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Maxim > Design Support > Technical Documents > Application Notes > Real-Time Clocks > APP 5329
Keywords: accurate RTCs, MEMs, I²C, communications, dual power supplies, single supply, timekeeping,
RTC, freshness seal, V
BAT
, battery, batteries, dual-supply, real time clock
APPLICATION NOTE 5329
Implementing Flawless Designs with Accurate I²C
Real-Time Clocks
Apr 20, 2012
Abstract: This application note presents an overview of the operational characteristics of accurate I²C
real-time clocks (RTCs), including the DS3231, DS3231M, and DS3232. It focuses on general
application guidelines that facilitate use of device resources for power management, I²C communication
circuit configurations, and I²C characteristics relative to device power-up sequences and initializations.
Additional discussions on decoupling are provided to support developing strategies for mitigating power-
supply pushing of device frequency.
Introduction
Over the years, I²C communications has become a reoccurring theme in customers' questions about
accurate real-time clocks (RTCs). This includes basic subjects such as circuit setup and operation, and
managing communications to all devices on the I²C port. In many instances, several key decisions need
to be made prior to implementing circuit and firmware designs. This application note provides a basic
operational overview of the characteristics of the accurate RTC, so hardware/firmware engineers can
decide how to effectively manage accurate RTC resources.
Key Operational Characteristics of the I²C Port in Accurate RTCs
Maxim's accurate RTCs have dual power supplies. As shown in Figure 1, three power-supply
configurations can be implemented, depending on the application and desired use condition. The intent of
these supplies is to offer managed, low-current power switching between primary power sources, and
backup power sources such as batteries or supercapacitors.
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