I opened a support case about thisabout a week ago on invitation from a Cypress employee, but it has been completely ignored. The employee wrote to me, unsolicited, for help with his app note then said I should raise a case about my questions rather than him answering them as it was not his problem. Here's the case which is being ignored:

Subject

FX3 Power supplies

Description

I need to know the current requirement of the VBUS pin. The data sheet speaks of a large number of separate supply pins but only mentions two current values without relating these to the voltage names. So there is no way to know how much current is drawn by VBUS. Is it ICC USB? Or is it just a supply for the tranceiver and pullups and therfore much smaller?

I am making a self powered device. I believe I can supply 5V to VBUS on the FX3, from a supply rail in my device, but only connect it when the host is connecting 5V to the receptacle. This should avoid damage from excessive external supplies.

I then also have to know what to do with VBATT as I don't have a battery. My best guess is to connect it also to 3.3V or 5V, though I have no idea how to justify this as VBATT is not really explained.

At any rate this requires me to be able to estimate the power required by these pins.

The other question I have is whether there is any need or benefit from power supply sequencing?

Hi,

We are extremely sorry about the inactivity in the case. Please let us know the case number, I will take a look and take necessary actions.

Regarding VBAT....

FX3 can select whether to use VBUS or VBATT to power USB PHY. Generally VBATT is used to power FX3 in case if it is acting as USB Host in OTG mode, where battery voltage can vary to large extend (VBATT supply voltage range 3.2V to 6V).

If FX3 is acting as USB 3.0 Device mode, you can leave VBATT unconnected or you might want to connect VBATT to 3.3V using 0 ohm resistor(we recommend). You need to use VBUS (4.1 V to 6 V input from USB connector VBUS) to power USB PHY. The pin VBUS connects to the VBUS of USB connector, so its range is from 4.1 V to 6 V.

VBATT: This is the 3.2 V to 6 V power input for the USB PHY. It can be connected from the battery powered by external battery, or regulated 3.3V powered by the external power management IC. This supply input powers the USB PHY through an internal voltage regulator of FX3. This supply is internally regulated to 3.3 V for the USB PHY.

Regarding VBUS...

As I already mentioned VBUS pin of FX3 should be connected to VBUS signal of USB connector.  This is mandatory for the connect/disconnect detection to work properly. 

Regarding power sequencing...

There is no Power sequencing requirements for FX3. It can be powered simultaneously (all the supplies).

Regards,

Gayathri

OK Thanks. But I still don't know how much current VBUS takes worst case.

 I will check with the design team and get back to you on this.

Regards,

Gayathri

Thanks - I  look forward to that.

The two current values that are mentioned in the data sheet are as follows:

ICC Core: Current through all the 1.2V supplies combined. This includes VDD, AVDD, U3RXVDDQ, U3TXVDDQ.

ICC USB: It is the current through the VBUS or VBATT supply that is connected to the FX3.

I am not sure if you looking for the current through the VBUS pin connected to the FX3 or you are looking for the whole current that has been taken from the VBUS of the USB host. Please let me know.

Thanks,

sai krishna.

Hi,

In the datasheet of FX3, nothing is specified about I/O operating Current (VIO1-5). Assume that i am using all the 32 datalines.

Thanks,

Kasthuri Rangan V

Yes. We are not talking about the I/O power consumption numbers in the data sheet as it will completley depend up on the usage (voltage, duty cycle) and the number of I/Os.

Thanks,

sai krishna.

Hi Sai,

 Thanks for you info.. Am now using 8 databits and 3-4 Control bits as GPIOs at I/O level 3.3V. Can you just say approximate value of input current required.

Also, Are all the VIO domains configurable to 2.8V?

Thanks,

Kasthuri Rangan V

Current consumption in your case will be around 53mA. This is calculated by assuming that all the 12 I/Os have activity factor of 50, @3.3V.

Thanks,

sai krishna.