S

4

DA9171A.000

July 31, 1997

FUNCTIONS

x

Input protection

The input protection is composed of a high voltage thin film series resistor, a metal-to-metal capacitor to ground

and a Zener diode to GND. The circuit provides the ability of withstanding energy rich voltage pulses as well as

fast transient high voltage bursts without damaging the MAS9171A or devices connected to it.

The resistance of each input to ground is approx. 225 kOhms. Each input is protected against electrostatic

discharge (ESD) according to Machine Model EIAJ ED-4701 Method C-111 (+/-500 kV, 200 pF, 0 Ohms).

The device has been specially designed for high decoupling between Inputs and Power Supply or Outputs to

prevent voltage overswing when applying test pulses according to DIN40839/ISO7637.

For a given ambient temperature the maximum pulse length is limited by the maximum silicon temperature of

T=150°C.

x

Analog filter

The input protection is followed by a passive low pass filter of 2nd order with a 3 dB frequency of 150 kHz. This

filter is used to block high frequency components coupled through capacitive coupling clamps or electromagnetic

field.

x

Comparator

The output signal of the analog filter of each channel is pulse-shaped by a Schmitt-Trigger Comparator with

strong output drivers. The output stage works with non-overlapping clocks to reduce current spikes at the Supply

Pins caused by change of output level.

x

Input levels

The Ouput OUTx is “High” if the corresponding input voltage VINx > 5.5 V and “Low” if VINx < 2.75 V (typical

values).

Fig 1.: Input Channel of MAS9171A

100 K

1 K

125 K

125 K

6.8V

6.8V

9pF

4pF

to Comparator

IN 1….8