Datasheet

12
LTC2400
APPLICATIONS INFORMATION
WUU
U
Table 2. LTC2400 Output Data Format
Bit 31 Bit 30 Bit 29 Bit 28 Bit 27 Bit 26 Bit 25 Bit 24 Bit 23 … Bit 4 Bit 3-0
Input Voltage EOC DMY SIG EXR MSB LSB SUB LSBs*
V
IN
> 9/8 • V
REF
001100011...1X
9/8 • V
REF
001100011...1X
V
REF
+ 1LSB 0 0 1 1 0 0 0 0 0 ... 0 X
V
REF
001011111...1X
3/4V
REF
+ 1LSB 0 0 1 0 1 1 0 0 0 ... 0 X
3/4V
REF
001010111...1X
1/2V
REF
+ 1LSB 0 0 1 0 1 0 0 0 0 ... 0 X
1/2V
REF
001001111...1X
1/4V
REF
+ 1LSB 0 0 1 0 0 1 0 0 0 ... 0 X
1/4V
REF
001000111...1X
0
+
/0
–
0 0 1/0** 0 0 0 0 0 0 ... 0 X
–1LSB 0 0 0111 1 11...1 X
–1/8 • V
REF
000111100...0X
V
IN
< –1/8 • V
REF
000111100...0X
*The sub LSBs are valid conversion results beyond the 24-bit level that may be included in averaging or discarded without loss of resolution.
**The sign bit changes state during the 0 code.
Figure 3. Output Data Timing
out on the falling edge of the 31st SCK and may be latched
on the rising edge of the 32nd SCK pulse. On the falling
edge of the 32nd SCK pulse, SDO goes HIGH indicating a
new conversion cycle has been initiated. This bit serves as
EOC (Bit 31) for the next conversion cycle. Table 2 sum-
marizes the output data format.
As long as the voltage on the V
IN
pin is maintained within
the –0.3V to (V
CC
+ 0.3V) absolute maximum operating
range, a conversion result is generated for any input value
from –0.125 • V
REF
to 1.125 • V
REF
. For input voltages
greater than 1.125 • V
REF
, the conversion result is clamped
to the value corresponding to 1.125 • V
REF
. For input
voltages below –0.125 • V
REF
, the conversion result is
clamped to the value corresponding to –0.125 • V
REF
.
Frequency Rejection Selection (F
O
Pin Connection)
The LTC2400 internal oscillator provides better than 110dB
normal mode rejection at the line frequency and all its
harmonics for 50Hz ±2% or 60Hz ±2%. For 60Hz rejec-
tion, F
O
(Pin 8) should be connected to GND (Pin 4) while
for 50Hz rejection the F
O
pin should be connected to V
CC
(Pin␣ 1).
MSBEXTSIG“0”
1 2 3 4 5 272832
BIT 0BIT 27 BIT 4
LSB
24
BIT 28BIT 29BIT 30
SDO
SCK
CS
EOC
BIT 31
SLEEP DATA OUTPUT CONVERSION
2400 F03
Hi-Z