In the field of intelligent security, energy-saving lighting and automatic control, CXRT2131, as a digital-analog hybrid chip designed for microwave and infrared signal processing, has become an ideal choice for battery-powered systems with its ultra-low power consumption, high integration and flexible trigger mechanism. This article will analyze its core features, typical application circuits and design techniques to help engineers develop induction products efficiently.
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[ CXRT2131 ]"
Introduction
In the field of intelligent security, energy-saving lighting and automatic control,CXRT2131As a digital-analog hybrid chip designed for microwave and infrared signal processing, it is an ideal choice for battery-powered systems with its ultra-low power consumption, high integration and flexible trigger mechanism. This article will analyze its core features, typical application circuits and design techniques to help engineers develop induction products efficiently.
1. Core Features: Why CXRT2131?
1.1) Very low static power: Power consumption <45μA when powered by 3V, <75μA when powered by 5V, significantly extending battery life.
1.2) High compatibility and anti-interference ability: High input impedance operational amplifier is suitable for various sensors, and the two-way amplitude discriminator effectively suppresses environmental noise.
1.3) Flexible timing control:Built-in delay timer (Tx) and blocking timer (Ti), through the external RC to adjust the oscillation frequency (formula:Tosc=0.4R·C), to achieve 5μs ~ 50s accurate timing.
1.4) Wide voltage operation: 3V ~ 5.5V power supply range, compatible with lithium battery/button battery power supply scheme.
2. Key Pin Function Analysis
| Pin | Name | Function Description |
|---|---|---|
| 3 (VC) | Trigger Prohibited End | Lock output when voltage <0.2Vdd; trigger is allowed when voltage> 0.2Vdd (combined with photoresistor to realize day and night mode switching) |
| 4 (A) | Trigger mode end | A = "1": Repeatable trigger (signal continuously refreshes Tx);A = "0": Single trigger (reset after Tx Ti) |
| 6 (OUT) | Signal output | Strong driving ability: ± 25mA at 5V (can directly drive LED/relay) |
| 7 (CT) | oscillation control | External capacitor Cr pull-up resistor RT setting frequency (example: R = 100K, C = 1nF & rarr; f = 20kHz) |
3. Typical Application Scenarios and Circuit Design
3.1. Human body induction lighting system(Figure 6-1a)
3.1.1) Core ComponentsPIR infrared sensor drives LED CXRT2131 S8050 triode.
3.1.2) Anti-interference design：
3.1.2.1)The first stage op amp gain A1 = R3/R2 (typical value 300 times), the second stage is fixed 30 times, and the total gain is 9000 times.
3.1.2.2)C3(10nF) filter out high-frequency noise, C2(10μF) blocking capacitor to stabilize the signal.
2. Relay Control Security Equipment(Figure 6-1b) Drive the S8050 control relay through the OUT pin, and the HT7533 LDO isolates power supply noise to avoid false triggering of Vdd fluctuations.
3. Photosensitive microwave dual-mode induction scheme(Figure 6-1c):Photoresistor (RG) connected to VC terminal: Turn off the trigger when the light intensity> threshold to realize "sleep during the day and start at night".
4. Design Advanced Skills
4.1. Timer Model Selection Guide
| Model | Tx (number of clocks) | Ti (number of clocks) | Proportion K | Applicable Scenarios |
|---|---|---|---|---|
| CXRT2131A | 100,000 | 20,000 | 5 | Short delay (<15s) |
| CXRT2131G | 100,000 | 2,000 | 50 | Long delay short blocking (anti-interference) |
Calculation example: When Tosc = 50μs (R = 100K, C = 1nF), the total timing time of the CXRT2131D:
Tx = 100,000 × 50μs = 5s
Ti = 5,000 × 50μs = 0.25s
T_total = 5.25s
4.2. Trigger mode selection principles.
4.2.1) Non-repeatable trigger (A = "0"): Suitable for alarms to avoid continuous false alarms.
4.2.2) Repeatable trigger (A = "1"): Suitable for lighting system, the human body keeps constantly moving.
4.3. Power supply design key
4.3.1)Add 10μF 0.1μF capacitor combination filter, using HT7533 and other LDO isolation motor/relay impulse current.
5. Limit Parameters and Electrical Characteristics
5.1) Absolute Maximum(beyond which will be permanently damaged):
5.1.1) Supply voltage Vdd:-0.3V ~ 6V
5.1.2) Working temperature:-45 ℃ ~ 85 ℃
5.2 typical performance(Vdd=5V, TA=25℃):
5.2.1) Quiescent current ICC:65 μA (typical)
5.2.2)OUT drive capability: output high level ≥ 4.5V at 10mA load
Conclusion
CXRT2131 greatly simplifies the development process of microwave infrared induction products through a highly integrated design (op amp comparator dual timer). Its mA-level power consumption and flexible trigger logic are especially suitable for battery-powered smart homes and IoT terminal devices. Developers can choose the appropriate model suffix (A ~ G) according to actual needs, and optimize the RC parameters to balance sensitivity and anti-interference.
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