L9700D-E Application information
Doc ID 022301 Rev 1 9/14
3 Application information
Figure 6. Typical application
Most integrated circuits, both HNMOS and bipolar, are very sensitive to positive and
negative overvoltages on the supply and at the inputs.
These transients occur in large numbers and with different magnitudes in the automotive
environment, making adequate protection for devices aimed at it indispensable.
Overvoltages on the supply line are faced through high voltage integration technologies or
through external protection (transil, varistor).
Signal inputs are generally protected using clamp diodes to the supply and ground, and a
current limiter resistor. However, such solutions do not always completely satisfy the
protection specifications in terms of intervention speed, negative clamping and current
leakage high enough to change analog signals.
The L9700D-E device combines a high intervention speed with a high precision positive and
negative clamp and a low current leakage providing the optimal solution to the problems of
the automotive environment.
The high intervention speed, due to the pre-bias of the limiter stage and internal feedback,
limits the voltage overshoot and avoid the use of external capacitors for the limitation of the
transient rise times.
Figure 6
illustrates a typical automotive application scheme. The resistor R
S
limits the input
current of the device and is therefore dimensioned considering the characteristics of the
transients to be eliminated.
Consequently:
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R
S
V
transient Peak
I
IN MAX
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