Clarification on LT8440 Support for APL Field Switch Spur Ports

Gentle Remainder! We are looking for solution ...Can someone reply with solution

Hi, 

Please find the answers below, 

1. No, It is not possible to use LT8440 in an APL Field switch. LT8440 power conditioner is designed for Class A field devices with intrinsic safety Ex ia (APL port class SLAA), which should be used in Zone 0/Div 1 hazardous area.
2. No, LT8440 provide current limiting and power limiting suitable for intrinsically safe Class A field device by monitoring the line voltage.
3. What do you mean by SCCP? If you are referring to Serial Communication Classification Protocol, then it is No, APL doesn’t require SCCP classification. APL power is defined instead by IEC TS 63444 profiles (Class A , B, C, etc.), which specify fixed voltage and current ranges rather than negotiation or classification via SCCP

Regards, 

Technical Support

Dear AnjuP ,

Thank you for your clarification regarding the LT8440 and its intended use for Class A field devices.

Since LT8440 cannot be used in an APL Field Switch implementation, we would like to understand if Analog Devices has any recommended solution or reference design for implementing APL spur ports (SPAA / SPBA) in a field switch.

We are currently using the ADIN1100 Industrial Ethernet PHY with an RGMII interface in our design.

Specifically, we are looking for a solution that can provide similar protection and monitoring features, such as:

• Current limiting and voltage limiting suitable for APL spur port power delivery
• Power cut-off capability in case of fault conditions
• Ability to monitor voltage and current variations on the spur line
• Diagnostics that can be communicated back to a local microcontroller for monitoring and control

Could you please let us know if Analog Devices offers any ICs, recommended architectures, or reference designs that support these functions for APL field switch spur ports?

Thank you for your support.

Best regards,
Chaitanya

Gentle Remainder! Can someone reply with solution

Hi Chaitanya23 ,

At your request of a solution to implement in a Field Switch, the LTC4296-1 SPoE PSE Controller would be a good fit, this device is for SPoE but its functionalities can still be used in a APL application with the requirement of adapting the circuitry for intrinsic safe area application. 

This part has been used in the following evaluation boards for you reference:

[EVAL-ADIN6310T1LEBZ ADIN6310 Field Switch Reference Design | Analog Devices|https://www.analog.com/en/resources/evaluation-hardware-and-software/evaluation-boards-kits/eval-adin6310t1lebz.html]

[DEMO-ADIN1100D2Z Evaluation Board | Analog Devices|https://www.analog.com/en/resources/evaluation-hardware-and-software/evaluation-boards-kits/demo-adin1100d2z.html]

Kind Regards

Olivier

Dear folivier,

Thank you for your reply and the information provided.

I would like to seek a clarification ; It is mentioned in the evaluation board that the LT8440 shunts current even under no-load conditions to maintain a minimum input current of 20 mA during normal operation.

Could you please confirm whether this requirement is only on the field device or do we need to consider this in the APL switch (Powered Spur port) as well.

Thanks

Chaitanya

Hi Chaitanya23 ,

The 20mA current draw requirement is only for the field device side. For the APL switch side, it has to be able to supply this current to the field device. Please refer to the APL specifications for the these minimum current values.

The LT8440 help to make sure that 20mA is always drawn, even if the "real" load requires less current

Kind Regards

Olivier

Dear folivier,

Thanks for the information .

1. In continuation,I would like to understand whether the LT4356 surge stopper IC and MAX4995A current-limit switch are suitable for use in an Ethernet-APL intrinsic safety barrier (spur port – SPAA/SPBA).

Based on your technical article “Surge Stopper IC Simplifies Design of Intrinsic Safety Barrier for Electronics,” it appears that LT4356 can be used in intrinsic safety applications. However, we have the following concerns:

• Let-through energy during fault conditions
• Suitability for spark ignition protection, especially for Ex ia requirements
• Need for additional external protection components to meet IS certification

Additionally, could you please clarify whether MAX4995A/MAX4995 is appropriate for such applications, considering APL voltage/current levels and intrinsic safety requirements?

2.The LTC4296-1 IC supports classification; however, since classification is not required in our design, is the circuit shown below still necessary, or can it be eliminated?

Your guidance on suitability, limitations, and recommended design approach would be highly appreciated. 

Thanks & Regards

Chaitanya

Dear folivier,

Gentle Remainder! Can reply on this query..

Thanks

chaitanya

Gentle Remainder! We are looking for solution ...Can someone reply with solution