ISO8200BQ RDS(on)

[Msys]

Dear All,

I'm using the evaluation board STEVAL-IFP033V1 Galvanically-isolated 8 channel high-side driver based on the ISO8200BQ.

I powered the board with 22.8VDC, all outputs on from the isolated side (all LEDS green on the output connector)

I checked the short circuit behavior and it works fine.

With a single resistive load on output 5, equal to 15 ohms, the measured output current is about 1.4 A continuous.
The temperature of the chip becomes very hot, above 130°C in these conditions, and with the oscilloscope we never have the fault signal active, not even for brief moments, and this could be ok.

The problem seems to be the output voltage, however, which decreases by about 5.8V compared to the input supply voltage, (the output drops at17V)
Consequently the RDSon of the device is equal to about 4ohm, very far from the 0.24max reported in the datasheet, in this condition the operating range of the output is very low, not in operating range for the device, and we have no fail indication.

Please, check if the RDSon is different as reported, or if this i a normal opertating condition for this device, and we have to find different part number, because this is not acceptable for us.

Thanks for the support

[Peter BENSCH]

Welcome @Msys, to the community!

With your current of 1.3A and the observed voltage drop, you are already within the internal current limitation that protects the device from overload. So it has nothing to do with an apparently higher Rdson. You will also find a note  on the first page of the ISO8200BQ data sheet under features: ‘IOUT = 0.7 A (per channel)’. Table 6 then shows the values 0.7A (min), 1.3A (typ) and 1.9A (max) for Ilim. It is therefore not a good idea to draw more than 0.7A out of a single channel.

However, you could consider connecting two outputs in parallel via tracks that are as balanced as possible and thus doubling the total current, which would of course only result in 4 total channels per device.

Hope that helps?

Regards
/Peter