FM31274-G Ramtron, FM31274-G Datasheet - Page 7

• Manufacturer Part Number: FM31274-G
• Description: FRAM, MPU SUPPORT, 16K, RTC, SOIC14
• Manufacturer: Ramtron

Specifications of FM31274-G

• Memory Size: 16Kbit
• Nvram Features: RTC
• Supply Voltage Range: 4V To 5.5V
• Memory Case Style: SOIC
• No. Of Pins: 14
• Operating Temperature Range: -40°C To +85°C
• Interface: Serial
• Package / Case: SOIC
• Memory Configuration: 2048 X 8
• Interface Type: I2C, Serial, 2-Wire
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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, one of
the advantages of combining a clock function with
the F-RAM memory is that data is not lost regardless
of the backup power source.
The I
(see DC parametric table). The following graph
shows I
useful for calculating backup time when a capacitor
is used as the V
The minimum V
temperature. The user can expect the minimum V
voltage to be 1.23V at +85°C and 1.90V at -40°C.
The tested limit is 1.55V at +25°C. The minimum
V
+85°C but is not 100% tested.
Rev. 2.0
Jan. 2011
BAK
BAK
voltage has been characterized at -40°C and
Figure 8. V
BAK
DD
current varies with temperature and voltage
Figure 7. I
is less 2.5V the RTC (and event counters)
as a function of V
BAK
BAK
BAK
source.
BAK
(min.) vs. Temperature
voltage varies linearly with
vs. V
BAK
BAK
. These curves are
Voltage
DD
pin will drop.
BAK
. The
BAK
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 80 µA until V
V
external diode and resistor charger. There is a Fast
Charge mode which is enabled by the FC bit (register
0Bh, bit 5). In this mode the trickle charger current is
set to approximately 1 mA, allowing a large backup
capacitor to charge more quickly.
In the case where no backup supply is used, the V
pin should be tied to V
trickle charger (VBC=0), otherwise charger current
will be shunted to ground from V
the VBC bit to 0 to prevent battery charging. The
V
resistor as a safety element. The trickle charger is UL
Recognized.
FM31L278/L276/L274/L272 - 3V I2C Companion
BAK
DD
Note: systems using lithium batteries should clear
. This charges the capacitor to V
circuitry includes an internal 1 K
SS
. Be sure to turn off the
DD
.
DD
BAK
BAK
without an
Page 7 of 26
Ω
pin can
reaches
BAK
series
BAK
pin