove op amps to drive the reference line and the ADC input.
By default, the EVM is configured to use the REF5040 to create a 4.096V signal for the reference voltage;
it is buffered through an OPA350. The analog inputs also have the option to use an onboard op amp to
properly drive the ADC input. The OPA211 in a unity-gain configuration is placed between the MUX
OUT
and ADC
IN
pins to give an example of how to drive any of the input channels using a single op amp. All of
the hardware options found on the ADS833xEVM are controlled through jumpers and switches.
Jumper JP3 controls whether the OPA211 unity-gain buffer, used to drive the analog input signals, is
enabled or bypassed. By default, JP3 is in the 1-2 position to route the signal through the op amp buffer
and RC filter before reaching the converter input. Moving the jumper to the 2-3 position bypasses the
OPA211 and routes the input signal only through a first-order, low-pass filter.
Jumper JP4 is used to route the FS/CS signal from the ADS8331/32 to either pin J2.1 or J2.7 and J2.9.
By default, the jumper is in the 2-3 position, routing the signal to J2.7 and J2.9.
As mentioned previously, the ADS833xEVM has the option to use an onboard OPA350 to drive the
reference voltage. Two jumpers are used to route the reference voltage through the op amp. JP5 routes
the signal through the OPA350 and JP12 connects the op amp output to the ADC reference voltage. Both
jumpers must be properly placed in order to use or bypass the reference buffer. By default, JP5 is in the
1-2 position and JP12 is installed, routing the reference voltage through the OPA350 and connecting it to
the ADC reference. If JP12 is removed and JP5 is in the 2-3 position, the OPA350 can be bypassed. See
the
section for more information on bypassing the op amp.
JP6 selects the reference source. By default, JP6 is in the 1-2 using the REF5040 installed on the EVM. If
an external reference voltage is needed, simply set JP6 to the 2-3 position. An external reference signal
can then be applied to pin 20 on the J1 header.
Jumper JP7 selects between using a +3.3VD or +5VD voltage to power the +VBD signal of the ADC. By
default, the jumper is in the 1-2 position to use +5VD.
JP9 allows you to use an external source to trigger the CONVST. By default, the jumper is installed
routing the CONVST signal to the J2 header. If the jumper is removed, the CONVST signal can be
controlled via an external source to the jumper pin.
Additionally, there is one switch used to control the RESET signal of the ADC. S1 is a pushbutton switch
used to perform a hardware reset of the ADC.
lists the jumpers found on the EVM and the factory default conditions for each of the configurable
jumpers.
Table 4. List of Configured Jumpers
Jumper
Default Position
Switch Description
Enable the OPA211 buffer amplifier to drive ADC
JP3
1-2
inputs
JP4
2-3
Route CS signal to J2.7 and J2.9
Enable the OPA350 buffer amplifier to drive
JP5
1-2
reference voltage
JP6
1-2
Use onboard REF5040 for ADC reference
JP7
1-2
+VBD to +5V
JP9
Installed
Connect CONVST signal to J2 header
JP12
Installed
Route reference signal from OPA350 to ADC
SW1
N/A
Pushbutton switch to control Reset signal
7
SBAU176A
–
August 2010
–
Revised May 2011
ADS833xEVM User
'
s Guide
Copyright
©
2010
–
2011, Texas Instruments Incorporated
