FM3164-STR Ramtron, FM3164-STR Datasheet - Page 7

• Manufacturer Part Number: FM3164-STR
• Description: case, leaded, supervisor, reflow, soic, supply, process, max, ram, Interface ICs, package, compatible, voltage, memor...
• Manufacturer: Ramtron

to be loaded into the timekeeper core. W is used for
writing new time values. Users should be certain not
to load invalid values, such as FFh, to the
timekeeping registers. Updates to the timekeeping
core occur continuously except when locked.
Backup Power
The real-time clock/calendar is intended to be
permanently powered. When the primary system
power fails, the voltage on the V
When V
will switch to the backup power supply on V
clock operates at extremely low current in order to
maximize battery or capacitor life. However, an
advantage of combining a clock function with FRAM
memory is that data is not lost regardless of the
backup power source.
When inserting a battery into a system board,
higher-than-normal battery drain may occur. It is
recommended
procedure complies with one of the following:
Scenario #1
Scenario #2
Rev. 2.3
Oct. 2006
a) Apply Vdd to board.
b) Insert battery. At this point, I
c) When V
a) Insert battery without power to board (V
b) Apply V
CF
will be less than 1µA.
off). At this point, the I
much higher than the 1µA spec limit. An
extended period of time (days) in this state
could significantly reduce battery life.
DD
is less 2.5V the RTC (and event counters)
DD
DD
Years
8 bits
is powered down, the I
to board. I
that
32.768 kHz
your
BAK
crystal
Months
5 bits
BAK
goes to zero.
Figure 7. Real-Time Clock Core Block Diagram
system
DD
current may be
BAK
pin will drop.
is zero.
BAK
power-up
BAK
current
User Interface Registers
. The
DD
6 bits
Date
3 bits
Days
is
Oscillator
/OSCEN
Trickle Charger
To facilitate capacitor backup the V
optionally provide a trickle charge current. When the
VBC bit, register 0Bh bit 2, is set to 1 the V
will source approximately 15 µA until V
V
charges the capacitor to V
diode and resistor charger. In 5V systems, it provides
the same convenience and also prevents the user from
exceeding the V
In the case where no battery is used, the V
should be tied according to the following conditions:
Although V
recommended if the companion is used. None of the
companion functions will operate below about 2.5V.
! ! ! !
the VBC bit to 0 to prevent battery charging. The
V
resistor as a safety element.
BAK
DD
c) When V
Note: systems using lithium batteries should clear
will be less than 1µA.
Hours
6 bits
or 3.75V whichever is less. In 3V systems, this
For 3.3V systems, V
This assumes V
For 5V systems, attach a 1 µF capacitor to V
and turn the trickle charger on. The V
will charge to the internal backup voltage which
regulates itself to about 3.6V. V
be tied to 5V since the V
will be exceeded. A 1 µF capacitor will keep
the companion functions working for about 1.5
second.
circuitry includes an internal 1 K
BAK
DD
Divider
Clock
BAK
may be connected to V
is powered down, the I
Minutes
maximum voltage specification.
7 bits
DD
512 Hz
does not exceed 3.75V.
BAK
1 Hz
DD
BAK
should be tied to V
without an external
FM3104/16/64/256
(max) specification
Seconds
Update
Logic
7 bits
BAK
W
SS
BAK
BAK
BAK
, this is not
should not
Page 7 of 25
pin can
current
BAK
BAK
BAK
reaches
series
R
BAK
pin
pin
pin
DD
.