DS17885/DS17887
3V/5V Real-Time Clock
www.maxim-ic.com
FEATURES
Incorporates industry standard DS1287 PC clock
plus enhanced features:
§
Y2K compliant
§
+3V or +5V operation
§
SMI recovery stack
§
64-bit silicon serial number
§
Power-control circuitry supports system
power-on from date/time alarm or key
closure
§
32kHz output on power-up
§
Crystal select bit allows RTC to operate with
6pF or 12.5pF crystal
§
114 bytes user NV RAM
§
Auxiliary battery input
§
8kB additional NV RAM
§
RAM clear input
§
Century register
§
Date alarm register
§
Compatible with existing BIOS for original
DS1287 functions
§
Available as chip (DS17885) or standalone
module with embedded battery and crystal
(DS17887)
§
Timekeeping algorithm includes leap-year
compensation valid up to 2100
§
Underwriters Laboratory (UL) recognized
PIN ASSIGNMENT
PWR
X1
X2
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
GND
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
VCC
SQW
VBAUX
RCLR
VBAT
IRQ
KS
RD
GND
WR
ALE
CS
DS17885 24-Pin DIP
DS17885S 24-Pin SO
PWR
NC
NC
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
GND
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
VCC
SQW
VBAUX
RCLR
NC
IRQ
KS
RD
NC
WR
ALE
CS
DS17887 24-Pin
Encapsulated Package
TYPICAL OPERATING CIRCUIT
IRQ
VBAT
RCLR
VBAUX
SQW
VCC
VCC
PWR
X1
X2
NC
ADO
AD1
AD2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
KS
RD
GND
WR
ALE
CS
GND
GND
AD7
AD6
NC
AD5
AD4
AD3
DS17885E 28-Pin TSOP
1 of 38
050802
DALLAS [ DALLAS SEMICONDUCTOR ]
