LTC2487 Linear Technology, LTC2487 Datasheet - Page 20

• Manufacturer Part Number: LTC2487
• Description: 16-Bit 2-/4-Channel ADC
• Manufacturer: Linear Technology

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Operation Sequence
The LTC2487 acts as a transmitter or receiver, as shown
in Figure 6. The device may be programmed to perform
several functions. These include input channel selection,
measure the internal temperature, selecting the line fre-
quency rejection (50Hz, 60Hz, or simultaneous 50Hz and
60Hz), a 2x speed mode and gain.
Continuous Read
In applications where the input channel/configuration does
not need to change for each cycle, the conversion can be
continuously performed and read without a write cycle
(see Figure 7). The configuration/input channel remains
unchanged from the last value written into the device. If
the device has not been written to since power up, the
configuration is set to the default value. At the end of a
LTC2487
applicaTions inForMaTion
Table 6. Address Assignment
0
CONVERSION
S
S
FLOAT
FLOAT
FLOAT
HIGH
HIGH
HIGH
LOW
LOW
LOW
CA1
CONVERSION
7-BIT ADDRESS
7-BIT ADDRESS
SLEEP
FLOAT
FLOAT
FLOAT
R
HIGH
HIGH
HIGH
LOW
LOW
LOW
CA0
ACK
Figure 7. Consecutive Reading with the Same Input/Configuration
SLEEP
DATA INPUT
R/W
READ
ACK
ADDRESS
0010100
0010110
0010101
0100110
0110100
0100111
0010111
0100101
0100100
Figure 6. Conversion Sequence
P
DATA
ADDRESS
DATA INPUT/OUTPUT
read operation, a new conversion automatically begins.
At the conclusion of the conversion cycle, the next result
may be read using the method described above. If the
conversion cycle is not concluded and a valid address
selects the device, the LTC2487 generates a NAK signal
indicating the conversion cycle is in progress.
Continuous Read/Write
Once the conversion cycle is concluded, the LTC2487 can
be written to and then read from using the Repeated Start
(Sr) command.
Figure 8 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 command.
The following conversion will be performed using the newly
programmed data. In cases where the same speed (1x/2x
mode), rejection frequency (50Hz, 60Hz, 50Hz and 60Hz)
and gain is used but the channel is changed, a Stop or
Repeated Start may be issued after the first byte (channel
selection data) is written into the device.
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 or conversion configuration is required, this data
S
Sr
7-BIT ADDRESS
DATA TRANSFERRING
SLEEP
R
ACK
DATA OUTPUT
READ
P
CONVERSION
CONVERSION
P
2487 F06
2487fa
2487 F07