MAX13051_14 Datasheet, PDF (9/12 Pages) Maxim Integrated Products – ±80V Fault-Protected Can Transceiver with Autobaud

MAX13051
±80V Fault-Protected Can Transceiver
with Autobaud
Table 1. Mode Selection Truth Table
CONDITION FORCED AT PIN RS
V_RS ≤ 0.3V x V_CC
0.4V x V_CC < V_RS ≤ 0.6V x V_CC
V_RS ≥ 0.75V x V_CC
MODE
High Speed
Slope Control
Standby
RESULTING CURRENT AT RS
200µA ≤ _|I_RS| ≤ 500µA
10µA ≤ _|I_RS| ≤ 200µA
|^IRS| ^{≤ 10µA}
Table 2. Transmitter and Receiver Truth Table when Not Connected to the Bus
TXD
RS
Low
High or Float
X
V_RS ≤ 0.75V x V_CC
V_RS ≤ 0.75V x V_CC
V_RS ≥ 0.75V x V_CC
*Common-mode input resistance.
CANH
High
V_CC / 2
R_ICM GND
CANL
Low
V_CC / 2
R_ICM GND
BUS STATE
Dominant
Recessive
Recessive
RXD
Low
High
High
TXD
RXD
AUTOBAUD
TXD
CANH - CANL
RXD
Figure 4. MAX13051 Autobaud Timing Diagram
TRANSMITTER
INPUT
RECEIVER
OUTPUT
Transmitter
The transmitter converts a single-ended input (TXD)
from the CAN controller to differential outputs for the
bus lines (CANH, CANL). The truth table for the trans-
mitter and receiver is given in Table 2.
TXD Dominant Timeout
The MAX13051 provides a transmitter-dominant timeout
that prevents erroneous CAN controllers from clamping
the bus to a dominant level by maintaining a continuous
low TXD signal. When the TXD remains in the dominant
state for greater than 1ms (max), the transmitter
becomes disabled, driving the bus line to a recessive
state (Figure 5). After a dominant timeout fault, the
MAX13051’s transmitter becomes enabled upon
detecting a rising edge at TXD.
Receiver
The receiver reads differential inputs from the bus lines
(CANH, CANL) and transfers this data as a single-
ended output (RXD) to the CAN controller. It consists of
a comparator that senses the difference, V_DIFF =
(CANH - CANL), with respect to an internal threshold of
0.7V. If this difference is positive, (V_DIFF > 0.9V), a
logic-low is present at RXD. If negative, (V_DIFF < 0.5V),
a logic-high is present. The receiver always echoes the
CAN bus data when not operating in autobaud mode.
Maxim Integrated
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