Holtek HT8972. A different PT2399?

[anotherjim]

Forgive me if this is commonly known, but I just saw this chip mentioned over in Muffwiggler forums.
The Datasheet...
www.holtek.com.tw/documents/10179/116711/8972v100.pdf
Seem a lot like the PT2399.
Note the timing resistor chart doesn't go lower than 2.8k @22Mhz = 30mS. The Princeton version suggests 500R for that delay.
So, has anybody tried one?

[Mark Hammer]

I hadn't known of this chip before you raised it here.  The datasheet is dated 2008, while the Princeton datasheets I have are dated 2000, and the HT8955 is dated May 1998, so it is quite possible that Holtek is making a copycat, or even that Princeton simply sold the die/license to Holtek.  But whatever the case, you are quite right that the two chips are very very similar.

I guess what I'd want to know is what the A/D format is and resolution is.  I was given to understand that the 2399 uses delta modulation, whereby the modest 10-bitresolution was applied to the moment to moment change in signal amplitude, and not to the total signal.  The HT8955 uses a 10-bit sample of the entire signal at any given moment in time, which is fine if one aims for limited bandwidth, but not exactly hi-fi.  If one is using 10-bit resolution not to index the amplitude of the entire sample at this moment, but rather simply how different it is from the last sample, that is akin to having greater sample resolution.  BUt agin,that was just my understanding, and may not in fact be true of the 2399.

The 8972 says it has 40k of RAM on board while the 2399 says 44k, though I imagine that makes minimal difference.

I look forward to others having their say here.  How did you find out about this chip? (Duh, you already said so)

[anotherjim]

Yeh, it's in the Velleman "DIGITAL ECHO CHAMBER" kit, which is a general "toy" project with onboard electret mic & LM386 for a speaker.
http://www.velleman.co.uk/contents/en-uk/p109.html
Shouldn't be hard to get one to play with.
I can't find any mention of minimum timing resistor value in Holteks data.

If it is compatible with the PT2399 and can go faster without locking up, it could be a very important chip.