# CAN Transceiver Current Draw

I'm trying to determine the input current required to operate the following SN65HVD233 CAN transceiver at 1Mbaud: http://www.ti.com/lit/ds/symlink/sn65hvd233.pdf

The first spec I see listed is receiver output current:

I don't understand why this ranges from -10 to 10mA. The receiver outputs to the CAN controller's Rx pin so why would it be sinking current?

The next spec I see is output current for the driver:

Again, I'm not sure why the driver would be sinking current.

Schematic provided on datasheet of driver and receiver:

Later in the datasheet, the supply current for the driver and receiver is provided:

(both driver and receiver are identical, with 6mA of current draw in dominant and recessive state)

These are specified at "No load" - can I use these figures for power calculations when the device is actually attached to a bus?

Also, do the high level and low level output currents for driver and receiver factor into the current draw of the transceiver?

• It might be worth mentioning that the $I_o$ receiver current is under the absolute maximum ratings. Meaning if you go beyond it, things can break. Jul 29, 2019 at 2:03
• Yes, I can see why trying to drive a load requiring more than 10mA with the receiver is an issue - just can't see why there is a -10mA minimum rating
– user202237
Jul 29, 2019 at 2:07

Since the driver is capable of sourcing 50mA max and the receiver is capable of sourcing 10mA max, 60mA is the worst case current consumption of the transceiver.

The Receiver must be able to produce strong pullups and strong pulldowns; thus the +-10mA.

You may also care about the current from the CAN bus into the Receiver. For large common-mode range, that will use two matched voltage dividers, likely tied to the internal Bus Termination Voltage. Expect such resistor values as 10Kohm in series with 1Kohm, or perhaps much higher, depending on the Receiver timeconstant (bandwidth) needed.

• So based on the datasheet parameters, how should I be calculating the transceiver's current draw?
– user202237
Jul 29, 2019 at 3:40
• Do you want the current pulled from the CAN bus, so the Receiver circuitry can decide if Dominant or Recessive? or the current pulled (drawn) from the VDD pin to operate the transistors inside the Receiver circuitry? that is show as Maximum of 6 milliAmps. Given the large variations with (1) foundary doping, (2) VDD variations, (3) temperature effects, (4) etc, I'd expect your nominal is 3mA or 2mA. Jul 29, 2019 at 13:42
• I'd like to know the total current required at the Vdd pin for the transceiver. Since the driver is capable of sourcing 50mA max and the receiver is capable of sourcing 10mA max, should I consider 60mA my worst case current consumption?
– user202237
Jul 29, 2019 at 14:09
• I understand now. You want to know how to size the power-supply. Your thinking seems clear, to me. Jul 30, 2019 at 1:35