Power Over CoaXPress

The Power Transmitting Unit – PTU – is responsible for a safe delivery of power.

It fulfills all the requirements of the CoaXPress standard for a CoaXPress Host, namely:

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It is capable of delivering up to 17 W of 24 V DC power to the connector

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It implements an over-current protection device – OCP

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It supports the CoaXPress PoCXP detection method

In addition, it provides the application with the capability of:

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Controlling the PoCXP automatic detection

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Disabling or interrupting the power delivery

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Resetting the OCP when tripped

Applies to:

All the PTU's of a PCI Express Coaxlink card are powered by an external 12 V power supply through an on-board 12 V to 24 V power converter on the Coaxlink card.

The external 12 V supply is attached to the auxiliary power input connector through a 6-pin PEG cable.

Note: The 12 V supply is typically delivered by the power supply of the Host PC.

The AuxiliaryPowerInput feature reports the status of the connection made by the PEG cable between the external power supply and the Coaxlink auxiliary power input connector.

The CxpPoCxpPowerInputStatus feature reports the status of the 24 V power converter.

Applies to:

All the PTU's of a PCIe/104 Coaxlink card are powered by an external 24 V power supply.

The external 24 V supply is attached to the auxiliary power input connector through a 4-pin cable.

The AuxiliaryPowerInput feature reports the status of the connection made by the power cable between the external power supply and the Coaxlink auxiliary power input connector.

The CxpPoCxpPowerInputStatus feature reports the status of the 24 V input.

On execution of the CxpPoCxpAuto command the PTU controller initiates a PoCXP device detection procedure.

If the PoCXP device detection procedure terminates successfully, the PTU applies power by closing the switch.

If the PoCXP device detection procedure fails, the controller doesn't apply power and retries a new PoCXP detection procedure. Possible causes of failure are:

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The external power is not connected (AuxiliaryPowerInput = Unconnected)

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The external power source is off (CxpPoCxpPowerInputStatus = NotOK)

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There are no camera attached

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The attached camera is not PoCXP compliant

Once the power is applied, the controller remains in that state until any of the following situations occurs:

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The application disables the power delivery by executing the PoCxpTurnOff command.

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The external power source is disconnected (CxpPoCxpPowerInputStatus = NotOK)

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The external power source is turned off (CxpPoCxpPowerInputStatus = NotOK)

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The CoaXPress cable is disconnected (The average output current measured over a time interval of 0.3 seconds is less than 8 mA)

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The OCP trips (The output voltage drops for a time interval greater than 20 milliseconds)

On execution of the CxpPoCxpTurnOff command the PTU turns off the switch and disables PoCXP powering. In that state, the PTU is not performing PoCXP detection procedures.

The CxpPoCxpConfigurationStatus feature reports the configuration status of the PTU: Off or AUTO

The CxpPoCxpStatus feature reports the status of the PTU: Off, On or Tripped.

IMPORTANT NOTE
	For users of early versions of the Coaxlink Driver Since version 3.1 of the Coaxlink Driver, PoCXP powering is enabled at system power-up. Consequently, when using PoCXP powered camera(s), the application is not anymore required to enable PoCXP powering by issuing a CxpPoCxpAuto command.

The OCP circuit is built with a PTC device providing two kind of protections:

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The overload protection addresses the cases when the load is excessive.

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The short-circuit protection addresses the cases of accidental short-circuits.

In case of overload, the PTC trips (= opens progressively the circuit) after several seconds or minutes depending on the current level and the ambient temperature. The higher the current, the lower the time to trip. The same applies to the ambient temperature.

In case of short-circuit, the PTC trips immediately. Consequently, the PTU controller enters the tripped state and opens the switch. The tripped PTC device returns to the conducting state after having cooled down. This may take a few seconds. However, the PTU controller remains in the tripped state until the application issues a CxpPoCxpTripReset command. Having left the tripped state, the PTU can initiate a new PoCXP device detection and, if successful, re-establish power.

Note: The PTC is sized to sustain 17 W of power over the whole operating temperature range without tripping.

Note: Extracting more than 17 W of power and/or operating the Coaxlink card above the operating temperature range is prohibited since it may induce unexpected PTC trips.