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AM335x w/ TLK110

Ryuuichi machida
Guru 12085 points
Other Parts Discussed in Thread: TLK110

Hi,

My customer asked us following question about sysboot[1] of "AM335x_ICE Board".

To begin w/, here are tips about "AM335x_ICE Board".

According to schematic of "AM335x_ICE board",

1. User can select pull up (10kohm) or pull down (100kohm) by setting "J5" connector for sysboot[1].

2. Sysboot[1] connect to both "TX_EN" of TLK110 and "MII1_TXEN" of AM335x.

3. Internal Pull down (From 14.5k to 48.1kohm) is used in "TX_EN" pin.

Here is question.

* According to Datasheet of AM335x, VIH(min) for sysboot[1] is 2V.

However, when worst internal pull down value are used TLK110 and sysboot[1] is connected to pull up by setting "J5" connector, VIH of AM335x does NOT meet.

(Please see following calculation.)

Pull up resistor : 10k

Pull down resistor of TLK110(TX_EN pin) : 14.5k (worst case)

 VAUX2 : 3.3V

Then, input voltage to "MII1_TXEN" pin (sysboot[1] function) = 3.3 x (14.5k / (10k + 14.5k)) = 1.953V

(This does NOT reach 2V(VIH(min)).)

So, could you tell me why you used 10k for pull up resisitor ?

Best Regards,

Machida