another timer ic alternative - Page 1
Forum section: electronics / beginners

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: March 10, 2019, 07:47:42 am
content: Are there other ICs with similar features to the ltc6991?Particularly precision long duration timing with with only a few resistors.

author: beanflying
author_rank: Super Contributor
timestamp: March 10, 2019, 08:01:50 am
content: Way to many unknowns in your request.Define 'Precision' and 'Long Term' and maybe a budget? Are you on a power budget/batteries? Even tell us your applicationOtherwise you will not get the answer you want. One alternate you can look at in the meantime is one of the UBlox GPS receivers depending on your answers to the above info request.

author: oPossum
author_rank: Super Contributor
timestamp: March 10, 2019, 08:29:57 am
content: 74HC555574HC4060PIC10F200

author: Zero999
author_rank: Super Contributor
timestamp: March 10, 2019, 05:45:18 pm
content: CD4536CD4541ICM7242ATTINY9-TS8R.

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: March 10, 2019, 07:57:52 pm
content: Quote from: beanflying on March 10, 2019, 08:01:50 amPrecision of a crystal oscillator into a 4060 4040 combo.CD4536, CD4541, ICM7242 all use timer capacitor which is inaccurate. There are no crystals under 20khz unless you dig for ancient large wafer crystals which don't have easy replacement parts.It seems crystal and 4060+4040 combo is still the least expensive.

author: malagas_on_fire
author_rank: Frequent Contributor
timestamp: March 10, 2019, 08:04:19 pm
content: Check if this may help you:https://www.embedded.com/electronics-blogs/without-a-paddle/4440409/Timer--anyone--

author: Zero999
author_rank: Super Contributor
timestamp: March 10, 2019, 10:58:50 pm
content: Quote from: LaserTazerPhaser on March 10, 2019, 07:57:52 pmI believe it's possible to use the CD4536 with a crystal. According to the data sheet, it has the same oscillator circuit as the CD4060. I'm not sure about the CD4541. Failing that, add one of the aforementioned to the CD4060, for much longer delays. In any case, the problem with crystals is the limited number of frequencies available.http://www.ti.com/lit/ds/symlink/cd4536b.pdfhttp://www.ti.com/lit/ds/symlink/cd4060b.pdfThe LTC6991 is also an RC oscillator, which is only 1.5% accurate. A microcontroller can do better than that using its internal RC oscillator, with an accuracy of typically 1%.

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: March 11, 2019, 12:52:38 am
content: Quote from: Zero999 on March 10, 2019, 10:58:50 pmltc6991 is entirely resistor programmed.http://beta-tools.analog.com/timerblox/LTC6991

author: beanflying
author_rank: Super Contributor
timestamp: March 11, 2019, 01:05:04 am
content: Have a look at the TCXO Maxim Range in this parametric search for some options. External parts count looks low for most of them.https://para.maximintegrated.com/en/search.mvp?fam=rtc&270=TCXO

author: Zero999
author_rank: Super Contributor
timestamp: March 11, 2019, 09:18:49 am
content: Quote from: LaserTazerPhaser on March 11, 2019, 12:52:38 amHmm, the data sheet says it has a "silicon oscillator" which I couldn't find much about using Google. Some hits talk about MEMS, but given the frequency is adjustable by selecting an external resistor and the tolerance is only 1.5%, I suspect it's just an RC oscillator with an on chip precision capacitor.In any case, 1.5% accuracy is doable with an RC oscillator. Use a 1% tolerance resistor and a ceramic capacitor with a C0G dialectic. The trouble is, the CD4536, CD4541, CD4060.74HC5555might not give that degree if accuracy, even with a close tolerance RC circuit. The ICM7242 might be better, an external comparator oscillator, better still.https://uk.rs-online.com/web/p/ceramic-multilayer-capacitors/7236398/https://www.digikey.com/product-detail/en/murata-electronics-north-america/GRM2165C1H222FA01D/490-6443-1-ND/3845640EDIT:The 74HC5555 has a tolerance of <1%, see page 21 of the data sheet. Follow the design guidelines, using a 0.5% tolerance resistor and 1% tolerance capacitor and it will be better than the LTC6991.https://assets.nexperia.com/documents/data-sheet/74HC5555.pdf

author: aorcan
author_rank: Newbie
timestamp: January 03, 2021, 05:02:21 pm
content: There are several Programmable Timer IC's such as CD4536 capable of 2 ~ 2²⁴ counts/cycle and up to a few MHz operation. Note that, with CD4536 in its programmable mode, counts can be only up to 2^16. For accuracy, crystals, with the internal oscillator can be used or a TXCO can be used. I like using 32.768kHz 20-100ppm/deg resonators or 4.43MHz 10ppm crystals to get multiples of 1 second. In timers, oscillator frequency can be a few kHz to a few MHz, but at higher frequencies supply Voltages have to be be increased within upper operating limits of the IC's. Data sheets such ashttps://www.ti.com/lit/ds/symlink/cd4536b.pdf?HQS=dis-dk-null-digikeymode-dsf-pf-null-wwe&ts=1609665732070include all the required info. Use of microcontrollers IMHO is not necessary as using a CD4536 or a similar device costs very little and is quicker without any need for programming. Further additions such as adjustable pulse duration one-shots, compounded timers. remedies against power failures are just a few possibilities.

author: Zero999
author_rank: Super Contributor
timestamp: January 03, 2021, 09:45:34 pm
content: I've had a bad experience with Linear's TimerBlox ICs, the LTC6994-2, and don't know why anyone would use one, over a microcontroller. Two of them failed, out of a batch of 180. They weren't run at excessive temperatures, they were operated well within their ratings and none of their inputs or outputs were connected to the outside world, but to other logic gates and comparators, run off the same stable 5V rail. It was not my design, but that of an external contractor, before I joined the company.

author: srb1954
author_rank: Super Contributor
timestamp: January 04, 2021, 08:41:10 am
content: Quote from: LaserTazerPhaser on March 10, 2019, 07:57:52 pmStatek make tuning fork crystals down to 10kHz in a small SMD package (8.0 x 3.6mm). These are electrically quite delicate and can be fractured by excessive drive levels so careful attention is required to the design of the oscillator circuitry.