USB Port

Thread Starter

biferi

Joined Apr 14, 2017
162
I am Looking at a SamSung TV Model UN75TU8000FXZA.

They Say it has 2. USB Ports.
A USB2. Port that is 5. Volts at 0.5 A.
And the other USB Port is 5. Volts at 1. A.

This does not sound Right to Me?
USB2. is 5. Volts at .005mA am I Right?

I do not know of any USB Ports that give 1. Amp.

Can You Tell Me what Type of USB Ports this TV has?
 

Irving

Joined Jan 30, 2016
2,111
USB2 is 5v @ 500mA as standard. The Usb standard mandates 500mA as a minimum, but there is no maximum (other than limited by the contacts). A Quick Charger can typically supply 2A. Many TV have a USB port that can power an external hard drive for recording, or a set-top box, or external video source, eg an Amazon FireStick or a Roku dongle...
 

Papabravo

Joined Feb 24, 2006
16,834
I am Looking at a SamSung TV Model UN75TU8000FXZA.

They Say it has 2. USB Ports.
A USB2. Port that is 5. Volts at 0.5 A.
And the other USB Port is 5. Volts at 1. A.

This does not sound Right to Me?
USB2. is 5. Volts at .005mA am I Right?

I do not know of any USB Ports that give 1. Amp.

Can You Tell Me what Type of USB Ports this TV has?
According to the USB 2.0 Standard which has been out for a decade and a half, a USB master should supply at least 100 mA by default. A USB device can "negotiate" with the USB master for more, but it has to do this by using the USB protocol. So +5 V at 0.5 Amperes and +5V at 1 Ampere are entirely reasonable propositions. I would point out that 1 Ampere through an AWG #28 wire is pushing the capability of the wire just a bit. If you're going to do that the connecting cable should be as short as possible.
 

Irving

Joined Jan 30, 2016
2,111
According to the USB 2.0 Standard which has been out for a decade and a half, a USB master should supply at least 100 mA by default. A USB device can "negotiate" with the USB master for more, but it has to do this by using the USB protocol. So +5 V at 0.5 Amperes and +5V at 1 Ampere are entirely reasonable propositions. I would point out that 1 Ampere through an AWG #28 wire is pushing the capability of the wire just a bit. If you're going to do that the connecting cable should be as short as possible.
The USB standard defines a 'unit load' (UL) as 100mA for USB2 and 150mA for USB3. A USB device may draw 5 UL on USB2 (500mA) and 6 on USB3 (900mA) without negotiation, these are guaranteed by the standard. A port can indicate higher output capability by different resistances between power and data lines and a device can test these to determine how much current can be drawn. A USB port pin is good for 5A.
 

Papabravo

Joined Feb 24, 2006
16,834
The USB standard defines a 'unit load' (UL) as 100mA for USB2 and 150mA for USB3. A USB device may draw 5 UL on USB2 (500mA) and 6 on USB3 (900mA) without negotiation, these are guaranteed by the standard. A port can indicate higher output capability by different resistances between power and data lines and a device can test these to determine how much current can be drawn. A USB port pin is good for 5A.
I understood that 500 mA was the maximum and that a 'function' (USB for device) was only allocated 100 mA without negotiation.
 

Irving

Joined Jan 30, 2016
2,111
I understood that 500 mA was the maximum and that a 'function' (USB for device) was only allocated 100 mA without negotiation.
Not so... look at all those usb 'add-ons' like lights, fans, etc that have no intelligence but power up happily on just the + & - wires...
 

dl324

Joined Mar 30, 2015
13,143
Not so... look at all those usb 'add-ons' like lights, fans, etc that have no intelligence but power up happily on just the + & - wires...
It is so. USB hosts are required to supply 1 load to any device. A device can negotiate for up to 5, but must operate in a low power mode if the request is refused.

Lights and fans are considered "decorations" and are not USB compliant.
 

Thread Starter

biferi

Joined Apr 14, 2017
162
I Ask because I called SamSung and they Told Me 1. USB Port was 5. Volts at .05 Amp.
And the other USB Port was 5. Volts at 1. Amp.

This is what I did not understand?
 
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