LT1796CS8 datasheet(5/8 Pages) LINER

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LT1796

1796f

PI FU CTIO S

TXD (Pin 1): Driver Input. Logic-level thresholds are set by

VREF. A logic input level higher than VREF turns the driver

outputs off, releasing control of the CANH and CANL lines.

A logic input less than VREF turns the driver outputs on,

pulling CANH high and CANL low. An open TXD input will

float high, turning the driver outputs off. The TXD input pin

can withstand voltages from – 0.3V to 44V with no dam-

age.

GND (Pin 2): Ground.

VCC (Pin 3): Positive Supply Input. Normal operation is

with a 4.75V to 5.25V supply. Operation with supplies up

to 44V is possible with unterminated bus lines. Operation

at high voltages with normally terminated busses will

result in excessive power dissipation and activation of the

thermal shutdown circuit. VCC should be decoupled with

a 0.1

µFlowESRcapacitorplacedasclosetothesupplypin

as possible.

RXD (Pin 4): Receiver TTL Level-Logic Output. A high level

output indicates a recessive state (zero-volt differential)

bus. A dominant state forces a low receiver output.

VREF (Pin 5): Reference Output. The reference voltage sets

the TXD input threshold and the recessive bus common

mode voltage at CANH and CANL. VREF is approximately

VCC/2 for low voltage operation. When VCC > 7.5V, VREF

maintains a 3.5V level.

CANL (Pin 6): CAN Bus Low Data Line. The CANL pin is one

input to the receiver and the low driver output. In the

dominant state (TXD low), the driver pulls the CANL pin to

within 1V of GND. In the recessive state (TXD high), the

driver output stays high impedance. The CANL pin is

protected from voltage faults from – 60V to 60V in domi-

nant, recessive, standby or powered off modes. On-chip

ESD protection meets IEC-1000-4-2 levels.

CANH (Pin 7): CAN Bus High Data Line. The CANH pin is

one input to the receiver and the high driver output. In the

dominant state (TXD low), the driver pulls the CANH pin to

within 1V of VCC. In the recessive state (TXD high), the

driver output stays high impedance. The CANH pin is

protected from voltage faults from – 60V to 60V in domi-

nant, recessive, standby or powered off modes. On-chip

ESD protection meets IEC-1000-4-2 levels.

RS (Pin 8): Slope Control. This pin is a multifunction

control pin. When RS is high (VRS > 4V), the circuit goes

into a low power standby mode. In standby, the driver

always stays in a high impedance (recessive) state. The

receiver operates in a low power (slow) monitoring mode.

Received data may be used to “wake-up” the system to full

functionality. Full speed normal operation occurs if RS is

tied low through a resistance of less than 3k. The current

out of RS will be limited to about 500µA in the low state.

Controlling the current out of RS with a resistor greater

than 3k or by using a current source allows slew rate

control of the data output onto CANH and CANL.

TYPICAL PERFOR A CE CHARACTERISTICS

Receiver Thresholds vs

Temperature

Receiver Propagation Delay vs

Temperature

TEMPERATURE (

°C)

–50

0.80

0.75

0.70

0.65

0.60

–25

1796 G10

100

VTH RISING

VTH FALLING

TEMPERATURE (

°C)

400

350

300

250

200

1796 G11

–50

–25

100

tRXDOFF

tRXDON

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