Common analog switch chip pin, function and application circuit

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Common analog switch chip pin, function and application circuit

CMOS analog switch is a controllable switch, it is not like a relay can be used in large current, high voltage situation, only suitable for processing amplitude not exceeding its operating voltage, the current small analog or digital signal.

first, commonly used CMOS analog switch function and pin introduction
1. Four bidirectional analog switch CD4066
The PIN function of the CD4066 is shown in 1. Each package has 4 independent analog switches, each analog switch has input, output, control three terminals, wherein the input and output are interchangeable. When the control terminal is raised, the switch is on, and when the control end is lowered, the switch ends. When the analog switch is on, the on-resistance is dozens of ohms, and when the analog switch is cut off, it exhibits a high impedance, which can be seen as an open circuit. Analog switches transmit both digital and analog signals, and the upper frequency of the analog signals that can be transmitted is 40MHz. The crosstalk between the switches is very small and is typically -50db.

2. Single eight analog switch CD4051
The CD4051 pin function is shown in Figure 2. The CD4051 corresponds to a single-pole eight-throw switch, which channel is switched on and is determined by the input 3-bit address code ABC. The truth tables are shown in table 1. "INH" is the forbidden end, when "INH" = 1 o'clock, each channel is not connected. In addition, the CD4051 has another power-supply vee to use as a level shift, which allows the digital signal provided by a CMOS circuit that normally operates under a single set of power supply conditions to directly control this multi-switch and enable the multi-switch to transmit peak-to-peak AC signals up to 15V. For example, if the analog switch power supply vdd=+5v,vss=0v, when the vee=-5v, as long as the analog switch to apply the 0~5V digital control signal, can be controlled amplitude range of -5v~+5v analog signal.

Table 1

Input status				Connect Channel
INH	C	B	A
0	0	0	0	"0"
0	0	0	1	"1"
0	0	1	0	"2"
0	0	1	1	"3"
0	1	0	0	"4"
0	1	0	1	"5"
0	1	1	0	"6"
0	1	1	1	"7"
1				are not connected

3. Dual four-way analog switch CD4052
The PIN function of the CD4052 is shown in Figure 3. The CD4052 is equivalent to a double-knife four-throw switch, which channel is connected, the input address code AB to determine. The truth tables are shown in table 2.

Table 2

Input status			on channel
INH	B	A
0	0	0	" 0 "X," 0 "Y
0	0	1	"1" X, "1" Y
0	1	0	"2" X, "2" Y
0	1	1	" 3 "X," 3 "Y
1			are not connected

4. Three set of two-way analog switch CD4053
The PIN function of the CD4053 is shown in Figure 4. CD4053 contains 3 sets of SPDT switches, 3 sets of switches specifically connected to which channel, the input address code ABC to determine. The truth tables are shown in table 3.

Table 3

Input status				Connect Channel
INH	C	B	A
0	0	0	0	CX, BX, AX
0	0	0	1	CX, BX, AY
0	0	1	0	CX, by, AX
0	0	1	1	CX, by, AY
0	1	0	0	CY, BX, AX
0	1	0	1	CY, BX, AY
0	1	1	0	CY, by, AX
0	1	1	1	CY, by, AY
1				are not connected

5.16-Way Analog switch CD4067
The PIN function of the CD4067 is shown in Figure 5. The CD4067 is equivalent to a single pole 16 throw switch, which channel is connected, which is determined by the input address code ABCD. The truth tables are shown in table 4.

Table 4

D	C	B	A	INH	Connect Channel
0	0	0	0	0	"0"
0	0	0	1	0	"1"
0	0	1	0	0	"2"
0	0	1	1	0	"3"
0	1	0	0	0	"4"
0	1	0	1	0	"5"
0	1	1	0	0	"6"
0	1	1	1	0	"7"
1	0	0	0	0	"8"
1	0	0	1	0	"9"
1	0	1	0	0	"10"
1	0	1	1	0	"11"
1	1	0	0	0	"12"
1	1	0	1	0	"13"
1	1	1	0	0	"14"
1	1	1	1	0	"15"
				1	are not plugged in

