Hi,

I’m having a power consumption issue with a binary counter.
I’m using TI’s SN74LV8154 32 bit binary counter; you may find the data sheet attached. Here's a schematic:



I’m supplying the counter with 2.08V, which should account for the current draw of a few µA (see page 5). Instead I’m drawing 2mA. The counter is fed with a 20MHz pulse; counter outputs nothing (GAL-GBU are pulled to 3.3V).
Where do 2mA come from? How do I drop it into the µA range? Many thanks in advance, I could really use some help here. I attached a pic of the setup too.

Some observations:
It looks like the current draw linearly depends on the input pulse; I don’t remember the exact readings, but I think I had ~0.2mA for 2MHz, ~0.45mA for 4MHz, ~0.6mA for 6MHz.
If I leave GAL-GBU disconnected, the current draw goes to 2.5mA. Same thing if I’m outputting any of the bytes. It’s not because I’m giving a 3.3V input into GAL-GBU, is it? (I don’t have direct access to the circuit right now to check if it is the problem)

 

The power is indeed proportional to the clock frequency as shown in this clip from the data sheet (page 7):

Thus for a 20MHz clock, the current is 20MHz ×56pF×2V = 2.24mA, close to what you measured.
Don't see any way to reduce that current.

 

The power is indeed proportional to the clock frequency as shown in this clip from the data sheet (page 7):
View attachment 145048
Thus for a 20MHz clock, the current is 20MHz ×56pF×2V = 2.24mA, close to what you measured.
Don't see any way to reduce that current.

aha, I see. thank you, that clears it up! Am I right that this is an internal 56pF capacitor?

 

aha, I see. thank you, that clears it up! Am I right that this is an internal 56pF capacitor?

Basically yes. But it's not deliberately added.
It is the distributed equivalent circuit capacitance of all the nodes in the circuit that switch with the clock.
It's inherent to the circuit transistors and the stray capacitance of the interconnects.