Texas Instruments ADS848 EVM Series User Manual page 6

Digital Interface
Reference
Designator
Select onboard reference (REF3240)
SJP1
Select user-supplied reference at P1 pin 20
SJP2 Short voltage node +dc to U6 pin 3
SJP3 Set U6 operational amplifier minus rail supply to ground
Set U6 operational amplifier minus rail supply to –VCC
SJP4 Set U7 operational amplifier minus rail supply to ground
Set U7 operational amplifier minus rail supply to –VCC
SJP6 Set REFIN pin of ADS848x to on-chip (internal) reference voltage.
Set REFIN pin of ADS848x to reference selected by SJP1.
SJP7 Short voltage node –dc to U6 pin 2 via R35.
SJP8 Short voltage node +dc to U7 pin 3.
SJP9 Short –IN pin of U5 to ground at C45.
(1)
Indicates factory-installed option.
3.2 Reference
The ADS848x can operate with an external reference voltage in the range of 3 V up to 4.2 V. It generates
an on-chip 4.096-V reference voltage. The ADS848xEVM allows the user to select the external reference
voltage from three sources. The first option is to use the internally-generated 4.096 V from the ADC. The
other two options are to select from the onboard reference (U1) or a user-supplied voltage applied at pin
20 of P1. See Table 2
The reference voltage provides the scale factor for the conversion result. The input voltage is measured
against the reference voltage. It is imperative the reference voltage be clean, low-noise, and
well-decoupled.
The default configuration uses the internal on-chip reference.
4 Digital Interface
The ADS848xEVM is designed for easy interfacing to multiple platforms. The digital interface input and
output signals of the converter are on connectors P2, P3, and J6. These connectors are 0.1-inch center,
plug and socket connectors that allow the user to plug the ADS848xEVM into the various motherboard
interface boards from Texas Instruments, or connect via ribbon cable to a variety of user development
boards. Table 3 through
Description
Not connected
Reserved
Reserved
Address line 0
Address line 1
Address line 2
Reserved
Reserved
Convert Start
Interrupt pin
6 ADS848xEVM
Table 2. Analog Circuitry Jumper Configurations
Description
for solder jumper options for selecting from the various reference sources.
Table 6 list the connector pinouts and jumper settings.
Table 3. Pinout for Parallel Control Connector P3
Signal Name Connector Pin No.
DC_CS P3.1
N/A P3.3
N/A P3.5
A0 P3.7
A1 P3.9
A2 P3.11
N/A P3.13
N/A P3.15
DC_CONVST P3.17
INTC P3.19
Installed
Not Installed
Installed
Installed
Not installed
Installed
Not installed
Installed
Not installed
Installed
Installed
Not Installed
Signal Name
P3.2 +
P3.4 GND
P3.6 GND
P3.8 GND
P3.10 GND
P3.12 GND
P3.14 GND
P3.16 GND
P3.18 GND
P3.20 GND
SLAU186A – August 2006 – Revised September 2008
Submit Documentation Feedback
www.ti.com
Jumper Position
1-2 2-3
(1)
Not Installed
Installed
N/A
Not installed
(1)
Installed
Not Installed
(1)
Installed
(1)
Not installed
Installed
N/A
(1)
N /A
N/A
Description
Noninverting input channel
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground