Clock Gating Circuit for Fast Chip-Select Timing in DDR Memory
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Solution Overview
Problem
High-speed operation of DDR synchronous memory devices faces challenges in reducing current consumption, particularly at low power-supply voltages, due to short setup and hold times of chip select signals, leading to difficulties in controlling internal clocks effectively.
Innovation Solution
A clock control device that includes a chip-select-signal control block to generate a fast chip select signal and a clock control block to drive a clock signal based on the chip select signal, using a latch unit and delay unit to synchronize and control the clock enable signal, thereby optimizing internal clock operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the operation frequency of the memory device is increased to achieve high-speed operation, then the bandwidth and processing speed are improved, but the setup time and hold time of the chip select signal become extremely short, causing defective margins between address and operation command
Solution Approach 1:
The chip select signal control block is divided into multiple functional units: a latch unit that captures the chip select signal at specific timing, a delay unit that provides controlled time delays, and a fast chip select signal generation unit. This segmentation allows each unit to handle specific timing requirements independently, ensuring reliable signal generation even at high operation frequencies where the overall chip select signal duration is extremely short.
2Use of energy by moving object
If the internal clock is controlled to operate only during specific intervals to reduce current consumption, then power efficiency is improved, but at low power-supply voltages and high speeds, the short chip select signal duration makes it difficult to determine appropriate control intervals
Solution Approach 1:
The latch unit performs preliminary action by capturing the chip select signal at a predetermined timing (rising or falling edge) before the actual clock operation begins. This early latching establishes a reliable reference point that determines when the internal clock should be activated, ensuring proper timing even when the overall chip select signal duration is extremely short at high speeds and low voltages.
Solution Approach 2:
The delay unit acts as an intermediary between the latched chip select signal and the fast chip select signal generation. It introduces controlled time delays that ensure the clock control block receives properly timed signals, bridging the timing gap created by the extremely short chip select signal duration at high operation frequencies while maintaining clear intervals for clock operation control.
3Device complexity
If a conventional chip select signal setup time is used to control the internal clock, then the control logic is simple, but at high operation frequencies the setup time becomes insufficient to reliably control the clock during the required interval
Solution Approach 1:
The system dynamically adapts to high operation frequencies by using a latch unit that captures the chip select signal at specific edges and a delay unit that provides adjustable time delays. This dynamic approach replaces static setup time assumptions with adaptive timing control, ensuring reliable clock control even when the chip select signal duration becomes extremely short at high frequencies, without requiring overly complex control logic.
Data Source
AI summary
A clock control device is disclosed, which relates to a technology for reducing the amount of current consumption when a semiconductor device operates at a high speed. The clock control device includes: a chip-select-signal control block configured to generate a chip-select-control signal by latching a chip select signal, and output a fast chip select signal according to the chip-select-control signal; and a clock control block configured to drive a clock signal in response to the fast chip select signal when a command clock enable signal is activated, thereby generating a clock control signal, wherein the chip-select-signal control block latches the chip-select-control signal, and controls the chip-select-control signal to be toggled after the command clock enable signal is transitioned.