
DS1688/DS1691
PIN DESCRIPTION
PIN
SO
EDIP
NAME
FUNCTION
1
VBAUX
Auxiliary Battery Supply
2, 3
—
X1, X2
Crystal Input, Crystal Output
4
RCLR
Active-Low RAM Clear Input
5–12
AD0–AD7
Muxed Address/Data Bus
13
PWR
Active-Low Power-On Interrupt Output
14, 19
14
GND
Ground
15
KS
Active-Low Kickstart Input
16
CS
Active-Low Chip Select Input
17
ALE
Address Strobe
18
WR
Active-Low Write Data Strobe
20
RD
Active-Low Read Data Strobe
21
PSEL
+3V or +5V Power Select
22
IRQ
Active-Low Interrupt Request Output
23
—
VBAT
Battery + Supply
24
SQW
Square-Wave Output. This signal functions identical to the
DS1689/DS1693 with an exception occurring at power-up. A
32kHz square wave is output on this pin, tREC, after a power-up
condition has been detected. This condition sets the following
bits, enabling the 32kHz output: DV1 = 1, SQWE = 1, and E32K
= 1. The square wave is output on this pin if either SQWE = 1 or
E32K = 1.
25
VCCO
RAM Power-Supply Output
26
VCCI
+3V or +5V Main Supply
27
CEO
Active-Low RAM Chip Enable Out
28
CEI
Active-Low RAM Chip Enable In
—
2, 3, 19,
23
N.C.
No Connection
PACKAGE INFORMATION
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
28 SO
F28+3
28 PDIP
P28-6
28 EDIP
MDP28-2
3 of 3
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M a x i m In tegra t ed P r oduc ts , 1 2 0 S a n Ga brie l D r iv e , Sun ny vale , CA 94 086 40 8 - 7 3 7 - 76 00
2005 Maxim Integrated Products
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