LTC1418IG View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1418IG' PDF : 30 Pages View PDF
LTC1418
APPLICATIONS INFORMATION
UNIPOLAR/BIPOLAR OPERATION AND ADJUSTMENT
Figure 9a shows the ideal input/output characteristics for
the LTC1418. The code transitions occur midway between
successive integer LSB values (i.e., 0.5LSB, 1.5LSB,
2.5LSB, … FS – 1.5LSB). The output code is natural
binary with 1LSB = FS/16384 = 4.096V/16384 = 250µV.
Figure 9b shows the input/output transfer characteristics
for the bipolar mode in two’s complement format.
Unipolar Offset and Full-Scale Error Adjustment
In applications where absolute accuracy is important,
offset and full-scale errors can be adjusted to zero. Offset
error must be adjusted before full-scale error. Figures
10a and 10b show the extra components required for
full-scale error adjustment. Zero offset is achieved by
adjusting the offset applied to the AIN– input. For zero
offset error apply 125µV (i.e., 0.5LSB) at the input and
adjust the offset at the AIN– input until the output code
flickers between 0000 0000 0000 00 and 0000 0000
0000 01. For full-scale adjustment, an input voltage of
4.095625V (FS – 1.5LSBs) is applied to AIN+ and R2 is
adjusted until the output code flickers between 1111 1111
1111 10 and 1111 1111 1111 11.
Bipolar Offset and Full-Scale Error Adjustment
Bipolar offset and full-scale errors are adjusted in a similar
fashion to the unipolar case. Again, bipolar offset error
must be adjusted before full-scale error. Bipolar offset
111...111
111...110
111...101
111...100
1LSB
=
FS
16384
=
4.096V
16384
UNIPOLAR
ZERO
000...011
000...010
000...001
000...000
0V 1
LSB
INPUT VOLTAGE (V)
FS – 1LSB
1418 F9a
Figure 9a. LTC1418 Unipolar Transfer Characteristics
ANALOG INPUT
R8
100Ω
R1
50k
R3
R4
24k
100Ω
R5 R2
47k 50k
R6
24k
10μF
0.1μF
R7
48k
5V
1 AIN+ VDD
2 AIN–
3 VREF
LTC1418
4 REFCOMP
5 AGND VSS
1418 F10a
Figure 10a. Offset and Full-Scale Adjust Circuit
If – 5V Is Not Available
011...111
011...110
000...001
000...000
111...111
111...110
BIPOLAR
ZERO
100...001
100...000
FS = 4.096V
1LSB = FS/16384
– FS/2
–1 0V 1
LSB LSB
INPUT VOLTAGE (V)
FS/2 – 1LSB
1418 F9b
Figure 9b. LTC1418 Bipolar Transfer Characteristics
–5V
R1
50k
ANALOG INPUT
R3
R4
24k
100Ω
R5 R2
47k 50k
R6
24k
10μF
0.1μF
5V
1 AIN+ VDD
2 AIN–
3 VREF
LTC1418
4 REFCOMP
5 AGND VSS
*
1418 F10b
*ONLY NEEDED IF VSS GOES
ABOVE GROUND
1N5817 –5V
Figure 10b. Offset and Full-Scale Adjust Circuit
If – 5V Is Available
1418fa
14
For more information www.linear.com/LTC1418
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