IC-GF Datasheet, PDF (13/26 Pages) IC-Haus GmbH – TRANSCEIVER

iC-GF
TRANSCEIVER
DESCRIPTION OF FUNCTIONS
Rev C1, Page 13/26
iC-GF has two independent switching channels which
enables digital sensors to drive peripheral elements.
They are designed to cope with high driver currents.
The switches are reverse-polarity protected, feature a
free-wheeling circuit for inductive loads and a satura-
tion voltage minimising system.
Reverse polarity protection
The pins VBO, QPx, QNx, VN and CFI on the line side
of the chip are reverse polarity protected. As far as the
maximum voltage ratings are not exceeded, no possi-
ble supply combination at the line side pins can dam-
age the chip.
I(Qx)
responds to the free-wheeling circuit activated. The
switching channels are designed so that QNx can only
sink current and QPx can only source current (no re-
verse current).
Free-wheeling circuit for inductive loads
The free-wheeling circuit is always present and does
not depend on the current output status. It is activated
by voltages higher than 36 V at QNx referenced to VN
or lower than -36 V at QPx referenced to VBO. In that
case the correspondent channel will switch on without
current limitation (see Figure 4).
I(Qx)
36V
Ipeak
Isc()lo
VN
4V
A
VBO
B
36V
V(Qx)
C
VBO-36V
VN
36V
VBO
VAR
VN+36V
V(Qx)
Figure 4: Free-wheeling characteristic
Figure 2: QNx characteristic when active
VBO-36V
C
I(Qx)
Isc()hi
VN B
Ipeak
36V
A VBO V(Qx)
Dead time
In order to avoid current flow between high- and low-
side switch in push-pull configuration, a dead time t_dead
is implemented as shown in Figure 5 (cf. Electrical
Characteristics Nos. 112 and 212).
ttrig
tdead
INx
QNx
Figure 3: QPx characteristic when active
QPx
Output characteristics of Q1, Q2
The switching channels are current limited to a value
set by the external resistor RSET (cf. Electrical Char-
acteristics No. D03). If pin ISET is short circuited to
GND, the current limitation will be set to a maximum
value (cf. Electrical Characteristics Nos. 108, 208).
The current limitation works only for voltages higher
than 4 V at QNx resp. lower than VBO − 4 V at QPx.
For smaller output voltages the current limitation is re-
duced in order to minimise the saturation voltages with-
out increasing the power dissipation. Figures 2 and
3 show the characteristic of the switching channels
when activated. Region "A" is the saturation range,
where the current limitation is not fully active yet and
region "B" is the current limited range. Region "C" cor-
Figure 5: Propagation delay
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.
The level of power dissipation depends on the cur-
rent and the time during which this current flows. A
current which fails to trigger the overload detection