Figure 2 : Dynamical Input Characteristics (continued) .

2b

APPLICATION INFORMATION

Most integrated circuits, both HNMOS and bipolar,

are very sensitive to positive and negative overvol-

tages on the supply and at the inputs.

These transients occur in large numbers and with

different magnitudes in the automotive environ-

ment, making adequate protection for devices ai-

med at it indispensible.

Overvoltages on the supply line are faced through

high voltage integration technologies or through ex-

ternal protection (transil, varistor).

Signal inputsare generally protected using clampdi-

odes to the supply and ground, and a current limi-ter

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 si-

gnals.

The L9700 device combines a high intervention

speed with a high precision positive and negative

clamp and a low current leakage providing the opti-

mal solution to the problems of the automotive en-

vironment.

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 ca-

pacitors for the limitation of the transient rise times.

Figure 3 illustrates a typical automotive application

the device and is therefore dimensioned consider-

ing the characteristics of the transients to be elimi-

nated. Consequently :

puts because they present a low impedance during

the sampling period.

L9700

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