DS14285-DS14287 DALLAS [Dallas Semiconductor], DS14285-DS14287 Datasheet - Page 5

• Manufacturer Part Number: DS14285-DS14287
• Description: Real Time Clock with NV RAM Control
• Manufacturer: DALLAS [Dallas Semiconductor]

In a typical application
and out of power fail without affecting any of the control registers.
RAM.
V
internal switch to power an external RAM.
DS14285 Only
X1, X2 - Connections for a standard 32.768 kHz quartz crystal. The internal oscillator circuitry is
designed for operation with a crystal having a specified load capacitance (CL) of 6 pF. The crystal is
connected directly to the X1 and X2 pins. There is no need for external capacitors or resistors. Note: X1
and X2 are very high impedance nodes. It is recommended that they and the crystal be guard–ringed with
ground and that high frequency signals be kept away from the crystal area. For more information on
crystal selection and crystal layout considerations, please consult Application Note 58, “Crystal
Considerations with Dallas Real Time Clocks.”
V
section for considerations in selecting the size of the external energy source
The battery should be connected directly to the V
battery to the VBAT pin. Furthermore, a diode is not necessary because reverse charging current
protection circuitry is provided internal to the device and has passed the requirements of Underwriters
Laboratories for UL listing.
CEI
CEO
CEO
CEO
CCO
BAT
(External RAM Chip Enable Input, active low) -
will be forced to an inactive level regardless of
will reflect
(External RAM Chip Enable Output, active low) - When V
– Battery input for any standard 3-volt lithium cell or other energy source. See the Power-Up/Down
(External RAM Power Supply Output) - V
CEI
is internally pulled up with a 50k resistor.
CEI
provided the
RESET
can be connected to V
RESET
is at a logic high. When V
BAT
5 of 25
CCO
CEI
CC
pin. A diode must not be placed in series with the
. This connection will allow the DS14287 to go in
.
provides the higher of V
CEI
should be driven low to enable the external
CC
CC
is greater than 4.25 volts (typical),
is less than 4.25 volts (typical),
CC
or V
DS14285/DS14287
BAT
through an