MXD1210ESA MAXIM [Maxim Integrated Products], MXD1210ESA Datasheet - Page 5

• Manufacturer Part Number: MXD1210ESA
• Description: Nonvolatile RAM Controller
• Manufacturer: MAXIM [Maxim Integrated Products]

The MXD1210 executes five main functions to perform
reliable RAM operation and battery backup (see
Typical Operating Circuit and Figure 1):
______________ Detailed Description
1. RAM Power-Supply Switch: The switch directs
2. Power-Failure Detection: The write-protection func-
3. Write Protection: This holds the chip-enable output
4. Battery Redundancy: A second battery is optional.
power to the RAM from the incoming supply or
from the selected battery, whichever is at the
greater voltage. The switch control uses the same
criterion to direct power to MXD1210 internal
circuitry.
tion is enabled when a power failure is detected.
The power-failure detection range depends on the
state of the TOL pin as follows:
Power-failure detection is independent of the battery-
backup function and precedes it sequentially as the
power-supply voltage drops during a typical power
failure.
(CEO) to within 0.2V of V
tery, whichever is greater. If the chip-enable input
(CE )is low (active) when power failure is detected,
then CEO is held low until CE is brought high, at
which time CEO is gated high for the duration of
the power failure. The preceding sequence com-
pletes the current RD/WR cycle, preventing data
corruption if the RAM access is a WR cycle.
When two batteries are connected, the stronger
battery is selected to provide RAM backup and to
power the MXD1210. The battery-selection circuitry
remains active while in the battery-backup mode,
selecting the stronger battery and isolating the
weaker one. The battery-selection activity is trans-
parent to the user and the system. If only one bat-
tery is connected, the second battery input should
be grounded.
CONDITION
TOL = V
TOL = GND
CCO
_______________________________________________________________________________________
CCI
or of the selected bat-
V
CCTP
Main Functions
4.75 to 4.50
4.50 to 4.25
RANGE (V)
Nonvolatile RAM Controller
First access: read memory location n, loc(n) = x
Second access: write memory location n,
Third access: read memory location n, loc (n) = ?
If the third access (read) is complement (x), then the
battery is good; otherwise, the battery is not good.
Return to loc(n) = x following the test sequence.
The freshness-seal mode relates to battery longevity
during storage rather than directly to battery backup.
This mode is activated when the first battery is connect-
ed, and is defeated when the voltage at V
exceeds V
teries are isolated from the system; that is, no current is
drained from either battery, and the RAM is not pow-
ered by either battery. This means that batteries can be
installed and the system can be held in inventory with-
out battery discharge. The positive edge rate at
VBATT1 and VBATT2 should exceed 0.1V/ s. The bat-
teries will maintain their full shelf-life while installed in
the system.
The Typical Operating Circuit shows the MXD1210 con-
nected in order to write protect the RAM when V
less than 4.75V, and to provide battery backup to the
supply.
5. Battery-Status Warning: This notifies the system
when the stronger of the two batteries measures
(V
battery voltage is measured. If the battery in use is
low, following the MXD1210 recovery period, the
device issues a warning to the system by inhibit-
ing the second memory cycle. The sequence is as
follows:
2.0V. Each time the MXD1210 is repowered
CCI
loc (n) = complement (x)
CCTP
> V
CCTP
. In the freshness-seal mode, both bat-
) after detecting a power failure, the
Freshness-Seal Mode
Battery Backup
CCI
CC
first
is
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