isl55210 Intersil Corporation, isl55210 Datasheet - Page 15

• Manufacturer Part Number: isl55210
• Description: Wideband, Low-power, Ultra-high Dynamic Range Differential Amplifier
• Manufacturer: Intersil Corporation

V
V
CM1
cm1
2. AC coupled, higher frequency range interstage filter design.
3. AC coupled with output side transformer. This design includes
FIGURE 34. AC COUPLED, BROADBAND RLC INTERSTAGE FILTER
FIGURE 36. AC COUPLED WITH OUTPUT SIDE TRANSFORMER
This design replaces the R
valued inductors and implements the filter just using shunt
resistors at the end of the RLC filter (here, that is just the ADC
internal differential Rin). In this case, the ADC V
to the centerpoint of the bias path inductors (very much like a
Bias-T) to provide the common mode voltage and current to
the ADC inputs. These bias inductors do limit the low
frequency end of the operation where, with 1µH values,
operation from 10MHz to 200MHz is supported using the
approach of Figure 35.
an output side transformer, very similar to ADC
characterization circuits. This approach allows a slightly lower
amplifier output swing (if N > 1 is used) and very easy 2nd
ISL55210
ISL55210
R
R
R
R
f
f
F
F
+3.3V
+3.3V
1.2V
1.2V
DESIGN
R
R
R
S
R
S
s
s
Rt
C
C
≤30
b
b
Ω
C
C
b
b
1:n
15
t
resistors in Figure 34 with large
R
v
B
L
V
L
t
R >
s
b
>
s
–
V
t
R
I
b
cm
s
R
−
R
R
s
I
t
×
cm
t
2I
R
R
R
I
I
CM
t
t
t
CM
CM
×
Icm
Icm
=
R
V
t
cm2
=
C
C
C
C
t
t
V
t
t
cm
CM
2
can be tied
IN+
IN+
IN-
IN-
ADC
ADC
V
V
CM2
cm2
or 1V
or 1V
R
ISL55210
R
= 0.535
= 0.535
in
in
C
in
C
i n
V
FIGURE 35. AC COUPLED, HIGHER FREQUENCY RLC FILTER DESIGN
CM1
4. DC coupled with ADC V
FIGURE 37. DC COUPLED WITH A COMMON V
order low pass responses to be implemented. It also provides
the I
centertap. This approach would be attractive for higher ADC
input swing targets and more aggressive noise power
bandwidth control needs.
amplifier. Here, DC to very high frequency interstage low pass
filters can be provided. Again, the R
reduce the IR drop from the V
shows up on the output of the ISL55210, to the ADC input
pins. In this case, split supplies are required to satisfy the
amplifier output and input common mode range limits
discussed earlier.
ISL55210
R
R
ISL55210
CM
F
F
+3.3V
1.2V
R
R
and V
f
f
+3.0V
-1.1V
THE ADC
V
cm
CM
bias to the ADC through the transformer
R
R
S
S
R
R
Rs
s
s
C
C
CM
≤30
b
b
Ω
and I
CM
L
L
L
L
S
Lp>>
s
S
s
CM
R
of the converter, which now
T
Ls
provided from the
S
element must be low to
R
t
L
L
P
P
Icm
Icm
I
I
CM
CM
CM
VOLTAGE FROM
C
C
C
C
t
t
t
t
March 2, 2011
IN-
IN+
IN-
ADC
IN+
ADC
V
V
CM2
cm
FN7811.0
or 1V
or 1V
= 0.535V
R
R
= 0.535
in
in
C
C
in
in