TLK111 pins

Hi,

I have moved your post to the Ethernet forum so that it gets visibility from the Ethernet team.

Patrick

Hi Naji,

I will review this today and get back to you soon.

Regards,

Ross

Hi Naji,

I am currently waiting for conformation to question #1 and #3 but I do have answers for your other questions. Please see below. 

Also, please look at page 8 in the TLK111 datasheet in section 3.1. There you will find information about strapping, which is used for our products. Strapping allows the user to put the device in various states depending on the initial startup logic level set by either internal/external pull-ups or pull-downs.

1. Does CLKOUT (pin 25) need to be terminated in any way to avoid emission problems?  It is a 25MHz clock

2. Is 4.87k critical for RBIAS (pin 24)?  Will 4.75k or 4.99k work?

RBIAS 4.87kΩ is a very critical value for proper operation. It sets the main reference bias for the device. Any other resistance can affect the entire device.

3. How is TX_ER configured for 10/100BT on pin 7?

4. If pin 41 is used for RX_ER, how will Auto-MDX always be enabled?  Do I need a pull-up?

Pin 41 can be used for RX_ER and it is also able to provide Auto-MDIX. This pin has an internal pull-up. During reset, the logic state of this pin is taken. By default, this pin is Auto-MDIX enable unless you add an external 2.2kΩ pull-down resistor.

 5. If pin 39 is used for RX_DV, how will MII operation always be selected? Do I need a pull-up?

 Pin 39 can be used for RX_DV and it is also able to provide MII operation. This is because the pin has an internal pull-down that sets the device into MII operation at reset. If you want to operate in RMII mode you will need an external 2.2kΩ pull-up resistor.

6. If pin 40 is used for CRS, how will it know to use bit 5 of the PHYCR register for setting LED Mode? Do I need a pull-up?

Pin 40 can be used for CRS and also set bit 5 of the PHYCR register on reset. There is an internal pull-up resistor for this pin. When you leave this at the default pull-up state (Logical 1) the LEDs will be configured for Mode 1: LED_LINK (ON for Good Link, OFF for No Link), LED_SPEED (ON in 100Mbps, OFF in 10Mbps), LED_ACT (ON Pulse for Activity, OFF for No Activity). If you want to operate the LEDs in different states, you will need to use an external 2.2kΩ pull-down resistor and use the MDIO interface for PHYCR register access to bit[6].

Hi Naji,

Here are the answers to questions #1,3 below:

1. Does CLKOUT (pin 25) need to be terminated in any way to avoid emission problems? It is a 25MHz clock

No, we usually leave this pin unconnected if not required. What type of EMI/EMC concerns or tests do you have planned?

3. How is TX_ER configured for 10/100BT on pin 7?

There is no TX_ER pin for TLK111. Please see attached image. 3201.tlk111.pdf

Regards,

Ross

Hi Ross,

I have had EMI issues in the past with a SPI CLK pin that was not being used. When I turned it into a GPIO, the EMI issues went away. I am concerned that I may run into a similar issue with a free-running 25MHz clock on an unused pin.

I did not see a register bit to shut it off. Would it help if I add a 0.1uF cap on it or will that make it worse?

Thank you

Hi Naji,

What types of EMI compliance tests are you planning on running/ran before? Typically the pin (when not used) can be left unconnected without issue.

Regards,

Ross