Analog multi-way switch expansion circuit

This article brings you two expansion circuits of the analog multi-way switch CD4051.

Expansion circuit of analog multi-way switch CD4051

When there are many sampling channels, two or more multi-way switches can be connected in parallel. The method of extending two 8-way switches into a 16-way multi-way switch is as shown in the figure.

CD4051 is a single-ended input 8-channel multiplexer. It has 3 channel selection input terminals A, B, and C and an inhibit input terminal INH. The input terminals A, B, and C signals are used to control the selection of one of the 8 channels. Connected. In practical applications, if there are more than 8 channels of measured parameters, using a CD4051 multi-channel switch cannot meet the requirements for the number of channels. For this, multiple CD4051s can be connected and expanded. The figure above shows the connection diagram of a 16-channel multi-switch composed of two CD4051s. When the multi-way switch of chip 1 is turned on, all the multi-way switches of chip 2 are turned off; conversely, when the multi-way switch of chip 2 is turned on, all the multi-way switches of chip 1 are turned off. Therefore, only one address (or data) line serves as the selection signal for the control terminals of chip 1 and chip 2, and the channel selection input terminals of the two chips share a set of address (or data) lines.

By changing the state of the channel selection lines D3~DO, one of the 16 channels INO~IN15 can be selected. D3 is used to control the level of the INH input terminals of chip 1 and chip 2. When D3-0, chip l is entered. Under this premise, the state of DZ-DO terminal changes, and only one of INO~IN7 can be selected. When D3-1, the inverter becomes low level, and chip 2 is selected. At this time, the status of the three lines D2--;DO can turn on the corresponding channels among IN8-IN15.

Expansion circuit 2 of analog multi-way switch CD4051

If more channels are needed, and the expansion of two multi-channel switches still cannot meet the system requirements, at this time, the control terminal INH of CD4051 can be controlled through the decoder, and four CD4051 chips can be combined to form a 32-channel or 16-channel differential input. system, as shown in the figure below.

The input method of the signal under test can usually be divided into two types: single-ended input or double-ended input. The advantage of double-ended input is that it has a high common-mode rejection ratio, that is, it can suppress large common-mode interference. In circle 27-7, multi-channel analog switches U1~U4 (CD4051) provide 32 channels (CHO~CH31). CPU output ~ byte control word storage AD register (74LS273), in which .DO, pi phase D2 bits are used as the address lines A, B and C of the multi-channel mode twist switch, and D-D6 bits are used as the control signals of U1-U4 respectively. Face, I.

If you choose single-ended input, you can short-circuit 1-Z, 3-4 of short-circuiting post KA, and then short-circuit 2-3, 5-6 of short-circuiting post KB, which can provide 32 input signal paths (CHO ~CH31).

If you choose double-ended input, that is, there are 16 input signals, each signal occupies two terminal switches, among which CHO~CH15 are the positive signal terminals Vl+, and CH16-CH31 are the negative signal terminals Vl-. For this purpose, short-circuit 2-3 of short-circuiting column KA, and then short-circuit 1-2, 415 of short-circuiting column KB. At this time, the D3 bit of the control word serves as the control signal surface for U1 and U3, and the D4 bit serves as the control signal LEN for U2 and U3. In this way, 16 double-ended input signal paths are provided.