ii. Typical Application examples
1. Single-button volume controller
The single-button volume controller circuit is shown in Figure 6. The VMOs tube VT1 acts as a variable resistor and is connected to the audio device's volume potentiometer output to the ground. The resistance of the VT1 between the D-pole and the S-pole varies inversely with the VGS, so control of the VGS can be achieved by controlling the volume size. The VT1 G-pole is connected with 3 analog switch s1~s3 and a 100μf capacitor, where the 100μf capacitor plays a voltage hold. Because of the high resistance between the G-pole and the S-pole of the vmos tube, the voltage on the 100μf capacitor can remain unchanged for a long time. Analog switch S1 for the capacitor to provide a charging circuit, when the S1 conduction, the power supply through the S1 to the capacitor charge, the voltage on the capacitor is increasing, so that the VT1 on the resistance is getting smaller, so that the volume is also getting smaller. The analog switch S2 provides the discharge circuit for the capacitance, when the S2 conduction, the capacitance through the S2 discharge, the capacitance voltage drops continuously, makes the volume more and more big. Analog switch S3 start volume reset function, when the power supply in the S3 control end of a short positive pulse, so that S3 conduction, because the resistance with the S3 connection is small, so that the capacitor is quickly charged to a certain voltage, so that the starting volume is in a small state. F1~f6 and its peripheral components are composed of short and long pulse recognition circuits. At rest, the F1 and F2 inputs are high, and when the button switch an is pressed for a long time, the F4 output becomes high, By 100k resistor to the 3.3μf capacitor charge, when the charging voltage exceeds the CMOS gate conversion voltage, the F5 output from high to low, F6 output from low to high, analog switch S2 conduction, 100μf capacitance discharge, the volume becomes larger. At the same time, the F1 output is also high, but also to the capacitor charge, but the F1 output of a positive jump is not enough to make the capacitor voltage over the conversion voltage, so the F2 output is still high, F3 output low level, analog switch S1 to maintain the cutoff. When the continuous push button switch an, the F4 output is constantly changing, the output is high, the capacitor is charged, and the output becomes low, the capacitor and quickly through the diode VD3 discharge, so the capacitance on the voltage is always not up to the conversion voltage, so the F6 output has been low. And at this time F1 output continuous high and low change, through the diode rectifier constantly to charge the capacitor, so that the 3.3μf capacitor voltage quickly reached the conversion voltage, F2 output is low, F3 output is higher, analog switch S1 conduction, to the capacitor charge, the volume becomes smaller. Thus, a button switch is used to control the volume size.

2. Four-channel video signal switcher
The four-way video signal switcher circuit is shown in Figure 7. "With non" gate YF3, YF4 composed of pulse oscillator, oscillation frequency is adjusted by 100k potentiometer. If the adjustment range is not enough, the 0.47μf capacitor and 100k resistor can be replaced appropriately. The pulse oscillator is controlled by a bistable circuit composed of YF1 and YF2, and when pressed S1, the YF1 output low level, the pulse oscillator stops the vibration, and when S2, the YF1 outputs high, and the pulse oscillator starts to oscillate. The output of the pulse oscillator is used as the clock of the CD4017 decimal counter, so that the y0~y3 in turn appears high, the corresponding four analog switches in turn, the video signal from the VI1~VI4 input is switched to the output, the four-way video signal is completed. Obviously, adding a piece of CD4066 can be made into eight video signal switcher, corresponding to the Y0~Y7 for analog switch control, Y8 connected to the CR. And so on, can be made more multiplex video signal switcher. Moreover, the input and output can also be other forms of signal. If the video and audio signals are required to be transmitted, then the corresponding number of analog switches can be connected.

3. CNC Resistor network
Figure 8 shows the digital control resistor network resistor value size circuit. In Figure 8, the four independent switches of the CD4066 are connected to the four string resistors respectively, and the values of the resistors are selected according to the bits weight relationship. When a switch is switched on, and the resistor connected to the switch is shorted, the resistor is assumed to be Rron (Ron is the on-resistance of the analog switch), and when a switch is switched off, the resistance at both ends remains unchanged, assuming the resistance value Rroff (Roff is the resistor when the analog switch is disconnected). Four switch control driven by four-bit binary number A, B, C, D control, therefore, in a, B, C, d terminal input different four-bit binary number, can control resistor network resistance change, and from it obtained 2~16 different resistance values. According to the resistance value given in Figure 8, the resistor network corresponds to 16 kinds of resistance listed in table 5.

Table 5

Input binary number				Resistance value (MΩ)
D	C	B	A
0	0	0	0	3.75
0	0	0	1	3.50
0	0	1	0	3.25
0	0	1	1	3.00
0	1	0	0	2.75
0	1	0	1	2.50
0	1	1	0	2.25
0	1	1	1	2.00
0	0	0	0	1.75
1	0	0	1	1.50
1	0	1	0	1.25
1	0	1	1	1.00
1	1	0	0	0.75
1	1	0	1	0.50
1	1	1	0	0.25
1	1	1	1	4xron≈2kω

4. Volume Adjustment circuit
The volume adjustment circuit is shown in Figure 9. The audio signal is input by the VI terminal, and the voltage divider resistor R11 and the DC capacitor are added to the Add/subtract resistor network composed of R1~R10. CD40192 for the decimal plus/minus counter, "and non" gate YF3, YF4 constitute a low-frequency oscillator, "and non" gate YF1, YF2 are counting end of the CPU and the counter-counting end CPD Count Gate.

When the D1 terminal is high, the gate YF1 Open, the low-frequency pulse by YF1 added to the CD40192 CPU side, making it an addition count, output q0~q3 data increase, so that the 16-way analog switch knife to the low-end conversion, order to r1~r10, the resistance increased, after and R11 by the pressure, Increase the output audio signal vo; When the D2 end is high, the gate YF2 Open, the low-frequency pulse by YF2 added to the CD40192 CPD end, making it a subtraction count, the output Q0~Q3 data reduction, so that the 16-way analog switch to the high-end conversion of the knife, order to R10~R1, the resistance is reduced, The output audio signal Vo is reduced after being divided by the R11.

Common analog switch chip pin, function and application circuit