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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING K1464CA1 - two voltage comparators with an open collector output. Reference data
Encyclopedia of radio electronics and electrical engineering / Reference materials In the case of this microcircuit there are two independent (connected only by power circuits) comparators. Each of them is capable of operating in a wide range of input voltage values, is powered by both unipolar and bipolar sources, and has an open-collector output. Pn-p transistors work in the input stages of the comparators, so the input current is flowing. The input current is practically independent of the state of the output and the load resistance. The advantages of comparators should also include a relatively low current consumption and the ability to compare input signals that are close to zero in voltage. The microcircuit can be used in pulse generators, analog-to-digital converters, high-voltage logic elements, pulse detectors, and other nodes. In terms of output voltage levels, comparators are compatible with TTL, DTL, ESL and CMOS elements. The devices are packaged in a plastic eight-pin package of two types: 2101.8-1 (DIP-8) - K1464CA1R for traditional mounting and 430310.8-A (SO-8) - K1464CA1T, for surface mounting. The housing drawings are shown in fig. 1, a and b. In terms of electrical characteristics, both microcircuits are identical. The foreign analogue of the K1464CA1 chip is the LM393 (National Semiconductor Corporation).
The pinout of the microcircuit is shown in fig. 2
Basic electrical characteristics Input bias voltage, mV, max, at 5 V supply voltage and temperature*
Input current, nA, no more, at a supply voltage of 5 V and temperature
Difference of input current values, nA, no more, at supply voltage 5 V and temperature
Input common-mode voltage limits, V, at 30 V supply voltage and temperature
Current consumption, mA, no more, with an unconnected output, temperature +25 °C and supply voltage
* Everywhere ambient temperature. Limit values
* Since the input transistors are pnp, their collectors are connected to ground when powered unipolarly. When a negative voltage is applied to the input (in the nominal mode, it should not be less than zero), a direct current flows through the collector junction of the input transistors - flowing in, unlike flowing out, in normal mode. The specified value is the limit at which the input current must be limited in cases where the described comparator mode is possible. A typical circuit of an inverting comparator with voltage "hysteresis" is shown in fig. 3. The values of the lower and upper input threshold voltage Uthr.n and Uthr.v are determined by the following relationships:
Provided R1=R2=R3
Voltage values at the output of the comparator: U°=Us; U1 \u4d Upit - Iut RXNUMX. The saturation voltage Unas depends on the load current:
(Iut is the output leakage current; the current through the resistor R3 at high values of the resistance of the resistors R1-R3 can be ignored due to its smallness).
On fig. 4 shows a typical circuit of a non-inverting comparator with voltage hysteresis. For him
The transfer characteristics of the inverting and non-inverting voltage comparators described above are shown in fig. 5a and b, respectively. It should be noted that in order to ensure stable threshold voltage values, it is necessary to power the comparator, both inverting and non-inverting, and especially the exemplary voltage driver (in Fig. 3 and 4 - resistive dividers R1R2) from a stabilized source. Let's briefly consider several options for using the comparator. On fig. 6 shows a diagram of a rectangular pulse generator. It is based on an inverting voltage comparator with "hysteresis" and has the same switching thresholds. Elements R4, VD2 form the charging circuit of the capacitor C1 and determine the duration of the output pulse τi=R4·C1·ln2. Through the elements R3, VD1, the capacitor C1 is discharged, forming a pause tn=R3·C1·ln2. The processes occurring in the generator circuits are illustrated in Fig. 7.
Due to the fact that the comparators have an open collector output, they can be connected in a wired OR circuit. To do this, it is enough to combine the outputs of the comparators (pin 1 and 7) and connect the output of the element to the positive power wire through a common load resistor with a resistance of 3 kOhm. On fig. 8 shows a schematic of a zero crossing detector. The basis of the node is an inverting voltage comparator with "hysteresis". With the resistor values indicated in the diagram, the threshold levels given to the input correspond to: Uthr.n = -0,0023Upit; Uthr.v \u0,0027d 1Upit. At the output, the detector generates a short pulse each time the input voltage passes through "zero". Diode VDXNUMX protects the comparator from input current overload during negative half-cycles of the input signal. Authors: M.Shapolvalova, A.Shestakov, N.Minina, Bryansk
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