LTC2487 Linear Technology, LTC2487 Datasheet - Page 16

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

www.DataSheet4U.com
LTC2487
applicaTions inForMaTion
the input channel. The second word of data (IM, FA, FB,
SPD, GS2, GS1, GS0) is used to select the frequency
rejection, speed mode (1x, 2x), temperature measure-
ment, and gain.
After power-up, the device initiates an internal reset cycle
which sets the input channel to CH0-CH1 (IN
CH1), the frequency rejection to simultaneous 50Hz/60Hz,
and 1x output rate (auto-calibration enabled), and gain = 1.
The first conversion automatically begins at power-up using
this default configuration. Once the conversion is complete,
up to two words may be written into the device.
The first three bits of the first input word consist of two
preamble bits and one enable bit. Valid settings for these
three bits are 000, 100, and 101. Other combinations
should be avoided.
If the first three bits are 000 or 100, the following data is ig-
nored (don’t care) and the previously selected input channel
and configuration remain valid for the next conversion.

SCL
SDA
SCL
SDA
START BY
MASTER
START BY
MASTER
1
ADDRESS
1
7-BIT ADDRESS
7-BIT
…
2
7
…
SLEEP
SLEEP
7
8
R
W
8
LTC2487
LTC2487
ACK BY
ACK BY
Figure 3a. Timing Diagram for Reading from the LTC2487
Figure 3b. Timing Diagram for Writing to the LTC2487
9
9
SIG
1
1
+
1
= CH0, IN
0
MSB
2
2
EN
3
…
D23
SGL ODD
–
=
4
MASTER
ACK BY
9
5
If the first three bits shifted into the device are 101, then
the next five bits select the input channel for the next
conversion cycle (see Table 3).
Table 3 Channel Selection
*Default at power up
The first input bit (SGL) following the 101 sequence de-
termines if the input selection is differential (SGL = 0) or
single-ended (SGL = 1). For SGL = 0, two adjacent channels
SGL
*0
A2
0
0
0
1
1
1
1
6
1
A1
ODD/
SIGN
7
DATA INPUT
0
0
1
1
0
0
1
1
MUX ADDRESS
LSB
DATA OUTPUT
A0
2
8
LTC2487
A2
ACK BY
0
0
0
0
0
0
0
0
9
3
A1
EN2
0
0
0
0
0
0
0
0
1
(OPTIONAL 2ND BYTE)
4
IM
A0
2
0
1
0
1
0
1
0
1
ALWAYS LOW
FA
3
5
IN
IN
IN
0
FB
+
–
+
4
CHANNEL SELECTION
SPD GS2 GS1 GS0
6
IN
IN
IN
1
5
–
+
+
6
7
IN
IN
IN
2
+
–
+
7
IN
IN
IN
8
3
8
MASTER
–
+
+
NAK BY
LTC2487
ACK BY
2487 F03b
2487 F03a
9
9
COM
IN
IN
IN
IN
2487fa
–
–
–
–