DS14285-DS14287 DALLAS [Dallas Semiconductor], DS14285-DS14287 Datasheet - Page 2

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

ORDERING INFORMATION
DS14285
DS14285N
DS14285S
DS14285SN
DS14285Q
DS14285QN
DS14287
PIN DESCRIPTION
AD0-AD7
NC
MOT
AS
R/
DS
SQW
V
GND
V
X1, X2
V
DESCRIPTION
The DS14285/DS14287 Real Time Clock with NVRAM Control provides the industry standard DS1287
clock function with the additional feature of providing nonvolatile control for an external SRAM.
Functions include a nonvolatile time-of-day clock, alarm, 100-year calendar, programmable interrupt,
square wave generator, and 114 bytes of nonvolatile static RAM. For the DS14287 a lithium energy
source, quartz crystal, and write protection circuitry are contained within a 24-pin dual in-line package.
The DS14285 requires an external quartz crystal connected to the X1 and X2 pins as well as an external
energy source connected to the V
to the DS14285 via pins 1 and 2 (X1, X2). The crystal selected for use should have a specified load
capacitance (C
please consult Application Note 58, “Crystal Considerations with Dallas Real-time Clocks.”
The DS14285/DS14287 uses its backup energy source and battery-backup controller to make a standard
CMOS static RAM nonvolatile during power-fail conditions. During power fail, the DS14285/DS14287
automatically write-protects the external SRAM and provides a V
battery.
CS
RESET
IRQ
CEI
CEO
CC
CCO
BAT
W
- Multiplexed Address/Data Bus
- No Connection
- Bus Type Select (DS14285Q only)
- Chip Select
- Address Strobe
- Read/Write Input
- Data Strobe
- Reset Input
- Interrupt Request Output
- Square Wave Output
- +5V Supply
- Ground
- RAM Power Supply Output
- RAM Chip Enable In
- RAM Chip Enable Out
- 32.768 kHz Crystal Connections
- +3V Battery Input
L
) of 6 pF. For more information on crystal selection and crystal layout considerations,
RTC Chip; 24-pin DIP
RTC Chip; 24-pin DIP; Industrial Temp Range
RTC Chip; 24-pin SOIC
RTC Chip; 24-pin SOIC; Industrial Temp Range
RTC Chip; 28-pin PLCC
RTC Chip; 28-pin PLCC; Industrial Temp Range
RTC Module; 24-pin DIP
BAT
pin. A standard 32.768 kHz quartz crystal can be directly connected
2 of 25
CC
output sourced from its internal
DS14285/DS14287