DS1646-120 Maxim Integrated Products, DS1646-120 Datasheet - Page 4

• Manufacturer Part Number: DS1646-120
• Description: Real Time Clock
• Manufacturer: Maxim Integrated Products

Specifications of DS1646-120

• Function: Clock, Calendar, NV Timekeeping RAM
• Rtc Memory Size: 131072 B
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 4.5 V
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Mounting Style: Through Hole
• Rtc Bus Interface: Parallel
• Package / Case: eDIP
• Time Format: HH:MM:SS
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

BLOCK DIAGRAM DS1646 Figure 1
TRUTH TABLE DS1646 Table 1
SETTING THE CLOCK
The MSB Bit, B7, of the control register is the write bit. Setting the write bit to a 1, like the read bit halts
updates to the DS1646 registers. The user can then load them with the correct day, date and time data in
24-hour BCD format. Resetting the write bit to a 0 then transfers those values to the actual clock counters
and allows normal operation to resume.
STOPPING AND STARTING THE CLOCK OSCILLATOR
The clock oscillator may be stopped at any time. To increase the shelf life, the oscillator can be turned off
to minimize current drain from the battery. The
to a 1 stops the oscillator.
FREQUENCY TEST BIT
Bit 6 of the day byte is the frequency test bit. When the frequency test bit is set to logic 1 and
the oscillator is running, the LSB of the second’s register will toggle at 512 Hz. When the seconds
register is being read, the DQ0 line will toggle at the 512 Hz frequency as long as conditions for access
remain valid (i.e.,
<4.5V >V
5V ± 10%
<V
V
CC
BAT
BAT
CE
low,
V
V
V
V
CE
X
X
X
OE
IH
IL
IL
IL
low, and address for seconds register remain valid and stable).
V
V
OE
X
X
X
X
X
IL
IH
WE
V
V
V
X
X
X
X
IH
IH
IL
OSC
4 of 12
DESELECT
DESELECT
DESELECT
DESELECT
WRITE
MODE
bit is the MSB for the second’s registers. Setting it
READ
READ
DATA OUT
DATA IN
HIGH-Z
HIGH-Z
HIGH-Z
HIGH-Z
HIGH-Z
DQ
DATA RETENTION
CMOS STANDBY
STANDBY
STANDBY
POWER
ACTIVE
ACTIVE
ACTIVE
MODE
DS1646/DS1646P