Datasheet

ADS7863
SBAS383E –JUNE 2007–REVISED JANUARY 2011 www.ti.com
Serial Data Output (SDOx)
Pin M0 sets either manual or automatic channel
selection. In manual mode, the SDI register bits
Converted data on the SDOx pins become valid with
C[1:0] are used to select between channels CHx0
the third falling CLOCK edge after generating an RD
and CHx1; in automatic operation, the SDI register
pulse. The following sections explain the different
bits C[1:0] are ignored and channel selection is
modes of operation in detail.
controlled by the device after each conversion. Pin
The digital output code format of the ADS7863 is M1 selects between serial data being transmitted
binary twos complement, as shown in Table 9. simultaneously on both outputs SDOA and SDOB for
Conversion results can be read out multiple times each channel respectively, or using only the SDOA
until a new conversion is issued from the CONVST output for transmitting data from both channels (see
input. Figure 32 through Figure 39 and the associated text
for more information).
Timing and Control
Table 8. M0/M1 Truth Table
IMPORTANT:
CHANNEL
Consider the Detailed Timing Diagram (Figure 1)
M0 M1 SELECTION SDOx USED
and CONVST timing diagram (Figure 2) shown in
0 0 Manual (via SDI) SDOA and SDOB
the Timing Characteristics section. For maximum
0 1 Manual (via SDI) SDOA only
data throughput, the descriptions and diagrams
given in this data sheet assume that the
1 0 Automatic SDOA and SDOB
CONVST and RD pins are tied together. Note
1 1 Automatic SDOA only
that they can also be controlled independently.
Additionally, the SDI pin is used for controlling device
The operation of the ADS7863 can be configured in
functionality; see the Serial Data Input section for
four different modes by using the mode pins M0 and
details.
M1, as shown in Table 8.
Table 9. ADS7863 Output Data Format
DIFFERENTIAL INPUT VOLTAGE INPUT VOLTAGE AT CHXX+ HEXADECIMAL
DESCRIPTION (CHXX+) – (CHXX–) (CHXX– = V
REF
= 2.5V) BINARY CODE CODE
Positive full-scale V
REF
5V 0111 1111 1111 7FF
Mid-scale 0V 2.5V 0000 0000 0000 000
Mid-scale – 1LSB –V
REF
/4096 2.49878V 1111 1111 1111 FFF
Negative
–V
REF
0V 1000 0000 0000 800
full-scale
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