
LTC2435/LTC2435-1
15
24351fc
applicaTions inForMaTion
While the variation in offset with supply voltage is propor-
tional to VCC (see Figure 4), several characteristics of this
variation can be used to eliminate the effects. First, the
variation with respect to supply voltage is linear. Second,
themagnitudeoftheoffseterrordecreaseswithdecreased
supply voltage. Third, the offset error in microvolts is al-
most independent with reference and therefore the offset
in ppm is inverse proportional to reference voltage. As a
result, by tying VCC to VREF , the variation with supply can
be reduced, see Figure 6. The variation with supply is less
than 15ppm over the entire 2.7V to 5.5V supply range.
Table 2. LTC2435/LTC2435-1 Output Data Format
Differential Input Voltage
VIN*
Bit 23
EOC
Bit 22
DMY
Bit 21
SIG
Bit 20
MSB
Bit 19 Bit 18
Bit 17
…
Bit 0
VIN* ≥ 0.5 VREF**
0
1
0
…
0
0.5 VREF** – 1LSB
0
1
0
1
…
1
0.25 VREF**
0
1
0
1
0
…
0
0.25 VREF** – 1LSB
0
1
0
1
…
1
0
1
0
…
0
–1LSB
0
1
…
1
–0.25 VREF**
0
1
0
…
0
–0.25 VREF** – 1LSB
0
1
0
1
…
1
–0.5 VREF**
0
1
0
…
0
VIN* < –0.5 VREF**
0
1
…
1
*The differential input voltage VIN = IN+ – IN–.
**The differential reference voltage VREF = REF+ – REF–.
Figure 3. Output Data Timing
MSB
SIG
“0”
BIT 0
BIT 19
BIT 5
LSB
BIT 20
BIT 21
BIT 22
SDO
SCK
CS
EOC
BIT 23
SLEEP
DATA OUTPUT
CONVERSION
2435 F03
Hi-Z
Figure 4. Offset vs VCC
Figure 6. Offset vs VCC (VREF = VCC)
Figure 5. Offset vs Temperature
VCC (V)
2.5
3.0
OFFSET
ERROR
(ppm
OF
V
REF
)
3.5
4.5
4.0
5.0
5.5
2435 F04
–350
–400
–450
–500
–550
–600
–650
–700
–750
REF+ = 2.5V
REF– = GND
VIN = 0V
VINCM = GND
FO = GND
TA = 25°C
TEMPERATURE (°C)
–45 –30
0
OFFSET
ERROR
(ppm
OF
V
REF
)
–15
15 30
90
2435 F05
45 60 75
–324
–325
–326
–327
–328
–329
–330
VCC = 5V
VREF = 5V
VIN = 0V
VINCM = GND
FO = GND
VCC and VREF (V)
2.5
3.0
OFFSET
ERROR
(ppm
OF
V
REF
)
3.5
4.5
4.0
5.0
5.5
2435 F06
–300
–305
–310
–315
–320
–325
–330
–335
–340
–345
–350
REF+ = VCC
REF– = GND
VIN = 0V
VINCM = GND
FO = GND
TA = 25°C
–