ADM3054 AD [Analog Devices], ADM3054 Datasheet - Page 15

• Manufacturer Part Number: ADM3054
• Description: 5 kV rms Signal Isolated High Speed CAN Transceiver with Bus Protection
• Manufacturer: AD [Analog Devices]

Data Sheet
THEORY OF OPERATION
CAN TRANSCEIVER OPERATION
A CAN bus has two states: dominant and recessive. A dominant
state is present on the bus when the differential voltage between
CANH and CANL is greater than 0.9 V. A recessive state is present
on the bus when the differential voltage between CANH and
CANL is less than 0.5 V. During a dominant bus state, the CANH
pin is high and the CANL pin is low. During a recessive bus
state, both the CANH and CANL pins are in the high imped-
ance state.
The driver drives CANH high and CANL low (dominant state)
when a logic low is present on TxD. If a logic high is present on
TxD, the driver outputs are placed in a high impedance state
(recessive state). The driver output states are presented in Table 9.
The receiver output is low when the bus is in the dominant state
and high when the bus is in the recessive state. If the differential
voltage between CANH and CANL is between 0.5 V and 0.9 V,
the bus state is indeterminate and the receiver output can be
either high or low. The receiver output states for given inputs
are listed in Table 10.
THERMAL SHUTDOWN
The
the part from excessive power dissipation during fault conditions.
Shorting the driver outputs to a low impedance source can result
in high driver currents. The thermal sensing circuitry detects
the increase in die temperature under this condition and disables
the driver outputs. This circuitry is designed to disable the driver
outputs when a junction temperature of 150°C is reached. As
the device cools, the drivers reenable at a temperature of 140°C.
ADM3054
contains thermal shutdown circuitry that protects
Rev. 0 | Page 15 of 20
TRUTH TABLES
The truth tables in this section use the abbreviations listed
in Table 8.
Table 8. Truth Table Abbreviations
Letter
H
L
I
X
Z
NC
Table 9. Transmitting
V
On
On
On
Off
On
Table 10. Receiving
V
On
On
On
On
Off
On
Supply Status
Supply Status
DD1
DD1
V
On
On
On
On
Off
V
On
On
On
On
On
Off
DD2
DD2
Input
TxD
L
H
Floating
X
L
V
≥0.9 V
≤0.5 V
0.5 V < V
Inputs open
X
X
ID
Description
High level
Low level
Indeterminate
Don’t care
High impedance (off )
Disconnected
= CANH − CANL
ID
< 0.9 V
State
Dominant
Recessive
Recessive
Recessive
I
Inputs
Bus State
Dominant
Recessive
I
Recessive
X
X
CANH
H
Z
Z
Z
I
Outputs
CANL
L
Z
Z
Z
I
RxD
L
H
I
H
I
H
ADM3054
Outputs
V
L
L
L
L
I
H
V
L
L
L
I
H
DD2SENSE
DD2SENSE