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iC-DXC3

DIGITAL SENSOR I/O DRIVER

Rev B2, Page 9/12

CIRCUIT PROTECTION

The iC-DXC3 is reverse polarity protected via internal

circuitry. As far as the maximum voltage ratings are not

exceeded, no possible supply combination at the line

side pins (VB, GND and OUT) can damage the chip.

Since the chip current consumption is relatively low,

discharging of the backup capacitor C1 can be very

slow, and injected charge through disturbances may

in general result in capacitor voltage exceeding maxi-

mum ratings, leading to malfunction or destruction of

circuitry and associated parts. Thus EMC requirements

will afford more external circuitry. Figure 7 shows the

iC-DXC3 with the additional protective device D1, D2

and D3.

3

3

4

5

6

7

8

C1

C2

1nF

36V

Low Side Switch

36V

High Side Switch

DIGITAL INPUT

VREF

REG

&

<150 C

&

iC-DXC3

FILT

8

4

5

6

7

2

1

1

100nF..

C3

1μF

EPAD

2

PSD36

D1

+

-

=1

+

++

-

D3

PSD36

OUT

3.3V

NIN

GND

VB

VOUT

OE

VRL

VRH

CFO

MON

PSD36

D2

D1

PSD36

D2

PSD36

PSD36

D3

=1

Figure 7: Circuit schematic showing protective devices

For over-voltage protection, the suppressor diodes

D1,D2 and D3 absorbs transients on supply line in-

jected externally on the cable. Clamp voltage of the

diodes should be rated slightly above maximum speci-

fied supply voltage.

These currents can be passed to ground or to VB by

the internal ESD diodes of the iC-DXC3. Whereas

negative current injection will simply be drained off to

ground, positive current injection will charge capacitor

C1 further to higher voltages. If not suppressor diodes

nor any other over-voltage protection is implemented,

the backup capacitor C1 should be kept small. A typical

100nF value is normally OK.

Suggested protective devices

voltage from 36V has to be chosen in order to minimize

the energy in iC-DXC3 for higher Voltages. For exam-

ple Diode type like Vishay GSOT36C or PJSD36W from

Panjit should be enough as protection.