24

When switching the outputs, for some nanoseconds both transistors at the output will be momentarily conducting,

and - as is usual with digital CMOS circuits having push-pull outputs-current peaks of several mA will be generated

on the supply line (see Figure 22.).

-1

0

1

2

3

4

5

6

7

0

15

30

45

60

75

90

105 120 135 150 165 180 195

t [ns]

-30

-25

-20

-15

-10

-5

0

5

10

15

∆ ICC

CONTROL

Figure 22.

Current peaks on the supply line when switching the RESET output

To prevent these current peaks causing malfunction of the circuit, a blocking capacitor having a value of 0.1

µF

should be connected between the supply line and Ground. This will ensure that the switching currents which arise do

not generate unacceptable disturbances on the supply line.

When laying out the circuit board for a monitoring circuit, care must be taken that no currents resulting from other

nearby circuits can flow in the lines leading to the monitor section. An additional critical point in the layout is the

this is the use of a star-shaped connection of all connections to Ground, which will reduce undesirable coupling to a

minimum.

avoid the above mentioned undesirable influences.