TH8056KDCA MELEXIS [Melexis Microelectronic Systems], TH8056KDCA Datasheet - Page 15

• Manufacturer Part Number: TH8056KDCA
• Description: Enhanced Single Wire CAN Transceiver
• Manufacturer: MELEXIS [Melexis Microelectronic Systems]

3.9 Power Dissipation
The TH8056 has an integrated protection against thermal overload. If the junction temperature reaches the
thermal shutdown threshold the TH8056 disables the transmitter driver to reduce the power dissipation to
protect the IC itself from thermal overload. The function of the transceiver will become again available if the
junction temperate drops below the thermal recovery temperature.
To secure a stable functioning within the application and to avoid a transmitter switch off due to thermal
overload under normal operating conditions, the application must take care of the maximum power
dissipation of the IC. The junction temperature can be calculated with:
The Junction temperature shouldn’t exceed under normal operating conditions the limit specified in chapter
2.3 Static Characteristics.
The power dissipation of an IC is the major factor determining the junction temperature. The TH8056
consumes current in different functions. A part of the supply current goes to the load and the other part
dissipates internally. The internal part has a constant passive part and an active part which depends on the
actual bus transmission. The complete internal part causes and increasing of the junction temperature.
The internal passive part can be calculated with the operating voltage and the normal mode supply current
recessive. The active part can be calculated with the voltage drop of the driving transistor and the current of
the CAN bus. The active part generates only during data transmission power dissipation. Therefore the duty
cycle has to be taken into account.
The power dissipation of the load can be calculated with the CANH voltage and the CAN bus current.
where
TH8056 – Datasheet
3901008056
T
P
P
P
P
I
load
J
tot
INT_p
INT_a
load
= T
= P
= V
= V
a
= V
= (V
INT_a
+ P
CANH
T
T
P
θ
P
P
P
D
V
I
I
D
V
P
I
V
R
CANH
BAT
load
load
ja
J
a
d
INT_a
INT_p
tot
BAT
BAT
CANH
load
CANH
load_net
BAT
d
+ P
/ R
* θ
* I
* I
– V
ja
BAT
load_net
INT
load
Junction temperature
Ambient temperature
Dissipated power
Thermal resistance
Internal power dissipation active
Internal power dissipation passive
Overall power dissipation
Duty cycle for data transmission
Battery supply voltage
Normal mode supply current recessive
Can network current
Duty cycle for data transmission
Voltage at CANH pin
Power dissipation of the load resistor
Current of CAN network
Voltage at CANH pin
Network total resistance
CANH
_
* D
P
) * I
load
* D
Page 15 of 26
Enhanced Single Wire CAN Transceiver
TH8056
March 2007
Rev 012