Tool/software:
Hi Team,
I would like to know the maximum operating current and standby current of the SN65HVD30DRG4. I couldn't find clear specifications in the datasheet. Could you please help me confirm the relevant parameters? Thank you.
Hi Sheng,
Thanks for reaching out about this question.
All supply current info can be found in this table from the datasheet:
Because SN65HVD30 is a full duplex device without enable pins, there is no standby mode where the driver and receiver can be turned off. Half duplex devices typically have separate driver and receiver enables where this standby mode is present.
Let me know if that answers your question!
Best,
Ethan
HI Sempsrott
Thank you for your reply.
I am currently estimating the system's current consumption, so I would like to obtain the maximum possible current consumption of the SN65HVD30 during normal operation.
The chip datasheet provides several current specifications, but I am unable to determine which one represents the maximum current consumption I require. As shown in the figure below, there are multiple current values listed. Could you kindly help me identify the correct one?Alternatively, could you kindly advise on the method to determine the relevant current specifications? Thank you very much.
Hi Sheng,
The first two images are specifying the max current that will break the device (if you go at or beyond that maximum value). The image that I shared is the current draw with a constant D input signal, which can be helpful when comparing to other RS-485 transceivers.
The best approximation of the current draw (aside from ordering the device and testing directly in your system) would be to the use the Power Dissipation section:
You can infer the current draw from this. This will give the worst case power draw when the driver input is a 50% duty cycle at high temperature.
Additionally, the graphs in the Typical Characteristics section are a more general guide for current consumption. Just note that we do not guarantee the performance of these graphs, but they are a helpful illustration of the device performance:
As a side note, if you are designing a new system, I would recommend using one of our newer THVD14xx transceivers (THVD1451 in particular). These transceivers have many improvements over the SN65HVDxx line of devices: improved cost structure, improved ESD protection, larger bus fault protection range to mention a few.
Let me know if that helps or if you have still have questions.
Best,
Ethan
Hi Sheng,
What made you select the SN75LBC179 and SN751178NSR?
I would highly recommend THVD1512 instead of SN75LBC179, especially if you are operating at less than 500 Kbps. This is a newer, cheaper device with a lower current consumption due to its higher efficiency. In the worst case testing scenario, the current at 500 kbps is ~45mA. So at room temp, this will be lower.
Note that the THVD15xx data sheet does supply current vs signal rate graphs, but they are only for the half-duplex devices.
As for the SN751178NSR, this is a much older device and one of our most current hungry transceivers as well. We do not spec any more details about power/current consumption than what is listed. I would recommend using 2 separate THVD1512 transceivers instead if current consumption is a concern.
If you can provide your key systems specs and criteria for your RS-485 transceivers, I can happily recommend devices for your particular system.
Best,
Ethan
Hi Sheng,
No worries Sheng, that is understandable.
For both devices, we do not have any additional current information to share aside from what is already in the datasheet.
The SN751178 only mentions the ICC supply current at 110mA with no load:
And SN75LBC179 states an average power dissipation of 330mW at 10 Mbps, VCC=5.25 with junction temp of 130C:
ICC supply current is much lower at 5mA with no load.
This is the only info we can provide for these devices. If you need additional help estimating power draw with only that info, please reference our power consumption guide which helps take into account the AC power consumption from switching losses:
https://www.ti.com/lit/ta/sszt689/sszt689.pdf
https://www.ti.com/lit/an/snoa233b/snoa233b.pdf
Best,
Ethan
