Hello,
We are using the TLK100 device in many designs, but in one of our new designs we have found a problem. We are now interfacing the TLK100 with a Marvell 88E6176 gigabit switch with MII interface. For the 88E6176 the TXD0-3 pins are boot strap pins, so for proper operation we had to strap these pins in the following way: TXD0 and TXD2: 4.7k to ground, TXD1 and TXD3: 4.7k to 3.3V.
The problem is that with the following configuration, the TLK100 goes to an unusable state with strange behaviour. E.g. after reset, the PWRDNN/INT pin of the TLK100 goes to low state, if the MDC input is high. (however, both pins should be intputs).
We found out, that the problem is caused by the pull-ups of the TXDx pins, so we made measurements with another design, where the TLK100 is connected to an microcontroller with MII. The result of the measurement was the following (TXDx means a pull-up on the specific TXD pin): if (TXD3)*(TXD1+TXD2)=1, then the TLK100 is unusable.
In the datasheet (latest, rev B) there is no information about any strap configuration of these pins in the Configuration (chapter 3) section, however in the Pin Descriptions (chapter 2) the in the TYPE column for the TXDx pins it is written "IS" which means Input and Configuration. In the "TLK100 External Voltages EVM" user's guide, on page 9 of the schematic there are ignored pull-up and pull-down resistors for TXD1-3, so it seems that there is some strap function on these pins that is not discussed in the TLK100 datasheet.
Can you provide some information about the issue? What are these pins are used for? How to use the TLK100 with a device, that needs strapping of TXD pins?
Thank in advance:
András
