Datasheet

3.2 Reference
4 Digital Interface
Digital Interface www.ti.com
Table 2. Analog Circuitry Jumper Configurations
Jumper Position
Reference
Designator Description 1-2 2-3
Select onboard reference (REF3240) Installed
(1)
Not Installed
SJP1
Select user-supplied reference at P1 pin 20 Not Installed Installed
SJP2 Short voltage node +dc to U6 pin 3 Installed N/A
SJP3 Set U6 operational amplifier minus rail supply to ground Installed Not installed
Set U6 operational amplifier minus rail supply to –VCC Not installed Installed
(1)
SJP4 Set U7 operational amplifier minus rail supply to ground Installed Not Installed
Set U7 operational amplifier minus rail supply to –VCC Not installed Installed
(1)
SJP6 Set REFIN pin of ADS848x to on-chip (internal) reference voltage. Installed
(1)
Not installed
Set REFIN pin of ADS848x to reference selected by SJP1. Not installed Installed
SJP7 Short voltage node –dc to U6 pin 2 via R35. Installed N/A
SJP8 Short voltage node +dc to U7 pin 3. Installed
(1)
N /A
SJP9 Short –IN pin of U5 to ground at C45. Not Installed N/A
(1)
Indicates factory-installed option.
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 for solder jumper options for selecting from the various reference sources.
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.
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 Table 6 list the connector pinouts and jumper settings.
Table 3. Pinout for Parallel Control Connector P3
Description Signal Name Connector Pin No. Signal Name Description
Not connected DC_CS P3.1 P3.2 + Noninverting input channel
Reserved N/A P3.3 P3.4 GND Ground
Reserved N/A P3.5 P3.6 GND Ground
Address line 0 A0 P3.7 P3.8 GND Ground
Address line 1 A1 P3.9 P3.10 GND Ground
Address line 2 A2 P3.11 P3.12 GND Ground
Reserved N/A P3.13 P3.14 GND Ground
Reserved N/A P3.15 P3.16 GND Ground
Convert Start DC_CONVST P3.17 P3.18 GND Ground
Interrupt pin INTC P3.19 P3.20 GND Ground
ADS848xEVM 6 SLAU186A – August 2006 – Revised September 2008
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