L9704D datasheet(5/8 Pages) STMICROELECTRONICS

5 / 8 page

The internal clamping diodes at the contact monitor-

ing inputs, together with the external contact series

resistors RIN, allows the device to withstand tran-

sients at the contact connection. The contact series

resistor RIN limits the input current at the transient.

The dynamic behaviour of the circuit is defined by

the times tdo and tdTS. When the contact becomes

open, the input capacitor CIN must be charged

through the resistor RIN. In this case the total delay

time may also be influenced by the time constant RIN

CIN. The delay time tdTS, when disabling the device

is defined only by the internal circuitry. In bothcases,

an externaloutput capacitanceless than 50pF is as-

sumed, the internal output capacitances of the

three-state buffers are less than 5pF.

Figure 2 : The Contact Sense Input Connection with the Contact Equivalent Circuit.

Figure 3 : The Output Voltage as a Function of the Input Resistance at the Corresponding Contact Sense

Input.

L9704

5/8

L9704D Datasheet(PDF) 5 Page - STMicroelectronics