28 Apr
2012
28 Apr
'12
11:57 a.m.
On 2012 Apr 27, at 11:39 AM, Tony Duell wrote:
Yes, but AFAIK it doesn't specify if this supply has to be floating,
centre-tapped to ground, or whatever. That implies to me an isolated
filament heating a separate cathode. So I can't see why AC is
essential.
The datasheet shows only a single connection for Vff, not a floating
connection.
AC is required by the WOM for two reasons:
- Vff is used in a critical area of the chip. DC used here would
[...]
[1] Vff = 6.3V nearly always implies an
indrectly-heated cathode,
so the
polarity and whether it's AC or DC make very little difference.
The datasheet specifies AC.
- The AC is also used as a clock to periodically empty the WOM bit-
[...]
I would think the published Iff - Vff curve i nthe data shert is
incompatible with either of these uses.
-tony