Hello~
One of my customer is making the NVR products, and He meets the problem that can not be understood.
The customer is using to TPS2384 with Alteranative A & Automode (MS pin = '0').
And, additionally, AC_LO pin is connected directly to drive the ALT_A/B pin.
Test environments, conditions & situations of the customer are as below.
1. Turn the power OFF the NVR system.
2. It is connected between NVR's PSE port and PD (IP-Camera) via Ethernet cable.
3. Turn the power ON the NVR.
4. ALT_A/B pin is '0'.
5. No communication between Host and TPS2384 by I2C.
6. TPS2384 is supply the power to PD, normally. Below is the waveform of N-pin at this time.
7. While NVR's power is ON, user remove the Ethernet cable from PD.
8. User re-insert the cable.
9. But, TPS2384 is NOT supply the power to PD. Below is the waveform of N-pin at this time.
10. Through the I2C communication, the Host is control the TPS2384, and the AC_LO pin is set to '1'.
11. ALT_A/B pin also is set to '1', because AC_LO pin is connected to the ALT_A/B pin.
12. After Back-off time (2 seconds), TPS2384 is re-supply the power to PD, normally. Below is the waveform of N-pin at this time.
13. He claims to use the IEEE compliant PDs, but it was not confirmed yet.
14. In case of Other vendor's IP-Camera (It means another vendor's PD), it does not happen this kind of behavior. TPS2384 is always supply the power to the PD even if user removes the Ethernet cable and re-inserts the Ethernet cable, while NVR's power is ON.
He wants to know Why does it do this kind of behavior?
Thanks... C.W. :)