TH3122 Datasheet, PDF (5/14 Pages) Melexis Microelectronic Systems – K-Bus Transceiver with integrated Voltage Regulator

TH3122
K-Bus Transceiver with integrated Voltage Regulator
VS
VCC
RESET
V_RESEIN
t_Res
V_RES1/2
t_rr
Figure 7 - Initialization
The input EN has an internal pull down resistor. If
EN=high, the internal pull down current is switched off to
minimize the quiescent current.
RESET Output
The RESET output is switched from low to high if V_S is
switched on and V_CC>V_RESEIN after the time t_RES.
If the voltage V_CC drops below V_RES1 or V_RES2 then the RESET
output is switched from high to low after the time t_rr has been
reached.
The voltage level for V_RES1 and V_RES2 and the
corresponding times t_RES can be programmed via the
analogue input VTR.
Wake up with BUS traffic
If the regulator is put in standby mode it can be woken
up with the BUS interface. Every pulse on the BUS (high
pulse or low pulse) with a pulse width of min. 45 µ s will
switch on the regulator.
After the BUS has woken up the regulator, it can only be
switched off with a high level followed by a low level on
the EN pin.
Reset Programming on VTR
With the VTR pin the reset switches off levels and delay
time can be programmed.
The voltage on VCC influences the reset function.
VTR-Mode
VTR = GND
VTR = VCC
VTR with R ≥ 50k Ω to GND
VTR with R ≥ 50k Ω to VCC
V_RES
V_RES = V_RES1 = 3.15V
V_RES = V_RES2 = 4.65V
V_RES = V_RES1 = 3.15V
V_RES = V_RES2 = 4.65V
t_Res
100ms
100ms
15ms
15ms
VTR-Programming
The voltage on VTR input is read out if the voltage at this
pin is higher than V_RESEIN . This value defines the reset
switch off voltage V_RES. With the next oscillator cycle it
switches on the pull up current source if VTR=low or the
pull down current source if VTR=high. The sources are
active for one oscillator cycle. The level changes during
this procedure on VTR, which depends on the external
pull up or pull down resistors control the reset time t_Res
Temperature Limitation
If the junction temperature 150ºC < T_j < 170ºC the over
temperature recognition will be active and the regulator
voltage and the BUS driver will be switched off. After T_j
falls below 140ºC the TH3122 will be initialized,
independently of the voltage levels on EN and BUS.
The function of the TH3122 is possible between T_Amax
and the switch off temperature, but small parameter
differences can appear.
Low Voltage Detection V_S
Low voltage on V_S is monitored on SENSE output.
If V_S has reached the level of V_S =6.8V then the SENSE
output generates low level. The normal
operating range is V_S > 7.8V and the SENSE output
generates a high level.
Universal Comparator
The TH3122 consist of a universal comparator for
general use. The positive input of this comparator is
connected to the pin SI. The input voltage range of SI is
0V...V_S. The input voltage is compared with a fixed
reference voltage at high or low level and the comparator
output SO drives a 5V digital signal.
3901003122
Rev 004
Page 5
Dec/04