DS1685S-5 Datasheet Download

Part No.:
DS1685S-5
Download:
Download Datasheet
Description:
[3V/5V Real-Time Clocks]
File Size:
407 K
Page:
33 Pages
Logo:
Manufacturer:
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
PCB Prototype
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DS1685/DS1687 3V/5V Real-Time Clocks
Figure 1. Block Diagram
X1
X2
DS1687 only
16:1 Mux
Divide
by 8
Divide by
64
Divide by
64
OSC
V
CC
GND
V
BAUX
V
BAT
Power
Control
Square
W ave
Generator
IRQ
Generator
SQW
IR Q
PW R
KS
DS1687 only
Registers A, B,C,D
Clock/Calender
Update Logic
CS
RD
WR
ALE
AD0 - AD7
BUS
Interface
Clock/Calendar and
Alarm Registers
Buffered Clock/
Calendar and Alarm
Registers
User Ram
114 Bytes
RAM
Clear
Logic
RLCR
Select
DS1685/DS1687
Extended RAM Addr/
Data Registers
Extended Control/
Status Registers
64-Bit Serial Num ber
Century Counter
Date Alarm
RTC Address -2
RTC Address -3
Extended
User RAM
128 Bytes
OSCILLATOR CIRCUIT
The DS1685 uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or
capacitors to operate. Table 1 specifies several crystal parameters for the external crystal, and Figure 2 shows a
functional schematic of the oscillator circuit. The oscillator is controlled by an enable bit in the control register.
Oscillator startup times are highly dependent upon crystal characteristics, PC board leakage, and layout. High ESR
and excessive capacitive loads are the major contributors to long startup times. A circuit using a crystal with the
recommended characteristics and proper layout usually starts within one second.
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