DS1284QN+ Maxim Integrated Products, DS1284QN+ Datasheet - Page 5

• Manufacturer Part Number: DS1284QN+
• Description: IC TIMEKEEPER WATCHDG IND 28PLCC
• Manufacturer: Maxim Integrated Products
• Type: Watchdog Timerr

Specifications of DS1284QN+

• Memory Size: 50B
• Time Format: HH:MM:SS:hh (12/24 hr)
• Date Format: YY-MM-DD-dd
• Interface: Parallel
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-LCC, 28-PLCC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

DS1284/DS1286
HUNDREDTHS-OF-SECONDS GENERATOR
The hundredths-of-seconds generator circuit shown in the Block Diagram (Figure 1) is a state machine
that divides the incoming frequency (4096Hz) by 41 for 24 cycles and 40 for 1 cycle. This produces a
100Hz output that is slightly off during the short term, and is exactly correct every 250ms. The divide
ratio is given by:
Ratio = [41 x 24 + 40 x 1] / 25 = 40.96
Thus, the long-term average frequency output is exactly 100Hz.
Figure 2. Watchdog Timekeeper Registers
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