Datasheet

LTC2497
18
2497fa
GLOBAL ADDRESS
SCL
SDA
LTC2497 LTC2497 LTC2497…
ALL LTC2497s IN SLEEP CONVERSION OF ALL LTC2497s
DATA INPUT
S W ACK WRITE (OPTIONAL) P
2497 F08
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 LTC2497s with a Global
Address Call
In applications where several LTC2497s (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
Figure 8. Synchronize Multiple LTC2497s with a Global Address Call
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
without changing the channel, a Stop may be issued after
acknowledgement of the global write command. Global
read commands are not allowed and the converters will
NAK a global read request.
Driving the Input and Reference
The input and reference pins of the LTC2497 are connected
directly to a switched capacitor network. Depending on
the relationship between the differential input voltage and
the differential reference voltage, these capacitors are
switched between these four pins. Each time a capacitor
is switched between two of these pins, a small amount
applicaTions inForMaTion