LM5066I: Calculating Telemetry Conversion Coefficients with Rsense != 1mohm

Dan Brown

Part Number: LM5066I

Table 48 in the LM5066I datasheet shows how to calculate updated current and power telemetry/warning conversion coefficient when using an Rsense resistor with any value other than 1mOhm.

The example given is "For example, if a 5-mΩ sense resistor is used, the correct coefficients for the READ_IIN command with
CL = VDD would be m = 7553, b = –65, R = –1." I am having trouble understanding how the values for m, b, and R are calculated, as they do not match the calculation in table 48.

7 months ago

0 Avishek Pal 7 months ago

TI__Mastermind 30915 points

I don't know how "m = 7553, b = –65, R = –1" was calculated for 5mΩ sense resistance. This is a very old part. My suggestion would be as follows.

m = 15076 x 5 = 75380 ⇒ 7538

b = -50.4

R= -1

0 Dan Brown 7 months ago in reply to Avishek Pal

Prodigy 40 points

Can you explain why there is a divide by 10 after the multiplication? I understand there are range limits (-32768 to 32767), but why remove the last digit? Additionally, how did you calculate b to be -50.4?

Is there a newer part you would recommend? I'm looking for an eFuse/hotswap controller to act as power switch(protector) and voltage/current monitor, ideally with I2C/PMBus communication for multiple channels.

0 Avishek Pal 7 months ago in reply to Dan Brown

TI__Mastermind 30915 points

There is a divide by 10 after the multiplication because R has become -1 from -2.

A new PMBus eFuse is under development now. Samples will be available in August 2024. If you're fine with this time schedule, we will share the details about the new device. Do you have NDA with TI?

0 Dan Brown 6 months ago in reply to Avishek Pal

Prodigy 40 points

Ah, I see.

If the new eFuse device is footprint/PMBus compatible with the LM5066I, yes I would be interested in learning more. If not, our design timelines will likely not match with the new product release.

0 Avishek Pal 6 months ago in reply to Dan Brown

TI__Mastermind 30915 points

It's not footprint compatible with LM5066i.

Power management

Power management forum

LM5066I: Calculating Telemetry Conversion Coefficients with Rsense != 1mohm