IC-RC1000_14 Datasheet, PDF (8/14 Pages) IC-Haus GmbH – SIN/COS SIGNAL SAFETY MONITOR IC

iC-RC1000
SIN/COS SIGNAL SAFETY MONITOR IC
APPLICATION NOTES
Rev C2, Page 8/14
Application with Series Resistors
The input pins can be loaded permanently with up to 2 mA, and this permissible maximum current determines
the resistor value of Rv. The input pins are limited to the supply voltage plus the clamp voltage Vc()hi by the
integrated clamping circuit (see Elec.Char. No. 002).
VCC1
VCC2
PSIN
NSIN
PCOS
NCOS
Rv
VCC1 VCC2
PSIN
Rv
NSIN
OK
Rv
iC-RC1000
PCOS
ERR
Rv
NCOS
GND
GND
Figure 3: Overvoltage protection with external resistors
OK
ERR
GND
In this application, the following must be paid attention to:
1. The power loss in the series resistor
2. The cut-off frequency at the input pins
The following example refers to the measurings with the evaluation board RC1D. For an overvoltage capability
of up to 36 V resistors of for instance 39 kΩ or 18 kΩ can be used. On the evaluation board the capacity of each
input pin is approximately 10 pF. The cut-off frequency can be calculated using the capacity and the selected
series resistor (Table 4).
39 kΩ
18 kΩ
408 kHz
880 kHz
Table 4: Cut-off frequency (-3 dB) with series resistor
A -3 dB cut-off frequency of 880 kHz means that the input amplitude at 500 kHz is already approximately 1 dB
lower. Concerning the amplitude monitoring this means that the error message at 500 kHz is only carried out at
a 10 % higher input amplitude.
Note: The iC’s pin capacity is approximately 5 pF; additional capacitances should be kept as low as possible if
higher frequency input signals are to be monitored.