MCP2557FD/8FD
CAN FD Transceiver with Silent Mode
Features
• Silent Mode is Useful in the Following
Applications:
- Disables transmitter in redundant systems
- Implements babbling idiot protection
- Tests connection of bus medium
- Prevents a faulty CAN controller from
disrupting all network communications
• Optimized for CAN FD at 2, 5 and 8 Mbps
Operation:
- Maximum propagation delay: 120 ns
- Loop delay symmetry: ±10%(2 Mbps)
• Meets or Exceeds Stringent Automotive Design
Requirements Including “Hardware Require-
ments for LIN, CAN and FlexRay Interfaces in
Automotive Applications”, Version 1.3, May 2012:
- Conducted emissions at 2 Mbps with
Common-Mode Choke (CMC)
- DPI at 2 Mbps with CMC
• Meets SAE J2962/2 “Communication Transceiv-
ers Qualification Requirements – CAN”
- Passes radiated emissions at 2 Mbps without
a CMC
• Meets Latest ISO/DIS-11898-2:2015
• Meets Latest SAE J2284-4 and -5 Working Drafts
• Digital Inputs of the MCP2557FD are Compatible
to 3.3V and 5V Microcontrollers. R
XD
Output
Requires a 5V Tolerant Microcontroller Input
• Functional Behavior Predictable Under all Supply
Conditions:
- Device is in Unpowered mode if V
DD
drops
below Power-on Reset (POR) level
- Device is in Unpowered mode if V
IO
drops
below POR level
Description
The MCP2557FD/8FD CAN transceiver family is
designed for high-speed CAN FD applications with up
to 8 Mbps communication speed. The maximum prop-
agation delay was improved to support longer bus
length.
The device meets automotive requirements for CAN
FD bit rates exceeding 2 Mbps, low quiescent current,
electromagnetic compatibility (EMC) and electrostatic
discharge (ESD).
Package Types
MCP2557FD
SOIC
T
XD
1
V
SS
2
V
DD
3
R
XD
4
8 S
7 CANH
6 CANL
5 NC
MCP2558FD
SOIC
T
XD
1
V
SS
2
V
DD
3
R
XD
4
8 S
7 CANH
6 CANL
5 V
IO
MCP2557FD
2x3 TDFN*
T
XD
1
V
SS
2
V
DD
3
R
XD
MCP2558FD
2x3 TDFN*
T
XD
1
V
SS
2
V
DD
3
R
XD
8
S
EP
9
7
CANH
6
CANL
5
NC
8
S
EP
9
7
CANH
6
CANL
5
V
IO
4
4
MCP2557FD
3x3 DFN*
T
XD
V
SS
V
DD
R
XD
MCP2558FD
3x3 DFN*
S
CANH
CANL
NC
T
XD
V
SS
V
DD
R
XD
1
2
3
4
EP
9
8
7
6
5
1
2
3
4
EP
9
8
7
6
5
S
CANH
CANL
V
IO
Applications
CAN 2.0 and CAN FD networks in Automotive,
Industrial, Aerospace, Medical, and Consumer
applications.
*Includes Exposed Thermal Pad (EP); see
Table 1-1.
MCP2557FD/8FD Family Members
Device
MCP2557FD
MCP2558FD
Note:
V
IO
Pin
N/A
Yes
NC
Yes
N/A
TTL I/O
Yes
N/A
V
IO
I/O
N/A
Yes
—
Internal level shifter on digital I/O pins.
Description
For ordering information, see the
Product Identification System
section.
2016 Microchip Technology Inc.
DS20005533A-page 1
MCP2557FD/8FD
Block Diagram
V
IO
V
DD
DIGITAL I/O
SUPPLY
THERMAL
PROTECTION
POR
UVLO
V
IO
T
XD
PERMANENT
DOMINANT DETECT
DRIVER
AND
SLOPE CONTROL
MODE
CONTROL
CANH
V
IO
CANL
S
V
DD
R
XD
HS_RX
CANH
CANL
V
SS
Note:
Only the MCP2558FD has the V
IO
pin. In the MCP2557FD, the supply for the digital I/O is internally
connected to V
DD
.
DS20005533A-page 2
2016 Microchip Technology Inc.
MCP2557FD/8FD
1.0
DEVICE OVERVIEW
1.4
Permanent Dominant Detection
The MCP2557FD/8FD CAN transceiver family is
designed for high-speed CAN FD applications with up
to 8 Mbps communication speed. The product offers a
Silent mode controlled by the Silent mode pin. The
Silent mode is used to disable the CAN transmitter.
This ensures that the device doesn’t drive the CAN
bus. The MCP2557FD/8FD device provides
differential transmit and receive capability for the CAN
protocol controller, and is fully compatible with
specification ISO/DIS-11898-2:2015.
The loop delay symmetry is tested to support data rates
that are up to 8 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 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.
The MCP2557FD/8FD device prevents a permanent
dominant condition on T
XD
.
In Normal mode, if the MCP2557FD/8FD detects an
extended Low state on the T
XD
input, it will disable the
CANH and CANL output drivers in order to prevent
data corruption on the CAN bus. The drivers will remain
disabled until T
XD
goes High. The high-speed receiver
is active, and data on the CAN bus is received on R
XD
.
