Model 7055-B Output Current Capability Topic is solved

[brumbarchris]

Good afternoon everyone,
I would like to know what the output current capability of the Model 7055-B is in both of the following scenarios:
- Scenario1: powered by USB bus, no separate power supply (host PC current supply capability 500mA)
- Scenario2: powered by USB bus, no separate power supply (host PC current supply capability 900mA)
- Scenario3: powered through the AUX supply

The datasheet specifies the 0.5A figure, which cannot be really valid for Scenario1, considering the efficiency of the internal DC-DC converter.

Is there a recommended power supply to be used with the AUX input that will guarantee meeting the output noise figures mentioned in the datasheet? (these are: 2.5 / 3 / 6uV for Model 7055-B)

Thank you and best regards,
Cristian

[Daniel (Intona)]

The noise figure can be guaranteed only when using the internal DC-DC and not the AUX port. This is because the AUX will be switched to the device port directly using a relay, effectively disabling the internal regulator.

About the other questions, we will take some measurements and present them here in the next days.

[brumbarchris]

Super, thank you for the reply. And also, looking forward to the rest of the information.

Concerning the AUX port, is there a document detailing the pinout or is it according to the standard USB Micro pin configuration? I would not want to supply it with reverse polarity...

Best regards,
Cristian

[Daniel (Intona)]

The AUX port follows Micro-USB specification. Only +VBUS and GND are used. The data lines are AC-grounded (via capacitor, for EMI reasons) and can be viewed as "not connected".
If you reverse the polarity, your AUX supply will be just shorted by the reverse diode of the detector MOSFET. If your supply is strong enough, this part will produce magic smoke after a while.

[Florian (Intona)]

Hi Cristian, coming to your initial question:
The7055-B has the ability to source 500mA at the USB A port. Of course this depends directly on the host PC current capability.
The 7055-B itself has a nominal current draw of 200mA.
Assuming that your ports are strictly current limited to 500mA/900mA this means:
- Scenario 1: 300mA
- Scenario 2: 500mA
- Scenario 3: Dependent on your PSU (2A max.)
Hopefully this answers your question.

[brumbarchris]

Thank you very much for the clarifications!

Be advised that I have initiated an ordering process (there is a specific department in our company dealing with orders) for a 7055-B.
I must admit that, apart from the technical requirements being met, the compelling argument to get this device was "made in Germany" (as opposed to just "designed in Germany", which some products advertise).

Best regards,
Cristian

[onlyoneme]

Is this - "the AUX will be switched to the device port directly using a relay, effectively disabling the internal regulator", I guess no filtering at all - valid also for 7055-D? If so, how the current is limited to 2000mA?

[Florian (Intona)]

Is this - "the AUX will be switched to the device port directly using a relay, effectively disabling the internal regulator", I guess no filtering at all - valid also for 7055-D? If so, how the current is limited to 2000mA?

This is also valid for the 7055-D.
The output current is limited by using a ptc reset fuse. Consequently not strictly limited to 2000mA, the ptc fuse is meant to serve as a short circuit protection.

[onlyoneme]

Is this - "the AUX will be switched to the device port directly using a relay, effectively disabling the internal regulator", I guess no filtering at all - valid also for 7055-D? If so, how the current is limited to 2000mA?

This is also valid for the 7055-D.
The output current is limited by using a ptc reset fuse. Consequently not strictly limited to 2000mA, the ptc fuse is meant to serve as a short circuit protection.

Thank you.