MCP2561FD-ESLASHMF datasheet(3/32 Pages) MICROCHIP

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 2014 Microchip Technology Inc.

DS20005284A-page 3

MCP2561/2FD

1.0

DEVICE OVERVIEW

The MCP2561/2FD is a high-speed CAN device,

fault-tolerant device that serves as the interface

between a CAN protocol controller and the physical

bus. The MCP2561/2FD device provides differential

transmit and receive capability for the CAN protocol

controller, and is fully compatible with the ISO-11898-2

and ISO-11898-5 standards.

The Loop Delay Symmetry is guaranteed to support

data rates that are up to 5 Mbps for CAN FD (Flexible

Data rate). The maximum propagation delay was

improved to support longer bus length.

Typically, each node in a CAN system must have a

device to convert the digital signals generated by a

CAN controller to signals suitable for transmission over

the bus cabling (differential output). It also provides a

buffer between the CAN controller and the high-voltage

spikes that can be generated on the CAN bus by

outside sources.

1.1

Mode Control Block

The MCP2561/2FD supports two modes of operation:

• Normal Mode

• Standby Mode

These modes are summarized in Table 1-1.

1.1.1

NORMAL MODE

Normal mode is selected by applying low-level voltage

to the STBY pin. The driver block is operational and

can drive the bus pins. The slopes of the output signals

on CANH and CANL are optimized to produce minimal

electromagnetic emissions (EME).

The high speed differential receiver is active.

1.1.2

STANDBY MODE

The device may be placed in Standby mode by

applying high-level voltage to the STBY pin. In Standby

mode, the transmitter and the high-speed part of the

receiver are switched off to minimize power

consumption. The low-power receiver and the wake-up

filter blocks are enabled to monitor the bus for activity.

The receive pin (RXD) will show a delayed

representation of the CAN bus, due to the wake-up

filter.

The CAN controller gets interrupted by a negative edge

on the RXD pin (Dominant state on the CAN bus). The

CAN controller must put the MCP2561/2FD back into

Normal mode, using the STBY pin, in order to enable

high speed data communication.

The CAN bus wake-up function requires both supply

voltages, VDD and VIO, to be in valid range.

1.2

Transmitter Function

The CAN bus has two states:

• Dominant State

• Recessive State

A Dominant state occurs when the differential voltage

between CANH and CANL is greater than VDIFF(D)(I).

A Recessive state occurs when the differential voltage

is less than VDIFF(R)(I). The Dominant and Recessive

states correspond to the Low and High state of the TXD

input pin, respectively. However, a Dominant state

initiated by another CAN node will override a

Recessive state on the CAN bus.

1.3

Receiver Function

In Normal mode, the RXD output pin reflects the

differential bus voltage between CANH and CANL. The

Low and High states of the RXD output pin correspond

to the Dominant and Recessive states of the CAN bus,

respectively.

1.4

Internal Protection

CANH and CANL are protected against battery

short-circuits and electrical transients that can occur on

the CAN bus. This feature prevents destruction of the

transmitter output stage during such a fault condition.

The device is further protected from excessive current

loading by thermal shutdown circuitry that disables the

output drivers when the junction temperature exceeds

a nominal limit of +175°C. All other parts of the chip

remain operational, and the chip temperature is

lowered due to the decreased power dissipation in the

transmitter outputs. This protection is essential to

protect against bus line short-circuit-induced damage.

TABLE 1-1:

MODES OF OPERATION

Mode

STBY Pin

RXD Pin

LOW

HIGH

Normal

LOW

Bus is Dominant

Bus is Recessive

Standby

HIGH

Wake-up request is detected

No wake-up request detected

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