Maximum voltage range -- beaglebone revA5 power supply.

[Kottas Dimitris]

High, all.
Do you know the input voltage the beaglebone Rev A5 can tolerate?
Has anyone tried voltage above 5V or it is sure it will burn?

[Gerald Coley]

5.2V is the max. Go past that and bad things will happen. USB is 5.2V max. Plug in something higher than that and the board will not power up. It should not burn up, just won't power up. Now if you put 100V on it, all bets are off.

 

Gerald

 

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Gerald

 

ger...@beagleboard.org

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[sa_Penguin]

Damn. The cheap little power supply I wanted to use is 2.5A... but it's running high, at 5.5V.

So far, my attempts to load it down have failed.  Looks like I need a 0.4V drop.

A couple of germanium diodes with a resistor in parallel should do.

Any recommendations for a quick voltage drop?

-- Alan Campbell

[lorena...@gmail.com]

Just dug into this... My notes:

BBB Power: 

No onboard input voltage regulation! Input jack connects directly to TPS65217C PM IC. 

From tps65217c.pdf:

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                               Absolute Maximum Supply voltage range, USB, AC: -0.3 to 20 V

RECOMMENDED OPERATING CONDITIONS - Supply voltage, USB, AC: 4.3 to 5.8 V

                                                            Maximum Input current from AC: 2.5 A

                       VIN(OVP) Input over voltage detection threshold USB, AC: 5.8 (typ)6 (max)6.4 V

provides a linear battery charger for single-cell Li-ion and Li-Polymer batteries... 

-----

The 5V rails VDD_5V and SYS_5V go to the LEDs, the expansion connector, the DVI/HDMI connector, and the USB connectors. Unless you are using these for something which needs regulated +5V, the wider 4.3 to 5.8 V limits will keep the board itself happy. 

It will safely disconnect from an input that exceeds about 6V, and can then handle up to 20V. But it is _not_ protected from reverse polarity! 

[Gerald Coley]

And if you go to 6V, it will blow up the power control switch for the USB host, rated at 5.5VDC maximum. 

Gerald

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[Loren Amelang]

I see the TPS2051 in the USB Host section of the schematic, but it is fed from SYS_5V. Isn't that _after_ the TPS65217C shuts everything off when the input voltage exceeds an average of 6V? 

I guess if you're being absolutely proper, the 2051 says 6.0V absolute max and the 65217 says it limits to a max of 6.4V even though 6.0V is typical. 

But the 2051 says output voltage range is -0.3 V to V(IN) + 0.3 V, so the internal transistor must be able to handle at least 6.3V...  And I'd be amazed if they couldn't handle far more unless they are trying to feed a current overload - from which they should protect themselves. Seems like since these are both TI products, they'd be designed to work together?  

So my real question - do you actually see these frying in the real world? 

[Gerald Coley]

The TPS65215C passes what ever voltage is supplied to it out heat pin as long as it is not over 7.2V, which is mote than 5V. So, while the TPS65217C can run at 6V, the TPS2051 cannot,. 

Gerald

[Loren Amelang]

Trying to understand this...  It seems you are saying the default state of the TPS65215C is to have the AC pin internally connected to the USB pin. But the datasheet says:

-----

AC input is prioritized over USB input, i.e. if both inputs are valid, current is pulled from the AC input and not USB. If both, AC and USB supplies are available, the power-path switches to USB input if VAC drops below 4.1 V (fixed threshold).

Note that the rise time of VAC and VUSB must be less than 50 ms for the detection circuits to operate properly. If the rise time is longer than 50 ms, the IC may fail to power up.

The linear charger periodically applies a 10-mA current source to the BAT pin to check for the presence of a battery. This will cause the BAT terminal to float up to > 3 V which may interfere with AC removal detection and the ability to switch from AC to USB input. For this reason, it is not recommended to use both AC and USB inputs when the battery is absent.

-----

So there is the official word on all the power supply rise-time issues people report! 

-----

AC and USB Input Discharge

AC and USB inputs have 90-µA internal current sinks which are used to discharge the input pins to avoid false detection of an input source. The AC sink is enabled when USB is a valid supply and VAC is below the detection threshold. Likewise, the USB sink is enabled when AC is a valid supply and VUSB is below the detection limit.

Both current sinks can be forced OFF by setting the [ACSINK, USBSINK] bits to 11b. Both bits are located in register 0x01 (PPATH).

-----

There is an even more important reason for never having AC and USB connected simultaneously. 

Sure sounds to me like the TPS65215C never turns on both FETs at the same time. 

But as I asked before, the reality is best known from the RMA stream - do people actually fry their TPS2051 switches? 

Loren

[Gerald Coley]

Yes, we test the TPS2051 every time we test a board. It is standard practice. And we have gotten very god at replacing them when the use connects 6V to them because they don't read the manual or the label on the connector.. 

Gerald

[Dimitris Kottas]

On Thu, Apr 12, 2012 at 7:54 PM, Gerald Coley <ger...@beagleboard.org> wrote:

5.2V is the max. Go past that and bad things will happen. USB is 5.2V max. Plug in something higher than that and the board will not power up. It should not burn up, just won't power up.

Ok got it. 

Now if you put 100V on it, all bets are off.

Hahaha, thank you.