Power Supplies
4
Power Supplies
The ADS7861 EVM board requires 5 V
DC
for both the analog and digital sections of the ADC. While filters
are provided for all power-supply inputs, optimal performance of the EVM requires a clean, well-regulated
power source. Positive 5-V
DC
power is applied to J3 and J4 (pin 1 referenced to pin 2). The ADS8361 and
ADS7863 each require 5 V
DC
for the analog supply located on J3, and 2.7 V to 5.5 V
DC
for the digital
supply located on J4.
An alternate power source can be applied via J6 located on the bottom side of the printed circuit board
(PCB). If a variable digital supply voltage is desired, completely remove the shunt jumper from W3. Apply
a 100-mA current limited dc voltage of not more than 5.5 V to J4.
NOTE:
The shunt jumper at location W3 should be placed across pin 2 and pin 3 for proper
operation of the ADS7861. This configuration is the factory default condition for all device
versions of the ADS7861/8361/7863EVM.
4.1
Reference Voltage
The ADS7861/8361/7863 can be configured to use its internal reference or external reference source
through jumper W1 (see schematic appended to this document for details). If an external reference is
desired, the shunt jumper on W1 should cover pins 2 and 3. The external reference is supplied through
header/socket J1 pin 20 (J1.20).
5
EVM Operation
Apply a current limited (150 mA max) 5-V
DC
source to J3 and J4 before connecting the analog input
signals and digital control signals.
5.1
Analog Input
The analog input source can be applied directly to header/socket J1 (top or bottom side) or through
optional amplifier and signal conditioning modules. The analog input level should not exceed 5 V
PP
.The
analog input range is from
–
VREF to VREF (0 V to 5 V
DC
) centered at 2.5 V.
5.2
Digital Control
The digital control signals can be applied directly to header/socket J2 (top or bottom side). The
ADS7861/8361/7863EVM can also be connected directly to a DSP interface board. Consult the respective
device product folder for a complete list of DSP interface cards and optional analog interface modules.
5.3
Default Jumper and Header Settings
Jumper W2 is provided to allow separation of the convert start (CONVST) and read (RD) signals. The
factory default condition for the EVM is to place a shunt jumper between pin 1 and pin 2 of W2. This
configuration combines signals RD and CONVST, which are applied to the ADC via pin J2.7. When W2 is
moved to pin 2 and pin 3, the RD signal is applied via pin J2.7 while CONVST is applied to pin J2.17.
Header J5 provides a way to access the M0, M1, and A1 control lines as well as the OUTB serial data.
Shunt jumpers are placed on pins 1 and 2, 3 and 4, and 5 and 6 of J5, which defaults M0, M1, and A0 to
logic low levels. Removing the jumpers allows these lines to go to logic high levels through the associated
pull-up resistors R12, R13, and R14. In the factory default configuration, the ADC converts the A0 and B0
inputs, and places AOUT serial data on pin J2.13, and BOUT serial data on pin J5.7.
4
ADS7861/8361/7863EVM
SLAU094A
–
October 2002
–
Revised May 2011
Copyright
©
2002
–
2011, Texas Instruments Incorporated
