Datasheet

10
®
IVC102
The input resistance seen at pin 2 includes an additional
1.5kΩ, the on-resistance of S
1
. The total input resistance is
the sum of the switch resistance and R
IN
, or 2.5kΩ in this
example.
Slew rate limit of the internal op amp is approximately
3V/µs. For most applications, the slew rate of V
OUT
should
be limited to 1V/µs or less. The rate of change is propor-
tional to I
IN
and inversely proportional to C
INT
:
This can be important in some applications since the slew-
induced input voltage is applied to the sensor or signal
source. The slew-induced input voltage can be reduced by
increasing C
INT
, which reduces the output slew rate.
NONLINEARITY
Careful nonlinearity measurements of the IVC102 yield
typical results of approximately ±0.005% using the internal
input capacitors (C
INT
= 100pF). Nonlinearity will be de-
graded by using an external integrator capacitor with poor
voltage coefficient. Performance with the internal capacitors
is typically equal or better than the sensors it is used to
measure. Actual application circuits with sensors such as a
photodiode may have other sources of nonlinearity.
1/10T
INT
1/T
INT
10/T
INT
●●●
–20dB/decade
slope
Frequency
0
–10
–20
–30
–40
–50
Frequency Response (dB)
Corner at
f = 0.32/T
INT
–3dB at
f = 0.44/T
INT
FIGURE 5. Frequency Response of Integrating Converter.
Slew Rate =
I
IN
C
INT