Hello, forehead and hello.
The first part of the iPhone 11 repair cycle - more to come.
The full (graphic) version of this text is available at studionapraw.pl
or in the video version on YouTube
iPhone 11 temperature control is an extremely simple mechanism. Designed years ago for mac motherboards, it has been used in a whole range of products. The temperature control mechanism, contrary to appearances, has little to do with what comes to mind at first - but more about it in a moment.
A thermistor is a passive device that resembles an ordinary resistor. It is characterized by temperature dependence, which is directly related to its structure (with the construction material, which are, depending on the needs, alloys of nickel, vanadium, cobalt oxides, etc.). I am familiar with at least three types of thermistors, constructed depending on the environmental requirements: NTC, PTC and CTR. The iPhone 11 uses the NTC (Negative Temperature Coefficient) type, which in translation means Negative Temperature Coefficient.
Negative in this expression means "less than zero", i.e. an increase in temperature causes a decrease in the resistance of the element, thus increasing the flow (increasing the value of the current flowing through the element). The reaction to such a state will be appropriate actions of the supervising center, in this case a driver or a processor (with an appropriate software layer).
The entire support for such a solution cannot be omitted. Alone, one thermistor does not make "spring". A holding current is required, therefore it is always operated by a holding capacitor. Their mutual relationship is shown in the picture on the right. The thermistor measurement consists in checking the value of the peripheral resistance in laboratory conditions - normal (as a reminder - normal conditions: 1013.25 hPa at 0oC). Of course, in our case, the measurement at room temperature will have no effect on the result, but it should be remembered that in microelectronics you do not measure perceptibly warm elements. These should be cooled down beforehand or corrected for the environmental temperature.
Here, until one begs to mention the equations of resistance NTC, bandgap widths in a semiconductor, Planck and Boltzmann constants and dependencies in the functions of the Degree of Freedom and the absolute temperature. However ... after all, nobody reads it, so I will limit myself to the statement (:> harmonic constant = ~ 0.700) that the tested circuit should have a value of 0.700 on the active side in the diode measurement (calculated voltage drop of a polarized element in the forward direction).
In practice
iPhone 11, like any iPhone, measures its temperature in two ways. The first method, controlling the outside temperature, by means of two (source needed) sensors placed in the DOCK strip charging strip and the STOBE strip, on the torch / flash / microphone set # 2 tape (one of them is probably of the CTR type). Irregularities, especially the lack of reading from the device, will result in a cyclic reset, in the 170 second interval, and recording the fact in the external log. The second, internal - using NTC sensors, measures the temperature of the motherboard environment. The arrangement of the sets can be found in the attached graphic diagrams. The effect of the sensors' operation will be a stable temperature reading. The problems will (for now) appear as the message "you should cool down the iPhone before using it"
The first part of the iPhone 11 repair cycle - more to come.
The full (graphic) version of this text is available at studionapraw.pl
or in the video version on YouTube
iPhone 11 temperature control is an extremely simple mechanism. Designed years ago for mac motherboards, it has been used in a whole range of products. The temperature control mechanism, contrary to appearances, has little to do with what comes to mind at first - but more about it in a moment.
A thermistor is a passive device that resembles an ordinary resistor. It is characterized by temperature dependence, which is directly related to its structure (with the construction material, which are, depending on the needs, alloys of nickel, vanadium, cobalt oxides, etc.). I am familiar with at least three types of thermistors, constructed depending on the environmental requirements: NTC, PTC and CTR. The iPhone 11 uses the NTC (Negative Temperature Coefficient) type, which in translation means Negative Temperature Coefficient.
Negative in this expression means "less than zero", i.e. an increase in temperature causes a decrease in the resistance of the element, thus increasing the flow (increasing the value of the current flowing through the element). The reaction to such a state will be appropriate actions of the supervising center, in this case a driver or a processor (with an appropriate software layer).
The entire support for such a solution cannot be omitted. Alone, one thermistor does not make "spring". A holding current is required, therefore it is always operated by a holding capacitor. Their mutual relationship is shown in the picture on the right. The thermistor measurement consists in checking the value of the peripheral resistance in laboratory conditions - normal (as a reminder - normal conditions: 1013.25 hPa at 0oC). Of course, in our case, the measurement at room temperature will have no effect on the result, but it should be remembered that in microelectronics you do not measure perceptibly warm elements. These should be cooled down beforehand or corrected for the environmental temperature.
Here, until one begs to mention the equations of resistance NTC, bandgap widths in a semiconductor, Planck and Boltzmann constants and dependencies in the functions of the Degree of Freedom and the absolute temperature. However ... after all, nobody reads it, so I will limit myself to the statement (:> harmonic constant = ~ 0.700) that the tested circuit should have a value of 0.700 on the active side in the diode measurement (calculated voltage drop of a polarized element in the forward direction).
In practice
iPhone 11, like any iPhone, measures its temperature in two ways. The first method, controlling the outside temperature, by means of two (source needed) sensors placed in the DOCK strip charging strip and the STOBE strip, on the torch / flash / microphone set # 2 tape (one of them is probably of the CTR type). Irregularities, especially the lack of reading from the device, will result in a cyclic reset, in the 170 second interval, and recording the fact in the external log. The second, internal - using NTC sensors, measures the temperature of the motherboard environment. The arrangement of the sets can be found in the attached graphic diagrams. The effect of the sensors' operation will be a stable temperature reading. The problems will (for now) appear as the message "you should cool down the iPhone before using it"
