TH8080 Datasheet, PDF (14/23 Pages) Melexis Microelectronic Systems – SoloLIN Transceiver

TH8080
SoloLIN Transceiver
5.2 Slope time calculation
V_BUS
100%
60%
60%
40%
40%
0%
V_dom
t_sdom
t_srec
Figure 7 - Slope time and slew rate calculation in accordance to LIN 1.3
The slew rate of the bus voltage is measured between 40% and 60% of the output voltage swing (linear
region). The output voltage swing is the difference between dominant and recessive bus voltage.
dV/dt = 0.2*V_swing / (t_40% - t_60% )
The slope time is the extension of the slew rate tangent until the upper and lower voltage swing limits:
t_slope = 5 * (t_40% - t_60% )
The slope time of the recessive to dominant edge is directly determined by the slew rate control of the
transmitter:
t_slope = V_swing / dV/dt
The dominant to recessive edge is influenced from the network time constant and the slew rate control,
because it’s a passive edge. In case of low battery voltages and high bus loads the rising edge is only
determined by the network. If the rising edge slew rate exceeds the value of the dominant one, the slew rate
control determines the rising edge.
TH8080 – Datasheet
3901008080
Page 14 of 23
July 2004
Rev 006