NCV7356
www.onsemi.com
12
Bus LOAD Pin
Bus LOAD Pin Description
The bus LOAD pin provides a network load impedance
program point for the CAN bus. The value of the resistor
between the CANH and LOAD pins can be adjusted to
provide adequate impedance for the bus loading
requirements as dictated by the Single Wire CAN
Specification (J2411).
The resistor between CANH and LOAD pins provides a
pull down impedance for the CANH pin. The CANH driver
is a pull−up amplifier with no sink capability.
The bus LOAD pin also provides the detection circuitry
for loss of ground detection to insure there are no loading
effects on the bus should the ground connection be lost to
the NCV7356 device. During a system loss of ground
event, CANH with the 6.49 kW resistor between CANH and
LOAD will affect the bus with only between −50 mA and
10 mA of current (Bus Leakage Current During Loss of
Ground).
Resistor ground connection with internal open−on−loss−
of−ground protection
When the ECU experiences a loss of ground condition,
this pin is switched to a high impedance state.
The ground connection through this pin is not interrupted
in any transceiver operating mode including the sleep
mode. The ground connection only is interrupted when
there is a valid loss of ground condition.
This pin provides the bus load resistor with a path to
ground which contributes less than 0.1 V to the bus offset
voltage when sinking the maximum current through one
unit load resistor. This path exists in all operating modes,
including the sleep mode.
The transceiver’s maximum bus leakage current
contribution to V
ol
from the LOAD pin when in a loss of
ground state is 50 mA over all operating temperatures and
3.5 < V
BAT
< 27 V.
V
BAT
Input Pin
Vehicle Battery Voltage
The transceiver is fully operational as described in the
Electrical Characteristics Table over the range 6.0 V <
V
BAT
< 18 V as measured between the GND pin and the
V
BAT
pin.
For 5.0 V < V
Bat
< 6.0 V, the bus operates in normal
mode with reduced dominant output voltage and reduced
receiver input voltage. High voltage wake−up is not
possible (dominant output voltage is the same as in normal
or high−speed mode).
The transceiver operates in normal mode when 18 V <
V
Bat
< 27 V at 85°C for one minute.
CAN BUS
Input/Output Pin
The CANH pin is composed of a pull−up amplifier (no
sink capability) for driving the single−wire CAN bus. It is
designed to drive a 200 W load when operating in normal
mode and can operate higher 75 W loads for High−Speed
Mode. The minimum output driver capability is 50 mA, but
output shorts to ground can reach 350mA.
Normal CANH output voltages are between 4.4 V and
5.1 V. These amplitudes increase to between 9.9 V and 12.5 V
for selective system IC selection in Wake−Up Mode.
The CANH pin also acts as a bus read amplifier. The Bus
Wake−Up from Sleep Input Voltage Threshold is between
6.6 V and 7.9 V, but to maintain normal communication,
the threshold is 2.1 V.
Wave Shaping in Normal and High Voltage Wake−Up
Mode
Wave shaping is incorporated into the transmitter to
minimize EMI radiated emissions. An important
contributor to emissions is the rise and fall times during
output transitions at the “corners” of the voltage waveform.
The resultant waveform is one half of a sin wave of
frequency 50−65 kHz at the rising waveform edge and one
quarter of this sin wave at falling or trailing edge.
Wave Shaping in High−Speed Mode
Wave shaping control of the rising and falling waveform
edges are disabled during high−speed mode. EMI
emissions requirements are waived during this mode. The
waveform rise time in this mode is less than 1.0 ms.
Short Circuits
If the CAN BUS pin is shorted to ground for any duration
of time, the current is limited as specified in the Electrical
Characteristics Table until an overtemperature shutdown
circuit disables the output high side drive source transistor
preventing damage to the IC.
Loss of Ground
In case of a valid loss of ground condition, the LOAD pin
is switched into high impedance state. The CANH
transmission is continued until the undervoltage lock out
voltage threshold is detected.
Loss of Battery
In case of loss of battery (V
BAT
= 0 or open) the
transceiver does not disturb bus communication. The
maximum reverse current into the power supply system
(V
BAT
) doesn’t exceed 500 mA.
INH Pin (14 pin package only)
The INH pin is a high−voltage highside switch used to
control the ECU’s regulated microcontroller power supply.
After power−on, the transceiver automatically enters an
intermediate standby mode, the INH output will go high
(up to V
BAT
) turning on the external voltage regulator. The
external regulator provides power to the ECU. If there is no
mode change within 250 ms (typ), the transceiver re−enters
the sleep mode and the INH output goes to logic 0
(floating).
When the transceiver has detected a valid wake−up
condition (bus HVWU traffic which exceeds the wake−up
filter time delay) the INH output will become high (up to
