IC-HF Datasheet, PDF (17/36 Pages) IC-Haus GmbH – 6-CH. ENCODER LINK, RS-422 DRIVER/RECEIVER

iC-HF
preliminary
6-CH. ENCODER LINK, RS-422 DRIVER/RECEIVER
REVERSE POLARITY PROTECTION
Rev C1, Page 17/36
iC-HF is protected against applying reverse supply volt-
age at pins VDD and GND. Connecting a power supply
with reverse polarity to an unprotected chip would per-
manently damage it.
iC-HF has a reverse polarity detection block. When a
reverse polarity connection is detected, iC-HF provides
the following protection actions:
iC-HF also provides extended reverse polarity protec-
tion through output power supply lines VDDS (VDD
switched) and GNDS (GND switched). These pins are
connected to VDD and GND through a protecting switch.
When a reverse polarity is detected at VDD/GND,
VDDS and GNDS are internally disconnected. If a
sensor is supplied by iC-HF through VDDS/GNDS lines,
the polarity protection on iC-HF will be extended to the
sensor.
• Power supply for internal blocks is disabled
• Output drivers are set to high impedance. This
includes lines Q1 to Q6, NQ1 to NQ6 and NERR
line.
VDDS can supply a maximum of 60 mA (cf. Electrical
Characteristics no. 003). The current consumption
of the sensor connected to the protected supply pins
should not exceed this value.
Figure 19 shows connection of a sensor through ex-
tended reverse polarity protection.
SENSOR
VDD
GND
VDDS
GNDS
VDD
0...-5.5V
REVERSE POLARITY PROTECTION ^GND
1 μF
ERROR MONITOR
1 μF
A
B
Z
U
V
W
NERR
X1
NX1
X2
NX2
X3
NX3
X4
X5
X6
PTC
ECM
OEN
FMSEL1
FMSEL2
NERRI
BYP
EBIS TRI
CONTROL
LOGIC
OVT
PoDo
1
RS422
HIGH Z
Q1
TRI
HIGH Z ^NQ1
Q2
HIGH Z
NQ2
Q3
HIGH Z
NQ3
Q4
HIGH Z
NQ4
Q5
HIGH Z
NQ5
Q6
HIGH Z
NQ6
BYPR
ENCODER LINK
REQUEST
DETECTION
OVT
PoDo
OVERTEMP
POWER DOWN
Q1
NQ1
NERR
iC-HF
HIGH Z
Figure 19: Extended reverse polarity protection
It is possible to connect to iC-HF a sensor that demands
more than the maximum permissible load current (cf.
Electrical Characteristics no. 003). However, connec-
tion of the sensor to iC-HF pins VDDS and GNDS
should be avoided. A load exceeding this maximum
value will prevent iC-HF to comply with electrical char-
acteristic no. 701 and no. 702. Instead, the sensor
should be supplied directly through pins VDD and GND.
Figure 20 shows an example.
If configuration in Figure 20 is implemented, it must be
noticed that iC-HF will still be protected against reverse
polarity but this will not be the case of the sensor.