iC-MFL / iC-MFLT

8-/12-FOLD FAIL-SAFE LOGIC N-FET DRIVER

Rev C1, Page 10/13

DETECTING SINGLE ERRORS

If single errors are detected, safety-relevant applica-

tions require externally connected switching transistors

to be specifically shut down. Single errors can occur

when a pin is open (due to a disconnected bonding

wire or a bad solder connection, for example) or when

two pins are short-circuited.

When two output of different logic levels are short-

circuited, the driving capability of the lowside driver will

predominate, keeping the connected N-channel FETs

in a safe shutdown state.

With open pins VCC, GND or GNDR iC-MFL switches

the output stages to a safe, predefined low state via

pull-down resistors or pull-down current sources at the

inputs, subsequently shutting down any externally con-

nected N-channel FETs.

[

µA]

I(OUTx)

V(OUTx)

150

[V]

1

2

3

4

5

−30k

Ω

Figure 5: Output characteristic at OUTx with discon-

nected VCC supply

Loss of VCC potential

If the supply voltage is disconnected from VCC pin, the

outputs are tied to GNDR via internal pull-down resis-

tors of typically 30 kΩ which form a passive path from

the gate of an external switching transistor to ground.

A further increase of output current may occur due to

self-supply effects via the output of the iC, as indicated

by the arrows in Figure 5.

[

µA]

I(OUTx)

V(OUTx)

150

[V]

1

2

3

4

5

−30 k

Ω

Figure 6: Output characteristic at OUTx with open

GND pin

Loss of GND potential

If ground potential is not longer applied to GND, the

output stages are shut down and the outputs tied to

GNDR via internal pull-down resistors with a typical

value of 30 kΩ.

[mA]

I(OUTx)

V(OUTx)

3.6

[V]

1

2

3

4

5

Figure 7: Output characteristic at OUTx with open

GNDR pin

Loss of GNDR potential

If ground potential is no longer applied to the GNDR-

pin, the output stage highside drivers are shut down

and the outputs actively tied to GND via the lowside

drivers.