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.
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.
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
RES1
the 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.
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
battery reverse diode
TH3122
VS
VCC
EN
SENSE
VTR
RESET
GND
GND
GND
GND
BUS
TxD
SI
RxD
SO SEN/STA
µC
+5V
Port X.1
Reset
V
Bat
100u
47n
33uH
6.8u
TxD
RxD
BUS
optional
10
82p
Control Unit
100p
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
MELEXIS [ Melexis Microelectronic Systems ]
