Data Sheet

ADM3053

Rev. A | Page 13 of 20

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.

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

allows the digital interface to 3.3 V or 5 V logic.

POWER ISOLATION

The ADM3053 power isolation is implemented using an

iso

Power 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

that switches current into a chip-scale air core transformer.

Power transferred to the secondary side is rectified and regulated to

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.

TRUTH TABLES

The truth tables in this section use the abbreviations found in

Table 9.

Table 9. Truth Table Abbreviations

Letter

Description

H

High level

L

Low level

X

Don’t care

Z

High impedance (off )

I

Indeterminate

NC

Not connected

Table 10. Transmitting

Supply Status

Input

Outputs

TxD

Bus State

CANH

CANL

On

On

L

Dominant

H

L

On

On

H

Recessive

Z

Z

On

On

Floating

Recessive

Z

Z

Off

On

X

Recessive

Z

Z

On

Off

L

Indeterminate

I

I

Table 11. Receiving

Supply Status

Inputs

Output

Bus State

RxD

On

On

≥ 0.9 V

Dominant

L

On

On

≤ 0.5 V

Recessive

H

On

On

X1

I

On

On

Inputs open

Recessive

H

Off

On

X1

X1

I

On

Off

X1

X1

H

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

i

Coupler 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