Datasheet

LTC2301/LTC2305
19
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APPLICATIONS INFORMATION
Continuous Read/Write
Once the conversion cycle is complete, the LTC2301/
LTC2305 can be written to and then read from using the
repeated START (Sr) command. Figure 9 shows a cycle
which begins with a data write, a repeated START, followed
by a read and concluded with a STOP command. After
all 16 bits are read out, a conversion may be initiated by
issuing a STOP command. The following conversion will
be performed using the newly programmed data.
Synchronizing Multiple LTC2301/LTC2305s with a
Global Address Call
In applications where several LTC2301/LTC2305s or other
I
2
C SAR ADCs from Linear Technology Corporation are
used on the same I
2
C bus, all converters can be synchro-
nized 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 1101011, and a
write request. All converters will be selected and acknowl-
edge the request. The master then sends a write byte
(optional) followed by the STOP command. This will update
the channel selection (optional) and simultaneously initi-
ate a conversion for all ADCs on the bus (see Figure 10).
In order to synchronize multiple converters without chang-
ing the channel, a STOP command may be issued after
acknowledgement of the global write command. Global
read commands are not allowed and the converters will
NACK a global read request.
Nap Mode
The ADCs enter nap mode after a conversion is complete
(t
CONV
) if the SLP bit is set to a logic 0. The supply current
decreases to 225A in nap mode between conversions,
thereby reducing the average power dissipation as the
sample rate decreases. For example, the LTC2301/LTC2305
draw an average of 300µA at a 1ksps sampling rate. The
LTC2301/LTC2305 keep only the reference (V
REF
) and
reference buffer (REFCOMP) circuitry active when in nap
mode.
Figure 9. Write, Read, START Conversion
Figure 10. Synchronize Multiple LTC2301/LTC2305s with a Global Address Call
S
CONVERSION NAP DATA INPUT ADDRESS CONVERSIONDATA
OUTPUT
W ACK WRITE7-BIT ADDRESS Sr R ACK
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READ7-BIT ADDRESS P
S
SDA
SCL
CONVERSION NAP
LTC2301/LTC2305
DATA OUTPUT CONVERSION OF ALL LTC2301/05s
W ACK WRITE (OPTIONAL)GLOBAL ADDRESS P
LTC2301/LTC2305 LTC2301/LTC2305
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