Power Supplies
4
Power Supplies
J3 is the power-supply input connector.
lists the configuration details for J3. Analog inputs to the
ADC can be applied directly to the device (see
). An additional bipolar supply is needed to
power the bipolar amplifiers. For optimum noise performance, the external supplies (+VA and
–
VA) should
be used.
Table 3. J3 Configuration: Power-Supply Input
Pin No.
Pin Name
Function
Required
J3.1
+VA
+10V to +15V
Yes
J3.2
–
VA
–
10V to
–
15V
Yes
J3.3
+5VA
+5V analog supply
No
J3.4
–
5VA
–
5V analog supply
No
J3.5
DGND
Digital ground input
Yes
J3.6
AGND
Analog ground input
Yes
J3.7
+1.8VD
1.8V digital supply
No
J3.8
VD1
Unused
No
J3.9
+3.3VD
3.3V digital supply
Yes/Optional
J3.10
+5VD
+5V
Yes/Optional
The ADS833xEVM board requires several power supplies in order to power all of the installed
components. The onboard
drives the ADC input. In order to have the full common-mode input
range of 0V to 4.096V, the OPA211 requires
±
10V power supplies. The +10V power supply is also used to
power the
and
+5V regulator. The +5V derived from the low-dropout regulator (LDO)
powers the +VA analog voltage source for the ADS833x and the OPA350, which drives the reference
input.
The benefit of using a regulator to 5V ensures that the ADC and OPA350 are powered at the
same time as the input drive circuitry. Otherwise, applying power to the OPA211 and attempting to drive
the ADC inputs before powering on the ADS833x could cause potential damage or cause the ADC to
power up in an unknown state.
The digital voltage supply for the ADS833x is controlled by jumper JP7. By default, the jumper is in the 1-2
position, set to use the +5VD to power the ADC VBD supply. The +3.3VD supply is also an option.
5
Voltage Reference
The ADS833xEVM comes with an onboard Texas Instruments' REF5040. The reference voltage signal
can either be connected directly to the ADS8331/32 or filtered through a OPA350 unity gain buffer before
connection to the ADC. Jumpers JP5 and JP12 control whether the reference voltage signal is routed
through the OPA350 buffer or connected directly to the ADC.
It is recommended that the power supply be turned off while setting the jumper settings to control whether
or not the reference buffer is enabled. Doing so will verify that the EVM is not damaged as the OPA350 is
switched in or out. If you are unable to turn off the power, care must be taken with regard to the order that
JP5 and JP12 are changed when changing from the OPA350 buffer. When bypassing the OPA350, make
sure that the JP12 jumper is removed first, before the JP5 jumper is moved to the 2-3 position. This
procedure ensures that the reference signal is not driven from two different places.
The ADS833xEVM board is designed to either use the onboard 4.096V reference from the REF5040 or an
external source that can be connected to header J1. Jumper J6 is used to select the ADC reference
source.
6
Clock Source
The clock for the ADS8331/32 can come from one of two sources: the ADC internal oscillator or externally
using the SCLK (SCLK/2). Pin J2.3 is used for the SCLK input.
5
SBAU176A
–
August 2010
–
Revised May 2011
ADS833xEVM User
'
s Guide
Copyright
©
2010
–
2011, Texas Instruments Incorporated
