Avalanche Diode Arrangement With Latch Comparator For Excess Bias Monitoring
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Solution Overview
Problem
Avalanche diodes, particularly single photon avalanche diodes (SPADs), face challenges in efficiently monitoring and controlling excess bias voltage, leading to high power consumption and variability in performance due to temperature changes, which affects detection accuracy and reliability in applications like time-correlated single photon counting and time-of-flight measurements.
Innovation Solution
The implementation of an avalanche diode arrangement that includes a latch comparator and a quenching circuit, allowing for the direct monitoring of excess bias voltage and reducing power consumption by enabling the latch comparator only during photon detection events, with a digital control circuit managing the comparator's enable signal to minimize idle state power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the latch comparator is continuously enabled to monitor excess bias voltage, then monitoring accuracy is improved, but power consumption increases
Solution Approach 1:
The latch comparator is enabled periodically only during the integration period when monitoring is required, rather than continuously. The enable signal activates the comparator during specific time windows (when the integration switch is closed) and keeps it disabled otherwise, achieving periodic operation that reduces power consumption while maintaining monitoring accuracy during critical periods.
2Stability of the object's composition
If the integration capacitor has large capacitance to reduce ripple voltage, then voltage stability is improved, but the time to reach threshold voltage increases
Solution Approach 1:
The integration capacitor is pre-charged to the reference voltage Vref through the integration switch before the monitoring period begins. This preliminary action ensures that the capacitor starts at the correct voltage level, allowing the excess bias voltage to be integrated without delay and reaching the threshold voltage faster, thus reducing the time loss while maintaining voltage stability.
3Reliability
If the avalanche diode operates with high excess bias voltage to improve photon detection sensitivity, then detection sensitivity is improved, but dark count rate increases
Solution Approach 1:
The circuit continuously monitors the excess bias voltage through the latch comparator and provides feedback control. When the integrated voltage reaches the threshold (indicating excessive excess bias voltage), the system detects this condition and can adjust the bias voltage accordingly. This feedback mechanism allows the system to operate at high excess bias voltage for improved sensitivity while automatically detecting and correcting conditions that lead to high dark count rates.
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
This solution enables low power consumption and accurate monitoring of excess bias voltage, maintaining consistent SPAD performance across temperature variations, thereby enhancing detection accuracy and reliability in photon detection applications.
Implementation Method 1
When the photon hits the SPAD, an electron-hole pair is generated and a very high short current pulse is generated due to the very high electrical field
Implementation Method 2
The SPAD is reverse biased with a bias voltage higher than a breakdown voltage of the avalanche diode. When the photon hits the SPAD, an electron-hole pair is generated
Data Source
AI summary
A avalanche diode arrangement comprises an avalanche diode (11) that is coupled to a first voltage terminal (14) and to a first node (15), a latch comparator (12) with a first input (16) coupled to the first node (15), a second input (17) for receiving a reference voltage (VREF) and an enable input (21) for receiving a comparator enable signal (CLK), and a quenching circuit (13) coupled to the first node (15).