ADM3053BRWZ-REEL7 AD [Analog Devices], ADM3053BRWZ-REEL7 Datasheet - Page 13

• Manufacturer Part Number: ADM3053BRWZ-REEL7
• Description: Signal and Power Isolated CAN Transceiver with Integrated Isolated DC-to-DC Converter
• Manufacturer: AD [Analog Devices]

CIRCUIT DESCRIPTION
CAN TRANSCEIVER OPERATION
A CAN bus has two states called 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 impedance state.
Pin 18 (R
selected: high-speed and slope control. For high-speed
operation, the transmitter output transistors are simply
switched on and off as fast as possible. In this mode, no
measures are taken to limit the rise and fall slopes. A shielded
cable is recommended to avoid EMI problems. High-speed
mode is selected by connecting Pin 18 to ground.
Slope control mode allows the use of an unshielded twisted pair
or a parallel pair of wires as bus lines. To reduce EMI, the rise
and fall slopes should be limited. The rise and fall slopes can be
programmed with a resistor connected from Pin 18 to ground.
The slope is proportional to the current output at Pin 18.
SIGNAL ISOLATION
The ADM3053 signal isolation is implemented on the logic side of
the interface. The part achieves signal isolation by having a
digital isolation section and a transceiver section (see Figure 1).
Data applied to the TxD pin referenced to logic ground (GND1)
are coupled across an isolation barrier to appear at the transceiver
section referenced to isolated ground (GND2). Similarly, the
single-ended receiver output signal, referenced to isolated
ground in the transceiver section, is coupled across the isolation
barrier to appear at the RxD pin referenced to logic ground
(GND1). The signal isolation is powered by the V
allows the digital interface to 3.3 V or 5 V logic.
POWER ISOLATION
The ADM3053 power isolation is implemented using an
isoPower integrated isolated dc-to-dc converter. The dc-to-dc
converter section of the ADM3053 works on principles that are
common to most modern power supplies. It is a secondary side
controller architecture with isolated pulse-width modulation
(PWM) feedback. V
that switches current into a chip-scale air core transformer.
Power transferred to the secondary side is rectified and regulated to
5 V. The secondary (V
creating a PWM control signal that is sent to the primary (V
side by a dedicated iCoupler data channel. The PWM modulates
the oscillator circuit to control the power being sent to the
secondary side. Feedback allows for significantly higher power
and efficiency.
S
) allows two different modes of operation to be
CC
ISO
power is supplied to an oscillating circuit
) side controller regulates the output by
IO
pin and
CC
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TRUTH TABLES
The truth tables in this section use the abbreviations found in
Table 9.
Table 9. Truth Table Abbreviations
Letter
H
L
X
Z
I
NC
Table 10. Transmitting
V
On
On
On
Off
On
Table 11. Receiving
Supply Status
V
On
On
On
On
Off
On
1
THERMAL SHUTDOWN
The ADM3053 contains thermal shutdown circuitry that protects
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 die temperature of 150°C is reached.
As the device cools, the drivers are reenabled at a temperature of
140°C.
DC CORRECTNESS AND MAGNETIC FIELD IMMUNITY
The digital signals transmit across the isolation barrier using
iCoupler technology. This technique uses chip-scale transformer
windings to couple the digital signals magnetically from one
side of the barrier to the other. Digital inputs are encoded into
waveforms that are capable of exciting the primary transformer
Supply Status
X = don’t care.
IO
IO
V
On
On
On
On
Off
V
On
On
On
On
On
Off
CC
CC
Input
TxD
L
H
Floating
X
L
V
≥ 0.9 V
≤ 0.5 V
0.5 V < V
Inputs open
X
X
1
1
ID
Description
High level
Low level
Don’t care
High impedance (off )
Indeterminate
Not connected
= CANH − CANL
ID
< 0.9 V
Bus State
Dominant
Recessive
Recessive
Recessive
Indeterminate
Inputs
Outputs
Bus State
Dominant
Recessive
X
Recessive
X
X
1
1
1
CANH
H
Z
Z
Z
I
ADM3053
Output
RxD
L
H
I
H
I
H
CANL
L
Z
Z
Z
I