DS17485/DS17487
3V/5V Real-Time Clock
www.maxim-ic.com
FEATURES
PIN ASSIGNMENT
Incorporates industry standard DS1287 PC clock
plus enhanced features:
1
24
23
22
21
20
19
18
17
16
15
14
13
VCC
PWR
X1
SQW
2
3
4
5
6
7
8
9
10
CꢀY2K compliant
VBAUX
X2
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
Cꢀ+3V or +5V operation
RCLR
VBAT
IRQ
KS
CꢀSMI recovery stack
Cꢀ64-bit silicon serial number
CꢀPower-control circuitry supports system
power-on from date/time alarm or key
closure
RD
GND
ALE
11
12
Cꢀ32kHz output on power-up
CꢀCrystal select bit allows RTC to operate with
6pF or 12.5pF crystal
CS
GND
DS17485 24-Pin DIP
DS17485S 24-Pin SO
Cꢀ114 bytes user NV RAM
CꢀAuxiliary battery input
1
24
23
22
21
20
19
18
17
16
15
14
13
VCC
Cꢀ4kB additional NV RAM
CꢀRAM clear input
NC
NC
SQW
2
3
4
5
6
7
8
9
10
VBAUX
CꢀCentury register
RCLR
NC
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
CꢀDate alarm register
IRQ
KS
CꢀCompatible with existing BIOS for original
DS1287 functions
RD
CꢀAvailable as chip (DS17485) or standalone
module with embedded battery and crystal
(DS17487)
NC
ALE
11
12
CS
GND
CꢀTimekeeping algorithm includes leap-year
compensation valid up to 2100
CꢀUnderwriters Laboratory (UL) recognized
DS17487 24-Pin
Encapsulated Package
TYPICAL OPERATING CIRCUIT
IRQ
VBAT
RCLR
VBAUX
SQW
VCC
1
2
28
27
26
25
24
23
22
21
20
19
18
17
16
15
KS
RD
3
GND
WR
4
5
ALE
CS
6
VCC
7
GND
GND
AD7
AD6
NC
PWR
X1
8
9
X2
10
11
12
13
14
NC
ADO
AD1
AD2
AD5
AD4
AD3
DS17485E 28-Pin TSOP
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