I am running my ATtiny85 with an external 32.768 kHz crystal because I need to keep accurate time. I also need to use the ADC in my application. However, the datasheet specifies that the minimum ADC frequency is 50 kHz. Furthermore, the minimum divisor for the ADC prescaler is 2, so the effective clock to the ADC would end up being 16.384 kHz.
Now, I have tested this with the mentioned 32.768 kHz crystal, and the ADC seems to work. I am getting good enough results. However, is what I am doing "allowed" or am I setting myself up for failing big-time? The plan is that if this device is something people want, I would make maybe 100 of them, and it would suck if I assume this would work when in fact there might be a problem later.
Does anyone have any wise words?