LTC2488 LINER [Linear Technology], LTC2488 Datasheet - Page 13

• Manufacturer Part Number: LTC2488
• Description: 16-Bit 2-/4-Channel ?? ADC with Easy Drive Input Current Cancellation
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
Data is shifted out of the SDO pin under control of the
serial clock (SCK) (see Figure 3). Whenever ⎯ C ⎯ S is HIGH,
SDO remains high impedance and SCK is ignored.
In order to shift the conversion result out of the device,
⎯ C ⎯ S must fi rst be driven LOW. ⎯ E ⎯ O ⎯ C is seen at the SDO pin
of the device once ⎯ C ⎯ S is pulled LOW. ⎯ E ⎯ O ⎯ C changes in real
time as a function of the internal oscillator or the clock
applied to the f
of a conversion. This signal may be used as an interrupt for
an external microcontroller. Bit 23 ( ⎯ E ⎯ O ⎯ C ) can be captured
on the fi rst rising edge of SCK. Bit 22 is shifted out of the
device on the fi rst falling edge of SCK. The fi nal data bit
(Bit 0) is shifted out on the on the falling edge of the 23rd
SCK and may be latched on the rising edge of the 24th SCK
pulse. On the falling edge of the 24th SCK pulse, SDO goes
HIGH indicating the initiation of a new conversion cycle.
(EXTERNAL)
Table 2. Output Data Format
Differential Input Voltage
V
V
0.5 • V
0.25 • V
0.25 • V
0
–1LSB
–0.25 • V
–0.25 • V
–0.5 • V
V
*The differential input voltage V
IN
IN
IN
*
* ≥ 0.5 • V
* < –0.5 • V
SDO
SCK
SDI
REF
CS
REF
REF
REF
CONVERSION
REF
REF
** – 1LSB
**
** – 1LSB
**
DON'T CARE
**
** – 1LSB
REF
REF
**
**
O
pin from HIGH to LOW at the completion
IN
= IN
SLEEP
+
– IN
–
BIT 23
. **The differential reference voltage V
1
EOC
1
BIT 22
“0”
0
2
Bit 23
⎯ E ⎯ O ⎯ C
0
0
0
0
0
0
0
0
0
0
BIT 21
Figure 3. Channel Selection and Data Output Timing
SIG
EN
3
BIT 20 BIT 19 BIT 18 BIT 17 BIT 16 BIT 15 BIT 14 BIT 13 BIT 12 BIT 11
MSB
SGL
Bit 22
DMY
4
0
0
0
0
0
0
0
0
0
0
ODD
5
REF
Bit 21
A2
SIG
= REF
6
1
1
1
1
1
0
0
0
0
0
DATA INPUT/OUTPUT
+
A1
– REF
7
Bit 20
MSB
–
.
A0
1
0
0
0
0
1
1
1
1
0
This bit serves as ⎯ E ⎯ O ⎯ C (Bit 23) for the next conversion
cycle. Table 2 summarizes the output data format.
As long as the voltage on the IN
tween –0.3V and V
range) a conversion result is generated for any differential
input voltage V
V
conversion result is clamped to the value corresponding to
+FS + 1LSB. For differential input voltages below –FS, the
conversion result is clamped to the value –FS – 1LSB.
INPUT DATA FORMAT
The LTC2488 serial input word is 8 bits long. The input
bits (SGL, ODD, A2, A1, A0) are used to select the input
channel.
8
REF
. For differential input voltages greater than +FS, the
9
Bit 19
0
1
1
0
0
1
1
0
0
1
10
11
Bit 18
IN
0
1
0
1
0
1
0
1
0
1
CC
from –FS = –0.5 • V
12
+ 0.3V (absolute maximum operating
13
Bit 17
0
1
0
1
0
1
0
1
0
1
BIT 10
DON'T CARE
14
+
BIT 9
and IN
…
…
…
…
…
…
…
…
…
…
…
REF
–
LTC2488
pins remains be-
Bit 4
LSB
to +FS = 0.5 •
BIT 0
0
1
0
1
0
1
0
1
0
1
24
Bits 3 to 0
Always 0
13
0000
0000
0000
0000
0000
0000
0000
0000
0000
0000
2488f
2488 F03