DP83867IR: LED_x pin configuration for blinking external LED

Kazuki Kuramochi

Part Number: DP83867IR

Hello team,

Our customer is considering to use DP83867IR.

Then, they'd like to make the circuit which can confirm 100BASE-TX/1000BASE-T link status by external LED using LED_x pin.
Also, they want to use LED_x pin as strap configuration as well.

Then, could you provide suggested circuit for this application using 3.3V power supply for LED and controlling transistor by LED_x pin out put when VDDIO is 1.8V?(It is same as datasheet p55)

Also, below is their configuration.

LEDCR1 and LEDCR2 is default
LED_x pin mode config are as below
1. LED_0 : mode1
2. LED_1 : mode4
3. LED_2 : mode1

If possible, it is really helpful is you provide resistor divider setting which can achieve above setting at DP83867ERGZ EVM users guide's LED_STRAP PINS.

Also, could you please tell me LED_1/2 status(Hi-Z or Lo) when 100/100BT is unlinked?
We understood there is PD but we'd like to know about the output logic circuit status.

Best regards,
Kazuki Kuramochi

over 1 year ago

0 Evan Mayhew over 1 year ago

TI__Mastermind 25378 points

Hi Kuramochi-san,

Please see strapping networks for each pin below:

LED_0: no PU or PD resistors, left open (mode 1)

LED_1: 2.49k PU, no PD (mode 4)

LED_2: no PU or PD resistors, left open (mode 1)

Default LEDCR1 and LEDCR2 is valid to have both 100Base-TX and 1000Base-T link status LEDs.

Please treat the LED pins as high-Z during all link or no link cases.

Thank you,

Evan

0 Kazuki Kuramochi over 1 year ago in reply to Evan Mayhew

TI__Genius 11625 points

Hi Evan,

Thank you for your reply.

We'd like to confirm your suggestion regarding "left open" and "no PD".

Does both mean, is your suggestion connecting LED_x pin to Transistor's base with open pin and pulled-up pin?

Best regards,
Kazuki Kuramochi

+1 Evan Mayhew over 1 year ago in reply to Kazuki Kuramochi

TI__Mastermind 25378 points

Hi Kuramochi-san,

Yes, let me clarify further:

- For LED_1, pin would be connected to a 2.49k PU and the base of the transistor.

- For LED_0 and LED_2, will only be connected to base of transistor.

Thank you,

Evan

0 Kazuki Kuramochi over 1 year ago in reply to Evan Mayhew

TI__Genius 11625 points

Hi Evan,

Sorry for my late reply due to Japan was in holiday season.

We have question for your following answer.

-----
Please treat the LED pins as high-Z during all link or no link cases.
-----

I asked about unliked status's LED pin condition but my understanding for your answer is LED pin is always Hi-z regard less of linked or no kinked.
It mean LED is always on if we control NPN transistor as same as datasheet.
So I suppose LED pin can be low actively during unlinked condition after pin strap latch in.

Could you please confirm pin status during unlinked again just in case?

Best regards,
Kazuki Kuramochi

0 Evan Mayhew over 1 year ago in reply to Kazuki Kuramochi

TI__Mastermind 25378 points

Hi Kuramochi-san

Apologies for the confusion here, I misunderstood LED pin behavior.

LED pin is always driven high or low after power-up, based on interrupt and polarity setting. When the pin is not driven, the pin's internal scheme will not source or sink any current. From this, we treat the non-driven state as high-Z.

Please let me know if I can clarify further.

Thank you,

Evan

0 Kazuki Kuramochi over 1 year ago in reply to Evan Mayhew

TI__Genius 11625 points

Hi Evan-san,

I understand that LED pin during input condition should be treat as Hi-z as like as before latch-in but it will be High or Low once it was configured as output as like as after latch-in.

Best regards,
Kazuki Kuramochi

0 Evan Mayhew over 1 year ago in reply to Kazuki Kuramochi

TI__Mastermind 25378 points

Hi Kuramochi-san,

It will depend on the polarity setting of the LED. For the default case of active high, I expect the LED to be low after latch-in until the LED's interrupt condition is triggered.

The sequence here would be: High-Z (before latch-in) -> Low (after latch-in while interrupt isn't triggered) -> High (during interrupt condition)

Thank you,

Evan

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DP83867IR: LED_x pin configuration for blinking external LED