# How does this switch work

Discussion in 'Digital Circuit Design' started by ForumlaM, Dec 2, 2017.

1. ### ForumlaM Thread Starter New Member

Dec 2, 2017
1
0
Hi

I would like to use a switch for example the switch HMC221B (datasheet is attached) . As we can see on the attached picture.

For that switch, as we can see in the datasheet, we need to add a circuit with two 74HC04. I would like to know from that circuit what is the meaning of VCTL and how do I create it ? Do we control both A and B both in same time with one input named VCTL? Do we have the control over VCTL?

And if I put between 3V and 5V for VCTL does it mean that VCTL=high?
If I put 0 V at VCTL, does it mean VCTL=low and cause B to be high and A to be low?
Do I really need to use two 74HC04 in that case?

Thank you

• ###### hmc221b.pdf
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Last edited: Dec 2, 2017

Jan 15, 2015
4,057
1,848
TYPICAL APPLICATION CIRCUIT Two cascaded, CMOS inverters, biased with VDD = 5 V, can generate complementary control voltages, VCTL = 0 V/5 V, for the A and B inputs. Therefore, the HMC221B can be controlled from a single CMOS input line (see Figure 15).

Your posted circuit is Figure 15, VCTL (the control voltage) can be 0 volts for an Off state and 5 volts for an On state. Using a hex inverter like the 7404 series allows the switch to toggle. When A is High, B is Low and when B is High A is Low. Control Voltage Range (A and B) is −0.2 V dc to 12 V dc. See the control inputs on the data sheet.

Ron

3. ### WBahn Moderator

Mar 31, 2012
23,587
7,216
Are you SURE you want to use that switch? Are you really switching low-power RF signals?