TH8061 Datasheet, PDF (22/36 Pages) Melexis Microelectronic Systems – Voltage Regulator with integrated LIN Transceiver

TH8061
Voltage Regulator with integrated LIN Transceiver
4. Application Hints
4.1 Power Dissipation and operating range
The maximum power dissipation depends on the thermal resistance of the package and the PCB, the
temperature difference between Junction and Ambient as well as the airflow.
The power dissipation can be calculated with:
P_D = (V_SUP – V_CC) * I_VCC + P_{D_TX}
The power dissipation of the transmitter P_{D_TX} depends on the transceiver configuration and its parameters
as well as on the bus voltage V_BUS=V_BAT-V_D, the resulting termination resistance R_L, the capacitive bus load
C_L and the bit rate. Figure 22 shows the dependence of power dissipation of the transmitter as function of
V_SUP. The conditions for calculation of the power dissipation is R_L=500Ω, C_L=10nF, bit rate=20kbit and duty
cycle on TxD of 50%
50
45
40
35
30
25
20
15
10
5
0
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
V_SUP [V]
Figure 22 - Power dissipation LIN transceiver @ 20kbit
The permitted package power dissipation can be calculated:
P_Dmax
=
T_j − T_A
R_{THJ − A}
If we consider that P_{D_TX_max}= f(V_SUP) the max output current I_VCC on V_CC can be calculated:
I_VCCmax
=
T_j − T_A
R _{THJ − A}
− P_{D _ TX _ max}
@ VSUP
VSUP − VCC
TH8061 – Datasheet
3901008061
Page 22 of 36
June 2004
Rev 007