DS1688 Datasheet, PDF (1/5 Pages) Dallas Semiconductor – 3 Volt/5 Volt Serialized Real Time Clock with NV RAM Control

DS1688/DS1691
DS1688/DS1691
3 Volt/5 Volt Serialized Real Time Clock
with NV RAM Control
FEATURES
Incorporates industry standard DS1287 PC clock plus
enhanced features:
• +3 or +5 volt operation
• 64–bit Silicon serial number
• 64–bit customer specific ROM or additional serial
number available
• Power control circuitry supports system power on
from date/time alarm or key closure
• Automatic battery backup and write protection to
external SRAM
• Crystal select bit allows RTC to operate with 6 pF or
12.5 pF crystal
• 114 bytes user NVRAM
• Auxiliary battery input
• RAM clear input
• Century register
• 32 KHz output for power management
• 32–bit V_CC powered elapsed time counter
• 32–bit V_BAT powered elapsed time counter
• 16–bit power cycle counter
• Compatible with existing BIOS for original DS1287
functions
• Available as chip (DS1688) or stand–alone module
with embedded battery and crystal (DS1691)
• Timekeeping algorithm includes leap year compensa-
tion valid up to 2100
ORDERING INFORMATION
PART #
DS1688
DS1688S
DS1691
DESCRIPTION
RTC Chip, 28–pin DIP
RTC Chip, 28–pin SOIC
RTC Module; 28–pin DIP
PIN ASSIGNMENT
V_BAUX 1
X1 2
X2 3
RCLR 4
AD0 5
AD1 6
AD2 7
AD3 8
AD4 9
AD5 10
AD6 11
AD7 12
PWR 13
GND 14
28 CEI
27 CEO
26 V_CCI
25 V_CCO
24 SQW
23 V_BAT
22 IRQ
21 PSEL
20 RD
19 GND
18 WR
17 ALE
16 CS
15 KS
DS1688 28–PIN DIP
(600 MIL)
V_BAUX 1
NC 2
NC 3
RCLR 4
AD0 5
AD1 6
AD2 7
AD3 8
AD4 9
AD5 10
AD6 11
AD7 12
PWR 13
GND 14
V_BAUX
X1
X2
RCLR
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
PWR
GND
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
28
CEI
2
27
CEO
3
26
V_CCI
4
25
V_CCO
5
24
SQW
6
23
V_BAT
7
22
IRQ
8
21
PSEL
9
20
RD
10
19
GND
11
18
WR
12
17
ALE
13
16
CS
14
15
KS
DS1688S 28–PIN SOIC
(330 MIL)
CEI
CEO
V_CCI
V_CCO
SQW
NC
IRQ
PSEL
RD
NC
WR
ALE
CS
KS
DS1691 28–PIN ENCAPSU-
LATED PACKAGE (740 MIL)
PIN DESCRIPTION
X1
– Crystal Input
X2
– Crystal Output
RCLR
– RAM Clear Input
AD0-AD7
– Mux’ed Address/Data Bus
PWR
– Power–on Interrupt Output
KS
– Kickstart Input
CS
– RTC Chip Select Input
ALE
– RTC Address Strobe
WR
– RTC Write Data Strobe
RD
– RTC Read Data Strobe
V_CCO
– RAM Power Supply Output
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