Datasheet

LTC2309
19
2309fd
AppLICAtIOns InFORMAtIOn
Acquisition
The LTC2309 begins acquiring the input signal at dif-
ferent instances depending on whether a read or write
operation is being performed. If a read operation is
being performed, acquisition of the input signal begins
on the rising edge of the 9th clock pulse following the
address frame, as shown in Figure 13a.
If a write operation is being performed, acquisition of
the input signal begins on the falling edge of the sixth
clock cycle after the D
IN
word has been shifted in, as
shown in Figure 13b. The LTC2309 will acquire the
signal from the input channel that was most recently
programmed by the D
IN
word. A minimum of 240ns is
required to acquire the input signal before initiating a
new conversion.
1 2
A6SDA
SCL
A5 A4 A3 A2 A1 A0 R/W
3 4 5 6 7 8 9 1 2
B11
ACQUISITION BEGINS
t
ACQ
2309 F13a
B10
1 2
A2 A1 A0 R/WSDA
SCL
S/D O/S S1 S0 UNI X X
3 4 55 6 7 8 9 6 7 8 9
ACQUISITION BEGINS
t
ACQ
2309 F13b
SLP
Figure 13a. Timing Diagram Showing Acquisition During a Read Operation
Figure 13b. Timing Diagram Showing Acquisition During a Write Operation
INPUT VOLTAGE (V)
0V
OUTPUT CODE (TWO’S COMPLEMENT)
–1
LSB
2309 F14
011...111
011...110
000...001
000...000
100...000
100...001
111...110
1
LSB
BIPOLAR
ZERO
111...111
FS/2 – 1LSB–FS/2
FS = 4.096V
1LSB = FS/2
12
1LSB = 1mV
INPUT VOLTAGE (V)
OUTPUT CODE
2309 F15
111...111
111...110
100...001
100...000
000...000
000...001
011...110
011...111
FS – 1LSB0V
UNIPOLAR
ZERO
FS = 4.096V
1LSB = FS/2
12
1LSB = 1mV
Figure 14. Bipolar Transfer Characteristics (2’s Complement) Figure 15. Unipolar Transfer Characteristics (Straight Binary)