ADC Multiplexer Precharge Switching for Disconnection Detection
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Solution Overview
Problem
Existing semiconductor integrated circuit devices with analog/digital conversion circuit blocks face challenges in reliable disconnection detection due to voltage drops caused by current flow through high resistance external resistors, leading to errors in disconnection detection and increased detection time, especially in multi-channel configurations and high-speed applications.
Innovation Solution
The implementation of a semiconductor integrated circuit device with a multiplexer circuit that uses T-type switch circuits with a disconnection detection assist mode, where the intermediate nodes are set to the power supply voltage to prevent voltage drops and enable reliable disconnection detection without lengthening the sampling period, and the use of pull-up/pull-down circuits to manage charging and reset operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If disconnection detection is performed using existing ADC circuit blocks, then disconnection detection function is achieved, but voltage drops cause conversion errors and reduce detection reliability
Solution Approach 1:
The patent applies preliminary action by pre-charging the sampling capacitor to the power supply voltage VCCA before disconnection detection. This is achieved by controlling the switch circuit to connect the sampling capacitor to VCCA through a pre-charge switch, ensuring the capacitor starts at a known voltage level. This preliminary charging action eliminates voltage drops during detection and prevents conversion errors, thereby improving both reliability and measurement precision.
2Measurement precision
If sampling period is extended to allow capacitor charging, then detection accuracy improves, but detection time increases
Solution Approach 1:
The patent performs the charging action in advance by dedicating a pre-charge phase before the actual detection sampling. The sampling capacitor is charged to VCCA during this preliminary phase, so that during the subsequent detection phase, no additional charging time is needed. This separation of charging and detection into distinct time phases allows accurate detection without extending the overall detection time.
3Adaptability or versatility
If high resistance external resistors are used in multi-channel configurations, then circuit design flexibility improves, but voltage drops increase and cause conversion errors
Solution Approach 1:
The patent eliminates the problem of voltage drops from high resistance external resistors by pre-charging the sampling capacitor to VCCA before detection. Since the capacitor is already charged to the reference voltage, any voltage drops during the detection phase do not affect the accuracy of the measurement. This approach maintains circuit design flexibility while ensuring conversion accuracy.
4Reliability
If T-type switch circuits are used for channel selection, then channel isolation improves, but switch on-resistance causes voltage drops during detection
Solution Approach 1:
The patent pre-charges the sampling capacitor to VCCA before activating the T-type switch for channel selection. By establishing the capacitor voltage in advance, the subsequent switch on-resistance and any resulting voltage drops during channel switching do not affect the detection accuracy. The capacitor maintains its pre-charged voltage level throughout the detection process.
Data Source
AI summary
The semiconductor integrated circuit device includes a T-type switch circuit TS[k] that is between an input port A[k] and an input terminal Ain of an analog/digital conversion circuit and that includes first, second, and third PMOS transistors MP1, MP2, and MPc, and first, second, and third NMOS transistors MN1, MN2, and MNc; and a fourth PMOS transistor MPu for pre-charging the input terminal Ain to a power supply voltage VCCA. In detecting the presence or absence of a disconnection from the input port A[k] to a signal input terminal Vint[k], first, the input terminal Ain is pre-charged to the power supply voltage VCCA via the fourth PMOS transistor MPu and also the second NMOS transistor MN2 and the second PMOS transistor MP2 are turned on, and the first NMOS transistor MN1, the first PMOS transistor MP1, the third PMOS transistor MPc, and third the NMOS transistor MNc are turned off.