fm3808 Ramtron Corporation, fm3808 Datasheet - Page 25

• Manufacturer Part Number: fm3808
• Description: 256kb Bytewide Fram W/ Real-time Clock
• Manufacturer: Ramtron Corporation

The backup power supply V
cycled on and off, the current drain on the battery is guaranteed to be < I
there is no backup current drawn from the battery.
It is not recommended that V
what happens if this occurs. The drawing shows the behavior of the INT at power-up first without a backup
supply V
with the Power Fail bit enabled (PFE=1) and the INT pin will be active low (open drain) and pulse output mode
(P/L=1). The Interrupt register 7FF6h defaults to the value 24h. Once V
may be written to a different value to change the behavior of the INT pin. When a battery is used as a backup
source, V
battery is inserted, the current drain on the battery is guaranteed to be I
Rev. 1.3 (EOL)
Feb. 2006
Register
7FF6
INT
V
BAK
DD
DD
must be applied prior to inserting the battery to prevent battery drain. Once V
then with a backup supply. On power-up without a backup power supply, the device will initialize
V
I
BAK
BAK
hi-Z
V
RST
> I
BAK
V
BAK
TP
24h
DD
must be applied prior to V
(max)
power be applied before V
V
DD
Recommended Power Up Sequence
V
(~ 200 ms)
BAK
INT pin Timing at Power Up
t
IPU
I
BAK
= 0
New value written (register is battery backed)
DD
BAK
power up. Once a battery is inserted and V
, however the timing diagram above illustrates
< I
BAK
BAK
driven low
BAK
(max).
(max)
DD
(max). When V
is established, the register 7FF6h
I
DD
BAK
DD
power is applied,
= 0
is applied and a
V
TP
t
IPU
Page 25 of 27
DD
FM3808
is