Path: EDN Asia >> Design Ideas >> IC/Board/Systems Design >> IC offers versatile toggle functions
IC/Board/Systems Design Share print

IC offers versatile toggle functions

26 Feb 2016  | Louis Vlemincq

Share this page with your friends

The circuit in the figure features not only as many as six channels in a single IC package, but also a high level of additional flexibility. The configuration of Output 1 is a "plain-vanilla" toggle. A resistive divider comprising R1 and R2 provides a midsupply bias to all the channels through resistors R3, R6, R7, R10, and R12. Because the bias voltage of R1/R2 is within the hysteresis range of the gates, they behave as flip-flops, retaining their high or low state in a stable manner.

Figure: This circuit shows multiple Schmitt-trigger inverters functioning as a variety of set/reset toggles.

Debouncing capacitors C2, C3, C4, and C5 charge to the level of the output. Pushing switch S1 inverts the output state because of the inverting action of the gate. This state remains stable because, in the first gate's circuit, for example, R4's value is larger than that of R3, and R4 cannot overcome the hysteresis threshold of the gate. Only the discharge of C2 can accomplish that task. When you release the pushbutton, C2 fully charges after the debouncing delay, and the circuit is ready for another inversion. C1 provides a general power-on-reset feature to all the channels. If your circuit requires only one channel, you can directly connect R1 and R2 to the input of the gate, omitting R3.

Output 2 has the same toggle function as Output 1 but also includes a direct reset. Output 3 works only in a set/reset mode; the position of R8 determines the priority state. Output 4 also has a toggle action, but you can set or reset it to a state opposite that of Output 3. Output 5 works in a similar manner, except it allows only a conditional reset because of the position of D1. Output 5 also includes a forced, nonpriority set. You can mix and match all these functions, providing almost unlimited versatility.

The IC in the figure is a Fairchild Semiconductor CD4000-series circuit, suitable for supplies of 3 to 15V, but it could also be a 74AC14 or 74HC14 from NXP, for example. Any CMOS-input gate having a Schmitt-trigger action is suitable. You must take care to bias the inputs in the middle of their hysteresis range. HCMOS circuits would require an average bias of approximately 1.2V for a 5V supply, for example.

About the author
Louis Vlemincq contributed this article.

This article is a Design Idea selected for re-publication by the editors. It was first published on September 4, 2008 in

Want to more of this to be delivered to you for FREE?

Subscribe to EDN Asia alerts and receive the latest design ideas and product news in your inbox.

Got to make sure you're not a robot. Please enter the code displayed on the right.

Time to activate your subscription - it's easy!

We have sent an activate request to your registerd e-email. Simply click on the link to activate your subscription.

We're doing this to protect your privacy and ensure you successfully receive your e-mail alerts.

Add New Comment
Visitor (To avoid code verification, simply login or register with us. It is fast and free!)
*Verify code:
Tech Impact

Regional Roundup
Control this smart glass with the blink of an eye
K-Glass 2 detects users' eye movements to point the cursor to recognise computer icons or objects in the Internet, and uses winks for commands. The researchers call this interface the "i-Mouse."

GlobalFoundries extends grants to Singapore students
ARM, Tencent Games team up to improve mobile gaming

News | Products | Design Features | Regional Roundup | Tech Impact