Okay, let's break down the provided text. Here's a comprehensive summary, categorized for clarity, including the key information extracted from the multiple figures (which I'm interpreting based on the descriptions).

1. Product Overview: AD22105

️· What it is: A single-supply semiconductor thermostat switch. Essentially, it combines a temperature sensor, comparator, and output switch in one chip.
️· Functionality: Switches on/off based on temperature. User can program the switch temperature using an external resistor.
️· Hysteresis: The temperature at which it turns *off* (relaxes) is slightly lower than the temperature at which it turns *on* (switches). This difference is called hysteresis, typically around 4°C.
️· Operating Range: -40°C to +150°C.

2. The Setpoint Resistor (R_SET)

️· Purpose: Determines the switch temperature.
️· Equation: R_SET = (39 Ω°C) / (T_SET ( °C ) + 281.6 °C) – [90.3] [k]Ω
- `T<sub>SET</sub>` is the desired setpoint temperature in degrees Celsius.
️· Connection: Should be connected directly between the R_SET pin (Pin 6) and the GND pin (Pin 3).
️· Resistor Type: Can be almost any resistor type. Metal-film resistors (1% tolerance) are recommended for best accuracy.
️· Compound Resistors: If a standard resistor value isn't readily available, a combination of two resistors (in series or parallel) can be used. Consider using a more precise resistor for the majority of the needed resistance and a less precise one for fine tuning.

3. Effect of Resistor Tolerance and Thermal Drift on Setpoint Accuracy

️· Figure 3 Interpretation: Shows typical accuracy error in setpoint temperature as a function of the programmed setpoint temperature, assuming an ideal resistor.
️· Figure 4 Interpretation: Shows _additional_ setpoint error as a function of resistor tolerance. This error is *added* to the initial accuracy error specified in the part's datasheet. (Important to note: this is an *additional* error).
️· Example: A 1% metal film resistor chosen for an R_SET of 1000Ω, could have 0.2% tolerance, this leads to error of approximately –0.2 ° C, and the resistor's tolerance could lead to additional error of 0.2 °C.

4. Other figures

️· Figure 3: Accuracy error vs programmed setpoint.
️· Figure 12: Thermal response time.

Key Takeaways & Purpose of the Text

️· Design Guidance: The document is primarily aimed at engineers designing systems that use the AD22105.
️· Accuracy is Critical: The text emphasizes the importance of resistor selection and tolerance to achieve the desired switching temperature accuracy.
️· Troubleshooting: It provides guidance on how to deal with situations where standard resistor values aren't available.
️· Thorough Understanding Required: A careful read and understanding of the equations and figures is essential for proper implementation and accurate performance.



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