RTC Power Supply Circuit for System-on-Chip Data Integrity
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Solution Overview
Problem
Newer IC fabrication processes with lower power supply voltage limitations, such as 90 nano-meter CMOS, require a new technique to power real-time clock (RTC) and crystal oscillation circuits in system-on-a-chip (SOC) devices, and there is a risk of data corruption or loss during power down due to the active analog section of the RTC when the battery is connected.
Innovation Solution
A voltage supply circuit that regulates the power supply voltage to 1.0 volts or less, using a reference circuit, start-up circuit, amplifier, and transistors to ensure consistent power to the RTC and oscillation circuit, and a data protection circuit that delays data transfers during power down to prevent corruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the analog section of the RTC is powered from the battery while the digital section is powered from the DC-DC converter, then the RTC can operate during standby, but data can be corrupted or lost during power down
Solution Approach 1:
The patent implements a preliminary action by detecting the power down condition before it occurs and preemptively freezing the RTC counter. The voltage detection circuit identifies when the DC-DC converter is turning off, and before the analog-to-digital transition can cause data corruption, the counter is placed in a frozen state to prevent any incomplete write operations
Solution Approach 2:
The patent applies preliminary anti-action by implementing a mechanism that prevents the harmful effect of data corruption before it can occur. When power down is detected, the system actively freezes the counter operation and prevents any data transfer between analog and digital sections during the critical transition period, thereby counteracting the potential corruption mechanism
2Reliability
If the RTC counter is frozen during power down, then data loss is prevented, but the RTC cannot update time during the power down state
Solution Approach 1:
The patent applies beforehand cushioning by implementing a freeze mechanism that protects the RTC counter during power down transitions. The counter is frozen in advance before the power state changes, creating a protective buffer that prevents data corruption during the vulnerable transition period, then resumes normal operation after power is restored
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable power supply to RTC and oscillation circuits across different battery types and prevents data loss during power down by regulating voltage and ensuring synchronized data transfer termination.
Implementation Method 1
A voltage supply circuit is provided that responds to a control signal to generate a supply voltage to power the RTC module and the oscillation circuit
Data Source
AI summary
A system on a chip includes a real time clock (RTC) module, a crystal oscillation circuit and a voltage supply circuit. The RTC module is coupled to provide timing functions and the crystal oscillation circuit is coupled to produce an oscillation. The voltage supply circuit is coupled to produce a supply voltage for at least a portion of the RTC module and the crystal oscillation circuit. The voltage supply circuit includes: a reference circuit coupled to produce a reference voltage based on the supply voltage; a transistor coupled to the battery IC pin, wherein the transistor produces the supply voltage based on a regulation signal and the battery voltage; an amplifier coupled to produce the regulation signal based on the reference voltage and a feedback representation of the supply voltage; and a start-up circuit coupled to enable the voltage supply circuit at battery connection.