TH3122 Datasheet, PDF (6/14 Pages) Melexis Microelectronic Systems – K-Bus Transceiver with integrated Voltage Regulator

TH3122
K-Bus Transceiver with integrated Voltage Regulator
Application Hints
Operating during Disturbances
The absence of V_S ,V_CC or GND connection or ground
shift either alone or in any combination, do not influence
or disturb the communication between other bus nodes.
Undervoltage
The reset unit secures the correct behavior of the driver
during undervoltage. The inputs have pull-up or pull-
down characteristics and have therefore defined voltage
levels.
With 4.5V ≤ V_CC ≤ 5.25V the bus connection operates
within the correct parameters .
If V_RES1 ≤ V_CC ≤4.5V the TxD signal is transmitted to the
bus. The receive mode is also active.
If V_CC < V_RES1the bus driver is tristate.
SENSE and SO output the correct signal if V_CC > V_RES .
The specificated values of the input voltages on SO can’t
guaranteed.
Regulator Circuitry
The choice and dimension of the capacitor on VCC is
determined by application point of view. Important
parameters are the current difference on load changes
and the maximum short time voltage drop.
The VCC pin must be connected to a min. 2 µ F
capacitor for stable operating of the regulator in the
whole operating range.
Short Circuit Proof
All in- and outputs are short circuit proof to battery and
ground. A thermal shut down circuit prevents VCC and
BUS from any damage.
Baud Rate
The TH3122 has a maximum Baud rate of 9600 Baud
(C_BUS < 25nF, R_PU > 400 Ω).
Application Circuitry
V_Bat
battery reverse diode
100u _47n
33uH
BUS
82p
optional
10
100p
TH3122
VS
VCC
EN SENSE
VTR RESET
GND _GND
GND _GND
BUS
TxD
SI
RxD
SO SEN/STA
µC
+5V
Port X.1
Reset
6.8u
TxD
RxD
Control Unit
Figure 8 - Application Circuit
There should be used an LC-Filter to minimize the influence of EMI on the BUS lines.
3901003122
Rev 004
Page 6
Dec/04