The condition has a time-out of 1.9 ms (typical). This
implies a maximum bit time of 128 µs (7.8 kHz),
allowing up to 18 consecutive dominant bits on the bus.
1.5
Power-on Reset (POR) and
Undervoltage Detection
The MCP2557FD/8FD have POR detection on both
supply pins, V
DD
and V
IO
. Typical POR thresholds to
deassert the reset are 1.2V and 3.0V for V
IO
and V
DD
,
respectively.
When the device is powered on, CANH and CANL
remain in a high-impedance state until V
DD
exceeds its
undervoltage level. Once powered on, CANH and
CANL will enter a high-impedance state if the voltage
level at V
DD
drops below the undervoltage level,
providing voltage brown-out protection during normal
operation.
The receiver output is forced to a Recessive state
during an undervoltage condition on V
DD
.
1.1
Transmitter Function
The CAN bus has two states: Dominant and
Recessive. A Dominant state occurs when the
differential voltage between CANH and CANL is
greater than V
DIFF
(
D
)(
I
). A Recessive state occurs
when the differential voltage is less than V
DIFF
(
R
)(
I
).
The Dominant and Recessive states correspond to the
Low and High states of the T
XD
input pin, respectively.
However, a Dominant state initiated by another CAN
node will override a Recessive state on the CAN bus.
1.2
Receiver Function
The R
XD
output pin reflects the differential bus voltage
between CANH and CANL. The Low and High states of
the R
XD
output pin correspond to the Dominant and
Recessive states of the CAN bus, respectively.
1.3
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 guard against bus line short-
circuit-induced damage. Thermal protection is only
active during Normal mode.
2016 Microchip Technology Inc.
DS20005533A-page 3
MCP2557FD/8FD
1.6
Mode Control
Figure 1-1
shows the state diagram of the MCP2557FD/
8FD.
1.6.1
UNPOWERED MODE (POR)
The MCP2557FD/8FD enters Unpowered mode if any
of the following conditions occur:
• After powering up the device
• If V
DD
drops below V
PORL
• If V
IO
drops below V
PORL
_V
IO
In Unpowered mode, the CAN bus will be biased to
ground using a high impedance. The MCP2557FD/
8FD is not able to communicate on the bus.
1.6.2
WAKE MODE
The MCP2557FD/8FD transitions from Unpowered
mode to Wake mode when V
DD
and V
IO
are above
their PORH levels. From Normal mode, if V
DD
is
smaller than V
UVL
, or if the bandgap output voltage is
not within valid range, the device will also enter Wake
mode.
In Wake mode, the CAN bus is biased to ground and
R
XD
is always high.
1.6.3
NORMAL MODE
When V
DD
exceeds V
UVH
, the band gap is within valid
range and T
XD
is High, the device transitions into
Normal mode. During POR, when the microcontroller
powers up, the T
XD
pin could be unintentionally pulled
down by the microcontroller powering up. To avoid
driving the bus during a POR of the microcontroller,
the transceiver proceeds to Normal mode only after
T
XD
is high.
In Normal mode, the driver block is operational and
can drive the bus pins. The slopes of the output
signals on CANH and CANL are optimized to reduce
Electromagnetic Emissions (EME). The CAN bus is
biased to V
DD
/2.
The high-speed differential receiver is active.
1.6.4
SILENT MODE
The device may be placed in Silent mode by applying
a high level to the ‘S’ pin (pin 8). In Silent mode, the
transmitter is disabled and the CAN bus is biased to
V
DD
/2. The high-speed differential receiver is active.
The CAN controller must put the MCP2557FD/8FD
back into Normal mode to enable the transmitter.
DS20005533A-page 4
2016 Microchip Technology Inc.
MCP2557FD/8FD
FIGURE 1-1:
MCP2557FD/8FD STATE DIAGRAM
From any
State
V
DD
< V
PORL
Or
V
IO
< V
PORL
_V
IO
UnPowered (POR)
CAN High Impedance
Common Mode Tied to
GND
HS RX OFF
R
XD
High
Bandgap OFF
T
XD
Time-Out
CAN Recessive
Common Mode V
DD
/2
HS RX ON
R
XD
= f(HS RX)
V
DD
> V
PORH
And
V
IO
> V
PORH
_V
IO
T
XD
Low > Tpdt
T
XD
High
Or
And
T > TJ(SD)
T < TJ(SD)-TJ(HYST)
TXD High
And
Bandgap ok
And
V
DD
> V
UVH
And
Silent Low
Bandgap Not Ok
Or
V
DD
< V
UVL
Wake
Start Bandgap
CAN High Impedance
Common Mode Tied to
GND
HS RX OFF
RXD High
Normal
CAN Driven
Common Mode V
DD
/2
HS RX ON
R
XD
= f(HS RX)
Bandgap Not Ok
Or
V
DD
< V
UVL
And
SILENT Low
SILENT High
SILENT High
Silent
CAN Recessive (TX OFF)
Common Mode V
DD
/2
HS RX ON
RX
D
= f(HS RX)
2016 Microchip Technology Inc.
DS20005533A-page 5
MCU
京公网安备 11010802033920号
EEWORLD
