Datasheet

LTC1992 Family
32
1992fb
APPLICATIONS INFORMATION
Figure 5. Input Signal Limitations
–
–
+
+
R
IN
INM
NODE
INP
NODE
R
IN
R
FB
V
OCM
V
OCM
A. CALCULATE V
INCM
MINIMUM AND MAXIMUM GIVEN R
IN
, R
FB
AND V
OCM
V
INCM(MAX)
= (+V
S
– 1.3V) + (+V
S
– 1.3V – V
OCM
)
V
INCM(MIN)
= (–V
S
– 0.1V) + (–V
S
– 0.1V – V
OCM
)
B. WITH A KNOWN V
INCM
, R
IN
, R
FB
AND V
OCM
, CALCULATE COMMON MODE
VOLTAGE AT INP AND INM NODES (V
INCM(AMP)
) AND CHECK THAT IT IS
WITHIN THE SPECIFIED LIMITS.
V
INCM(AMP)
= = V
INCM
+ V
OCM
R
FB
B
B
–B
–B
–V
IN
–A
–A
V
INCM
V
OUTCM
V
INDIFF
4AV
P-PDIFF
A
A
+V
IN
2AV
P-P
2AV
P-P
2BV
P-P
2BV
P-P
–V
OUT
+V
OUT
LTC1992
V
OUTDIFF
4BV
P-PDIFF
1
G
1
G
4
G
4
G
V
INP
+ V
INM
2
G
G + 1
1
G + 1
Differential Input Signals
–
–
+
+
1992 F05
R
IN
INM
NODE
INP
NODE
R
IN
R
FB
V
OCM
V
OCM
R
FB
B
B
–B
–B
V
INREF
–A
V
OUTCM
V
REF
A
V
INSIG
2AV
P-P
2BV
P-P
2BV
P-P
–V
OUT
+V
OUT
LTC1992
V
OUTDIFF
4BV
P-PDIFF
Single-Ended Input Signals
INPUT COMMON MODE LIMITS
OUTPUT SIGNAL CLIPPING LIMIT
INPUT COMMON MODE LIMITS (NOTE: FOR THE FIXED GAIN LTC1992-X PARTS, V
INREF
AND V
INSIG
CANNOT EXCEED THE SUPPLIES)
OUTPUT SIGNAL CLIPPING LIMIT
OR
OR
V
INDIFF(MAX)
(V
P-PDIFF
) = THE LESSER VALUE OF (+V
S
– V
OCM
) OR (V
OCM
– –V
S
)
V
INREF
2
1
G
V
INSIG(MAX)
= 2
V
INSIG(MAX)
= THE LESSER VALUE OF V
INREF
+ (+V
S
– V
OCM
) OR V
INREF
+ (V
OCM
– –V
S
)
+V
S
– 1.3V – +V
S
– 1.3V – V
OCM
+
(())
V
INREF
2
1
G
V
INSIG(MIN)
= 2 –V
S
– 0.1V – –V
S
– 0.1V – V
OCM
+
(())
1
G
2
G
2
G
V
INSIG(MIN)
= THE GREATER VALUE OF V
INREF
+ (–V
S
– V
OCM
) OR V
INREF
+ (V
OCM
– +V
S
)
2
G
2
G
V
INSIGP-P
= 2 (+V
S
– –V
S
) – 1.2V (+V
S
– –V
S
) – 1.2V+
(())
R
FB
R
IN
G =
R
FB
R
IN
G =