Slope Control

Connect a resistor from RS to ground to select slope

control mode (see Table 2). In slope control mode, the

gates of the line drivers are charged with a controlled

current, proportional to the resistor connected to the RS

pin. Transmission speed ranges from 40kbps to 500kbps.

Controlling the rise and fall slope reduces EMI and allows

the use of an unshielded twisted pair or a parallel pair of

wires as bus lines. The transfer function for selecting the

resistor value is given by:

See the Typical Operating Characteristics for the Slew

Shutdown

To place the MAX3053 in shutdown, the SHDN pin

should be driven to GND. In shutdown mode, the device

is switched off. The outputs are high impedance to ±80V.

Receiver

The receiver takes differential input from the bus lines

(CANH, CANL) and converts this data to a singleended

output (RXD) to the CAN controller. It consists of a compar-

ator that senses the difference ΔV = (CANH - CANL) with

respect to an internal threshold of 0.7V. If this difference is

positive (i.e., ΔV > 0.9V), a logic low is present at the RXD

pin. If negative (i.e., ΔV < 0.5V), a logic high is present.

The receiver always echoes the transmitted data.

The CANH and CANL common-mode range is from -7V

to +12V. RXD is logic high when CANH and CANL are

shorted or terminated and undriven.

Thermal Shutdown

If the junction temperature exceeds +160°C, the device is

switched off. The hysteresis is about 20°C, disabling ther-

mal shutdown once the temperature declines to +140°C

and the device is turned back on.

Autoshutdown

To manage power consumption, autoshutdown puts the

device into shutdown mode after the device has been

inactive for a period of time. The value of an external

threshold of inactivity time, after which the autoshutdown

triggers (see Typical Operating Characteristics).

of 20ms. Change the capacitor value according to the

following equation to change the threshold time period:

(nf)

CC

I

(µA) TIME(ms)

C

(V

V

(V))

×

=

−

SHDN

SHDN

SHDN

Drive SHDN high to force the MAX3053 on and disable

autoshutdown.

When the MAX3053 is in shutdown mode, only the wake-

up comparator is active, and normal bus communication

is ignored. The remote master of the CAN system wakes

up the MAX3053 with a signal greater than 9V on CANH.

The local CAN controller wakes up the MAX3053 by driv-

ing SHDN high or TXD.

Driver Output Protection

The MAX3053 has several features to protect itself from

damage. Thermal shutdown switches off the device and

puts CANH and CANL into high impedance if the junc-

tion temperature exceeds +160°C. Thermal protection is

needed particularly when a bus line is short circuited. The

hysteresis for the thermal shutdown is about 20°C.

*X = Don’t care.

**As defined by ISO, bus value is one of two complementary logical values: dominant or recessive. The dominant value represents

the logical 0 and the recessive represents the logical 1. During the simultaneous transmission of the dominant and recessive bits, the

resulting bus value is dominant.

Table 1. Transmitter and Receiver Truth Table

Table 2. Mode Selection Truth Table

TXD

SHDN

CANH

CANL

BUS STATE

RXD

0

HIGH

LOW

Dominant**

0

1 or float

Recessive**

1

X*

Floating

Floating

Floating

1

CONDITION

FORCED AT PIN RS

MODE

RESULTING

CURRENT AT RS

High speed

MAX3053

±80V Fault-Protected, 2Mbps,

Low Supply Current CAN Transceiver

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