IC-DI Datasheet, PDF (10/15 Pages) IC-Haus GmbH – DUAL SENSOR INTERFACE

iC-DI
DUAL SENSOR INTERFACE
DESCRIPTION OF FUNCTIONS
Rev C2, Page 10/15
Overload detection
To protect the device against excessive power dissipa-
tion due to high currents the switches are clocked if an
overload occurs. If a short circuit is detected, i.e. if the
voltage at the switch output overshoots or undershoots
Overload Detection Threshold off (cf. Electrical Char-
acteristics Nos. 104 and 204), the switches are shut
down for a typical 50 ms (cf. Electrical Characteristics
No. 302) and the current flow thus interrupted.
VBR
NUVD
NOVL
OEN
Qyx
tuvcl
toldly
tolcl
Figure 1: Permanent short circuit
The level of power dissipation is dependent on the
current and the time during which this current flows.
A current which fails to trigger the overload detec-
tion is not critical; high current can also be tolerated
for a short period and with low repeat rates. This is
particularly important when switching capacitive loads
(charge/discharge currents).
tion. This integrator is an 8-bit counter which is up-
dated together with the oscillator clock. If an overload
is detected on one channel the counter is raised by 1;
an overload on both channels increases the counter
value by 2. If no overload is apparent the counter is
reduced by 1 every 10 clock pulses. Provided that the
time during which excessive current flows does not ex-
ceed the value stipulated by Electrical Characteristics
No. 301, a maximum duty cycle – without deactiva-
tion of the switches – of 1:10 results if one channel
is overloaded; if both channels signal an overload this
changes to 1:5. Only when these ratios are exceeded
can the counter achieve its maximum value, this then
generating an error message at NOVL and deactivat-
ing the switches.
Configuring the switches
The various functions of the switches are determined
by pins QCFG1 and QCFG2. A voltage at the QCFG
pins which is lower than Va()lo deactivates the relevant
high-side switches; with a voltage higher than Va()hi
the relevant low-side switches are deactivated. Both
high-side and low-side switches are activated in the
open-circuit voltage range (pin open).
Valo()hys
QPx active
VBR
NUVD
NOVL
OEN
INx
Qyx
Off
Integrator
tuvcl
QNx active
Vahi()hys
Valo()
Vahi() _V(QCNFx)
Figure 3: Levels at QCFG1/QCFG2 and switch activa-
tolcl
tion
Figure 2: Overload
So that this is possible a shared back-end integrator
follows the switches for the purpose of overload detec-
Pull-up and pull-down currents
The pull-down currents at pins IN1, IN2, INV1 and
CFP are two-stage with switching thresholds Vt()hi and
Vt()lo (cf. Electrical Characteristics Nos. 604 and 815).