IL41050

6

NVE Corporation

11409 Valley View Road

Eden Prairie, MN 55344-3617 USA

Telephone: (952) 829-9217

Fax (952) 829-9189

Internet: www.isoloop.com

Application Information

Power Supply Decoupling

Dominant Mode Time-out and Failsafe Receiver Functions

CAN bus latch up is prevented by an integrated Dominant mode timeout function. If the TxD pin is forced permanently low by hardware or

software application failure, the time-out returns the RxD output to the high state no more than 765 μs after TxD is asserted dominant. The timer

is triggered by a negative edge on TxD. If the duration of the low is longer than the internal timer value, the transmitter is disabled, driving the

bus to the recessive state. The timer is reset by a positive edge on pin TxD.

If power is lost on Vdd2, the IL41050 asserts the RxD output high when the supply voltage falls below 3.8 V. RxD will return to normal

operation as soon as Vdd2 rises above approximately 4.2 V.

The Isolation Advantage

Battery fire caused by over or under charging of individual lithium ion cells is a major concern in multi-cell high voltage electric and hybrid

vehicle batteries. To combat this, each cell is monitored for current flow, cell voltage, and in some advanced batteries, magnetic susceptibility.

The IL41050 allows seamless connection of the monitoring electronics of every cell to a common CAN bus by electrically isolating inputs from

outputs, effectively isolating each cell from all other cells. Cell status is then monitored via the CAN controller in the Battery Management

System (BMS).

Another major advantage of isolation is the tremendous increase in noise immunity it affords the CAN node, even if the power source is a

battery. Inductive drives and inverters can produce transient swings in excess of 20 kV/μs. The traditional, non-isolated CAN node provides some

protection due to differential signaling and symmetrical driver/receiver pairs, but the IL41050 typically provides more than twice the dV/dt

protection of a traditional CAN node.

TxD

RxD

CANL

Tx0

Rx0

ADR 0...7, CS

XTAL1

XTAL2

SJA1000

CANH

IL41050

Fig. 2. Isolated CAN node using the IL41050 and an SJA1000 MCU.

Programmable Power-Up

A unique non-volatile programmable power-up feature prevents unstable nodes. A state that needs to be present at node power up can be

programmed at the last power down. For example if a CAN node is required to “pulse” dominant at power up, TxD can be sent low by the

controller immediately prior to power down. When power is resumed, the node will immediately go dominant allowing self-check code in the

microcontroller to verify node operation. If desired, the node can also power up silently by presetting the TxD line high at power down. At the

next power on, the IL41050 will remain silent, awaiting a dominant state from the bus.

The microcontroller can check that the CAN node powered down correctly before applying power at the next “power on” request. If the node

powered down as intended, RxD will be set high and stored in IL41050’s non-volatile memory. The level stored in the RxD bit can be read

before isolated node power is enabled, avoiding possible CAN bus disruption due to an unstable node.