The electronic component tl 431 is one of the integrated circuits, whose production has been put on a mass flow since 1978. It is widely used in most computer power supplies, televisions and other home appliances as a precision programmable voltage reference. In practice, there are several tl431 switching schemes.
Content
- Electronic element device
- Principle of operation
- Pinout tl341
- Specifications
- Connection diagrams
-
Independent Chip-Based Devices
- Current stabilizer
- Sound indicator
- Functional test with a multimeter
Electronic element device
The microcircuit has a simple design, consisting of the following elements: a housing, an operational amplifier (OA), an output tl431 transistor, and a reference voltage source. A feature of this microcircuit is that it performs the functions of a zener diode.
A highly stable 2.5 volt reference voltage source connected to the inverse input of the op amp (-), the emitter of the transistor and ground with the help of two common points, a silicon one is also included in the reference pressure circuit diode. It is designed to prevent reverse current build-up and protects against polarity reversal. Direct input ® is intended for receiving signals from other boards, as well as for powering the amplifier. It is connected through a diode to the collector of the transistor also through a common point. The op-amp output is connected to the base of the transistor.
It should be remembered that the transistor used in microcircuits of this series is capable of withstanding loads up to 0.1 A and 36 V.
Principle of operation
The operation of the microcircuit is based on the principle of excess voltage applied to the direct input of the op-amp over the reference one. When U (direct input voltage) is less than or equal to Vref (output reference voltage), it will be such a low voltage, due to which the transistor will not open, and the current through the anode-cathode circuit will not to do. As soon as U exceeds Vref at the op-amp output, a voltage is generated that can open the transistor and force current to flow from the cathode to the anode, which makes the microcircuit work.
Pinout tl341
TL 341 is a 3-pin IC. Each leg has its own name 1 - reference (output), 2 - anode (anode) and 3 - catode (cathode).
In practice, the pinout is different and depends on the type of housing chosen by the manufacturer during the manufacture of the product. The TL431 is available in a wide variety of packages, from the ancient TO-92 to the modern SOT-23. The pinout of the tl431, depending on the type of case, is shown in Figure 3.
The analogs of domestically produced tl431 are KR142EN19A and K1156EP5T microcircuits. Foreign counterparts include:
- KA431AZ;
- KIA431;
- HA17431VP;
- IR9431N;
- AME431BxxxxBZ;
- AS431A1D;
- LM431BCM.
Specifications
The main technical characteristics of the tl 341 microcircuit are:
-
anode-cathode voltage, which can vary from 2.5 to 36 V; - anode-cathodic current ranging from 1 mA to 0.01 A;
- source accuracy, depending on the presence of a letter after the numbers, if the letter is absent, then this parameter is 2%, present, A (1%) or B (0.5%).
From the characteristics it can be seen that the microcircuit can be used with a fairly wide voltage range, but the current carrying capacity is very small. To get more serious, powerful transistors are connected to the cathode circuit, which regulate the output parameters.
Connection diagrams
The tl 431 microcircuit is an integral zener diode. It has three switching schemes:
- at 2.48 V (1);
- 3, 3 V (2);
- by 14 V.
Option 1: 2.48V circuit.
The 2.48 volt zener diode switching circuit is equipped with a single-stage converter. The average operating current in such a system is 5.3 A. A circuit consisting of two parallel-connected resistors (2.4 and 2.26 kΩ each) is mounted to the ref pin (reference voltage circuit). These resistors are preliminarily supplied with a voltage of 5 V, which, after passing through the circuit, turns into 2.48.
In order to increase the sensitivity of the zener diode, various modulators are used, mainly of the dipole type with a capacitance of less than 3 pF (picofarad). Zener diodes are connected to the cathode.
Option 2: 3.3V switching circuit.
The 3.3V circuit also uses a single-stage converter and a 1K resistor connected to the cathode. A third-party 3 V power supply is placed in front of the resistance. A 10 nF capacitor connected to ground is connected to the (ref) pin. The anode in a similar scheme is planted directly to the ground, and the cathode and input circuits are connected by two common points.
The problem with this switching circuit is the high probability of a short circuit (short circuit). In order to reduce the risk of a short circuit, a fuse is mounted after the zener diodes.
To amplify the signal, special filters are connected to the output. In such a switching circuit, the average voltage and current are 5 V / 3.5 A, and the stabilization accuracy is less than 3%. The zener diode is connected through a vector adapter, so you need to select a resonant type transistor. The average modulator capacitance should be 4.2 pF. Triggers can be used to increase the conductance of the current.
Independent Chip-Based Devices
This microcircuit is used in power supplies for TVs and computers. However, on its basis, it is possible to draw up independent electrical circuits, some of which are:
- current stabilizer;
- sound indicator.
Current stabilizer
A current stabilizer is one of the simplest circuits that can be implemented on a tl 341 microcircuit. It consists of the following elements:
- power supply;
- resistance R 1, connected with a common point to the + power line;
- shunt resistance R 2 to - power line;
- a transistor, whose emitter is connected to the - line through the resistor R 2, the collector to the output - the line, and the base through a common point to the cathode of the microcircuit;
- tl 341 microcircuits, whose anode is connected to the - line using a common current, and the ref pin is connected to the emitter circuit of the transistor also using a common point.
The main role in this circuit is played by the shunt resistor R 2, which, due to feedback, sets the value, the voltage is equal to 2.5 V. Because of this, the output current will take the following form: I = 2.5 / R2.
Sound indicator
The sound indicator based on tl 341 is a simple circuit shown in Figure 5
Such a sound indicator can be used to monitor the water level in any container. The sensor is an electronic circuit in a housing with two lead-out electrodes made of stainless steel, one of which is located 20 mm higher than the other.
At the moment of contact of the sensor terminals with water, the resistance decreases and tl 341 transitions to linear mode through the resistors R 1 and R 2. This contributes to the appearance of autogenation at the resonant frequency and the formation of a sound signal.
Functional test with a multimeter
The question of how to check the tl431 with a multimeter is asked by many. The answer to it is simple enough to check the tl341 microcircuit or its modification tl431a you need to do the following:
- Build a simple test circuit using a microcircuit and a key.
- Close the switch circuit and take measurements. The multimeter should show a reference voltage of 2.5 V.
- Open circuit and measure. The meter display should read 5V.
