DP83822I: Drive capability of LED_0, LED_1 pins

Takashi Imai

Part Number: DP83822I
Other Parts Discussed in Thread: DP83822EVM

Hello,

Please help to reply customer's questions about the drive capability of the 17pin: LED_0 and 24pin: LED_1 of the DP83822IRHB.

Currently, the customer is designing circuit assuming an output current of approximately 9 mA to light the LED directly from the corresponding pin. (Operating condition: VDDIO = 3.3 V)

In chapter 7.5 Electrical Characteristics of the datasheet, there is description of "I OH/I OL= 4 mA" as the test condition of the output voltage, but we couldn't see the description of the maximum allowable current (absolute maximum rating) of 17pin: LED_0 and 24pin: LED_1.

So, in order to confirm whether the DP83822IRHB can be used, the customer want to know the following 2 points.

1)Is driving a current of approximately 8 mA from the 17pin and the 24pin not a problem in terms of device capability and reliability?

2)If 8mA drive from the each pins is not recommended, what is the "maximum drive current" allowed for the pins?

Thanks & Regards,

T.Imai

2 months ago

0 Takashi Imai 2 months ago

Intellectual 390 points

Hello, since the customer plan to fix the circuit on 5/19 Japan time, they requests a reply within 5/18 of US time. It would highly appreciate it if you help us.

Thank you vey much.

T.Imai

0 Takashi Imai 2 months ago in reply to Takashi Imai

Intellectual 390 points

Hello,

Could someone help me with this?

Thank you very much.

T.Imai

0 Gregory Kobyakov 2 months ago in reply to Takashi Imai

TI__Genius 14480 points

Hi Imai-san,

The maximum current for the LED pins is determined by the output voltage of the pin, which is affected by the current drawn by the application. I can check internally if we have any further guidance beyond the 4mA provided in the datasheet, and will respond tomorrow.

Best regards,

Greg

0 Gregory Kobyakov 2 months ago in reply to Gregory Kobyakov

TI__Genius 14480 points

Hi Imai-san,

If the LED used requires 8mA, this should not effect device capability. We cannot provide the maximum current for the LED pins, but I attached a graph of the LED VOH vs. current load of the DP83826 PHY. The trend for the DP82822 PHY should be similar.

\Best regards,

Greg

0 Takashi Imai 2 months ago in reply to Gregory Kobyakov

Intellectual 390 points

Hi Gregory-san,

Thank you for your support.

I would like to wait for your reply today if the input/output current of LED_0/LED_1 terminal can support 4mA or more and 8mA.

I understood that a graph of the LED VOH vs. current load of the DP83826 you provided is also applicable to DP82822.
From this graph, it seems that the DP83826 (and the DP 82822) is capable of outputting 8 mA although the VOH drops from 3.3 V to about 2.5 V.

Am I correct?

Thanks & Regards,

T.Imai

0 Gregory Kobyakov 2 months ago in reply to Takashi Imai

TI__Genius 14480 points

Hi Imai-san,

Yes, these currents should be supported. However, this also needs to be verified according to the specifications of the LED being used. This LED has been validated on the DP83822EVM:

https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/655/QTLP630-2.pdf

Your understanding is correct. Although the DP83822 LED VOH vs. current load will not be exactly the same as the DP83826, it should follow a similar trend.

Best regards,

Greg

0 Takashi Imai 2 months ago in reply to Gregory Kobyakov

Intellectual 390 points

Hi Gregory-san,

I will tell the customer what you gave me and ask them to check with the LED they use.

After replied to customer, if there are no further questions about this by the end of next week, I will close here.

Best Regards,

T.Imai

+1 Gregory Kobyakov 2 months ago in reply to Takashi Imai

TI__Genius 14480 points

Hi Imai-san,

Thank you for checking.

Best regards,

Greg

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DP83822I: Drive capability of LED_0, LED_1 pins