LTC4331 datasheet(16/22 Pages) AD

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LT3960

Rev. B

For more information www.analog.com

±36V Extended Common-Mode Range

The LT3960 receiver features an extended common

mode range of -36V to 36V when operating from a 5V

VCC and -25V to 25V when operating from a 3.3V VCC.

The wide common mode increases the reliability of oper-

ation in environments with electrical noise or local ground

potential differences due to ground loops. This extended

common mode range allows the LT3960 to conduct I2C

communication in environments inhospitable to standard

I2C, such as between two distant PCBs in an automobile.

I2CAN Driver

When the SCL or SDA pin is asserted low by external

I2C device and the conditions are met (whether by mode

selection or bidirectional arbitration) to propagate this

data from I2C to CAN, the I2CAN driver asserts the dom-

inant state on the corresponding bus lines; the CANxH

driver pulls high and the CANxL driver pulls low. When the

SCL or SDA pin is high under these same conditions, the

I2CAN driver is in the recessive state; both the CANxH and

CANxL drivers are in the high impedance state and the bus

termination resistor equalizes the voltage on CANxH and

CANxL. In the recessive state, the impedance on CANxH

and CANxL is determined by the receiver input resistance,

RIN. When EN/MODE is low or the VCC is in UVLO, the

LT3960 is in shutdown; all I2CAN drivers are in the high

impedance state, and the receiver input resistance RIN is

disconnected from the bus by a FET switch.

Transmit Dominant Timeout Function

Both transceivers in the LT3960 include a 1.5ms (typical)

timer to limit the time that driver can hold the I2CAN bus

in the dominant state. For example, if the SCL line is held

low in Master Mode, a dominant state is asserted on the

CANSCL bus until the timer expires, after which the driver

releases the bus to a recessive state. The timer is reset

when SCL is brought high.

I2CAN Driver Overvoltage, Overcurrent, and

Overtemperature Protection

The I2CAN driver outputs are protected from short cir-

cuits to any voltage within the absolute maximum range

of -40V to 40V. The maximum current on I2CAN interface

pins in a fault condition is ±150mA. The drivers include a

progressive foldback current limiting circuit that contin-

uously reduces the driver current with increasing output

fault voltage. The fault current is typically ±2mA for faults

at the absolute maximum voltages of ±40V.

The LT3960 also features thermal shutdown protection

that disables the chip in the case of excessive power

dissipation from the drivers. When the die temperature

exceeds 168 ˚ C (typical), the LT3960 is forced into shut-

down mode and the I2CAN drivers enter a high impedance

state.

Power-Up/Down Glitch-Free Outputs

The LT3960 employs an undervoltage monitoring circuit

on the VCC supply to control the activation of the trans-

ceiver circuitry. During start-up SDA, SCL, and all I2CAN

outputs are in a high impedance state until VCC reaches a

voltage sufficient to reliably operate the chip. At this point,

if EN/MODE is out of its shutdown region, the chip acti-

vates. The CANSCL and CANSDA receivers activate after

a short delay tEN;I2C allowing SCL or SDA to follow the

state of CANSCL or CANSDA. The CANSCL and CANSDA

drivers power up in the transmit dominant timeout state

regardless of the state of SCL or SDA and remain in the

recessive state until the first high to low transition of SCL

or SDA, respectively. This assures that the LT3960 does

not disturb the I2CAN bus by glitching to the dominant

state during start-up.

During power-down, similar protection exists. When the

undervoltage detection circuit senses low supply voltage

on VCC, it immediately puts the chip into shutdown. All

I2C and I2CAN pin outputs go the high impedance state.

APPLICATIONS INFORMATION

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