Datasheet

LTC2489
15
2489fa
Figure 6. Write, Read, Start Conversion
Figure 7. Start a New Conversion Without Reading Old Conversion Result
APPLICATIONS INFORMATION
Figure 6 shows a cycle which begins with a data Write,
a repeated Start, followed by a Read and concluded with
a Stop command. The following conversion begins after
all 24 bits are read out of the device or after a Stop com-
mand. The following conversion will be performed using
the newly programmed data.
Discarding a Conversion Result and Initiating a New
Conversion with Optional Write
At the conclusion of a conversion cycle, a write cycle
can be initiated. Once the write cycle is acknowledged, a
Stop command will start a new conversion. If a new input
channel is required, this data can be written into the device
and a Stop command will initiate the next conversion (see
Figure 7).
Synchronizing Multiple LTC2489s with a Global
Address Call
In applications where several LTC2489s (or other I
2
C
delta-sigma ADCs from Linear Technology Corporation)
are used on the same I
2
C bus, all converters can be syn-
chronized through the use of a global address call. Prior
to issuing the global address call, all converters must have
completed a conversion cycle. The master then issues a
Start, followed by the global address 1110111, and a write
request. All converters will be selected and acknowledge
the request. The master then sends a write byte (optional)
followed by the Stop command. This will update the chan-
nel selection (optional) and simultaneously initiate a start
of conversion for all delta-sigma ADCs on the bus (see
Figure 8). In order to synchronize multiple converters
Figure 8. Synchronize Multiple LTC2489s with a Global Address Call
7-BIT ADDRESS 7-BIT ADDRESSS RW ACK ACKWRITE Sr PREAD
2489 F06
CONVERSION CONVERSIONADDRESSSLEEP DATA OUTPUTDATA INPUT
7-BIT ADDRESSS W ACK WRITE (OPTIONAL) P
2489 F07
CONVERSION CONVERSIONSLEEP DATA INPUT
GLOBAL ADDRESS
SCL
SDA
S W ACK WRITE (OPTIONAL) P
2489 F08
…LTC2489 LTC2489 LTC2489
ALL LTC2489s IN SLEEP CONVERSION OF ALL LTC2489s
DATA INPUT