Hello,
I'm working on a proven hardware design with FM25V20A. The design has previously been proven working with CY15B104Q 4Mb FRAM device and the application code has been verified as working.
The pull-up on FM25V20A pin 7 has been removed as the Rev I (Aug 2019) Datasheet for FM25V20A states this pin is "DNU" and can be left floating or pulled-up (FM25M20A DS Rev I, page 3).
However a previous revision of the FM25V20A datasheet, Rev D (2014), indicates pin 7 is #HOLD and must be pulled-up when unused.
When pin 7 "DNU" is floating, the application can not access the FRAM device. When pin 7 DNU is pulled up, the application can access the FRAM device correctly. The application does not implement control of #HOLD function on the SPI interface, the SPI interface does not connect to pin 7 in any way.
It appears the DNU pin 7 is actually functioning as a #HOLD pin described in Rev D of the datasheet and not as DNU described in Rev I.
The part marking is:
G2V20A
615552
2019
<square> C
This should indicate the part is from Lot# 615552 and was packaged week 19 of 2020?
I expected the part to behave as the Rev I of the FM25V20A datasheet describes, however, it does not. It looks that the DNU pin MUST be pulled-up - there is no option to leave floating as the datasheet states.
Measuring the voltage at the floating DNU pin reads 0v, no noise or ripple. The oscilloscope is calibrated , 500MHz voltage probe used with a local PCB ground connection.
Is there a documentation error or a fault with the part?
