DS14285SN Maxim Integrated Products, DS14285SN Datasheet - Page 7

• Manufacturer Part Number: DS14285SN
• Description: IC RTC W/NV RAM CNTRL IND 24SOIC
• Manufacturer: Maxim Integrated Products
• Type: Clock/Calendar/NVSRAMr

Specifications of DS14285SN

• Memory Size: 114B
• Time Format: HH:MM:SS (12/24 hr)
• Date Format: YY-MM-DD-dd
• Interface: Parallel
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

POWER-DOWN/POWER-UP CONSIDERATIONS
The real time clock function will continue to operate and all of the RAM, time, calendar, and alarm
memory locations remain nonvolatile regardless of the level of the V
DS14285/DS14287 and reaches a level of greater than 4.25 volts (typical), the device becomes accessible
after 200 ms, provided that the oscillator is running and the oscillator countdown chain is not in reset (see
Register A). This time period allows the system to stabilize after power is applied. When V
4.25 volts (typical), the chip select input is internally forced to an inactive level regardless of the value of
is in a write-protected state, all inputs are ignored and all outputs are in a high impedance state. When
V
lithium energy source supplies power to the Real-time Clock and the RAM memory.
An external SRAM can be made nonvolatile by using the V
1). Nonvolatile control of the external SRAM is analogous to that of the real time clock registers. When
V
protection occurs when V
During power up, when V
after 200 ms. During power-valid operation, the
propagation delay of less than 10 ns.
When V
V
internal lithium cell through the V
powered by V
When the device is in battery backup mode, the energy source connected to the V
the DS14285, or the internal lithium cell in the case of the DS14287 can power an external SRAM for an
extended period of time. The amount of time that the lithium cell can supply power to the external SRAM
is a function of the data retention current of the SRAM. The capacity of the lithium cell that is
encapsulated within the DS14287 module is 130 mAh. If an SRAM with a data retention current of less
than 1 µA is used and the oscillator current is 300 nA (typical), the cumulative data retention time is
calculated at more than 11 years.
CS
CC
CC
CCO
at the input pin. The DS14285/DS14287 is, therefore, write-protected. When the DS14285/DS14287
falls below a level of approximately 3 volts, the external V
slews down during a power fail,
pin. When V
CC
is above a level of approximately 3V, the external SRAM will be powered by V
CC
or the internal lithium cell.
CC
is below a level of approximately 3V, the external SRAM will be powered by the
CC
CC
is less than 4.25 volts (typical).
reaches a level of greater than 4.25 volts (typical),
CCO
pin. An internal comparator and switch determine whether V
CEO
is driven to an inactive level regardless
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CEI
input is passed to the
CCO
CC
and SRAM chip enable pins (see Figure
supply is switched off and an internal
CC
input. When V
BAT
CEO
CEO
CC
pin in the case of
CEI
will reflect
is applied to the
output with a
CC
CC
. This write
through the
falls below
CCO
CEI
is