MCP2551 Microchip Technology, MCP2551 Datasheet - Page 5

• Manufacturer Part Number: MCP2551
• Description: High-Speed CAN Transceiver
• Manufacturer: Microchip Technology

1.5
If the MCP2551 detects an extended low state on the
TXD input, it will disable the CANH and CANL output
drivers in order to prevent the corruption of data on the
CAN bus. The drivers are disabled if TXD is low for
more than 1.25 ms (minimum). This implies a maxi-
mum bit time of 62.5 µs (16 kb/s bus rate) allowing up
to 20 consecutive transmitted dominant bits during a
multiple bit error and error frame scenario. The drivers
remain disabled as long as TXD remains low. A rising
edge on TXD will reset the timer logic and enable the
CANH and CANL output drivers.
1.6
When the device is powered on, CANH and CANL
remain in a high-impedance state until V
voltage level V
remain in a high-impedance state if TXD is low when
V
active only after TXD is asserted high. Once powered
on, CANH and CANL will enter a high-impedance state
if the voltage level at V
voltage brown-out protection during normal operation.
1.7
The 8-pin pinout is listed in Table 1-3.
TABLE 1-3:
1.7.1
TXD is a TTL compatible input pin. The data on this pin
is driven out on the CANH and CANL differential output
pins. It is usually connected to the transmitter data out-
put of the CAN controller device. When TXD is low,
CANH and CANL are in the dominant state. When TXD
is high, CANH and CANL are in the recessive state,
provided that another CAN node is not driving the CAN
bus with a dominant state. TXD has an internal pull-up
resistor (nominal 25 k
Number
DD
2002 Microchip Technology Inc.
Pin
1
2
3
4
5
6
7
8
reaches V
TXD Permanent Dominant
Detection
Power-on Reset
Pin Descriptions
TRANSMITTER DATA INPUT (TXD)
CANH
Name
CANL
RXD
V
TXD
V
PORH
V
Pin
R
REF
PORH
DD
SS
S
MCP2551 PINOUT
. In addition, CANH and CANL will
. CANH and CANL will become
DD
Transmit Data Input
Ground
Supply Voltage
Receive Data Output
Reference Output Voltage
CAN Low-Level Voltage I/O
CAN High-Level Voltage I/O
Slope-Control Input
to V
falls below V
DD
).
Pin Function
PORL
DD
reaches the
, providing
Preliminary
1.7.2
Ground supply pin.
1.7.3
Positive supply voltage pin.
1.7.4
RXD is a CMOS-compatible output that drives high or
low depending upon the differential signals on the
CANH and CANL pins and is usually connected to the
receiver data input of the CAN controller device. RXD
is high when the CAN bus is recessive and low in the
dominant state.
1.7.5
Reference Voltage Output (Defined as V
1.7.6
The CANL output drives the low side of the CAN differ-
ential bus. This pin is also tied internally to the receive
input comparator.
1.7.7
The CANH output drives the high side of the CAN dif-
ferential bus. This pin is also tied internally to the
receive input comparator.
1.7.8
The R
or Standby modes via an external biasing resistor.
S
pin is used to select High-Speed, Slope-Control
GROUND SUPPLY (V
SUPPLY VOLTAGE (V
RECEIVER DATA OUTPUT (RXD)
REFERENCE VOLTAGE (V
CAN LOW (CANL)
CAN HIGH (CANH)
SLOPE RESISTOR INPUT (R
MCP2551
SS
DD
DS21667C-page 5
)
)
DD
REF
/2).
S
)
)