Re: a few hp42s and 42s emulator questions Message #4 Posted by Lyuka on 16 Jan 2008, 11:01 p.m., in response to message #3 by Eric Smith
Do NOT use CY62256VNLL-70SNXI without special care (more modification needed).
VN suffix means low voltage (2.7-3.6V) version, and its absolute
maximum rating of the supply voltage is +4.6V.
The voltage of fresh 3xSR44 often exceeds 4.7V,
it may causes the latchup of the devices and may result in severe destruction.
The following (cypress's) devices are recommended.
CY62256LL-70SNC (4.5-5.5V, Low power, 70ns, SNC28-300mil, Commercial)
CY62256LL-70SNI (4.5-5.5V, Low power, 70ns, SNC28-300mil, Industrial)
CY62256LL-70SNXC (4.5-5.5V, Low power, 70ns, SNC28-300mil, Pb free, Commercial)
CY62256LL-70SNXI (4.5-5.5V, Low power, 70ns, SNC28-300mil, Pb free, Industrial)
And also these faster 55ns devices shown below can be used, however, It may be needed some capacitors for power supply decoupling, and series resistors for write and chip select signal dumping, for stable operation.
CY62256LL-55SNC (4.5-5.5V, Low power, 55ns, SNC28-300mil, Commercial)
CY62256LL-55SNI (4.5-5.5V, Low power, 55ns, SNC28-300mil, Industrial)
CY62256LL-55SNXC (4.5-5.5V, Low power, 55ns, SNC28-300mil, Pb free, Commercial)
CY62256LL-55SNXI (4.5-5.5V, Low power, 55ns, SNC28-300mil, Pb free, Industrial)
For more information,
please take a look on my photographical document
"HP-42s upgrade".
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