Suggestions for 12V voltage supervisor IC? - Page 1
Forum section: electronics / projects

author: HwAoRrDk
author_rank: Super Contributor
timestamp: May 15, 2024, 04:03:44 pm
content: Can anyone give any suggestions for a simple, cheap voltage detector/supervisor chip that has a threshold of around 10.8-11.0V?Something similar to the classic jellybean MAX809 and siblings, but all those only have thresholds at most up to about 6 or 7 volts.I want to be able to assert an active-low reset signal if the +12V supply voltage drops out lower than around 10%. Preferably with an open-drain output.

author: langwadt
author_rank: Super Contributor
timestamp: May 15, 2024, 04:34:13 pm
content: supply it with a voltage divider? the supply current is quite low

author: youngda9
author_rank: Regular Contributor
timestamp: May 15, 2024, 05:16:10 pm
content: You can just use a comparator for this application. Many have an internal reference internal already. ADCMP350 would be a great option.https://www.digikey.com/en/products/detail/analog-devices-inc/ADCMP350YKSZ-REEL7/995325ADCMP350 has an internal 0.6V reference. So a 17.2K/1K divider would get you a 10.92V nominal threshold.

author: hlab
author_rank: Contributor
timestamp: May 15, 2024, 05:45:42 pm
content: Just use a micropower supervisor such as a TLV803E, powered from resistor divider that brings it down to a lower voltage. Relatively cheap, readily available, accurate, and small

author: HwAoRrDk
author_rank: Super Contributor
timestamp: May 15, 2024, 05:55:46 pm
content: Yes, I could use a voltage divider, but I was hoping for a single-component solution.The only thing I've found myself is the TI TPS3847108 (10.8V threshold), which is good in that it has a /MR pin to pass through a master reset (so open-drain output not so important), but is super expensive.Maybe such higher-voltage supervisors just generally don't exist, and I'll have to use an external divider with a jellybean supervisor.Quote from: youngda9 on May 15, 2024, 05:16:10 pmOver a dollar each?! No thanks, I'll pass. And if I have to use a voltage divider, I might as well use one of the cheap, ubiquitous, dedicated ICs.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: May 15, 2024, 07:31:25 pm
content: Quote from: HwAoRrDk on May 15, 2024, 04:03:44 pmI’ve seen a couple of vendors recently release higher voltage supervisors up to 40vCheck ROHM BD48HW0G etc ?

author: hlab
author_rank: Contributor
timestamp: May 15, 2024, 07:32:25 pm
content: Another benefit to the jellybean supervisors is that they typically guarantee a minimum reset pulse width. A simple comparator might not have a fast enough slew rate in the case a really fast power glitch.

author: MarkL
author_rank: Unknown
timestamp: May 15, 2024, 07:40:16 pm
content: How about TL7712A?http://www.ti.com/product/tl7712a

author: selcuk
author_rank: Frequent Contributor
timestamp: May 15, 2024, 08:15:30 pm
content: SP706T / SP708T may provide a different approach if suitable for your circuit. VCC supervisory input is for 3.3V CPU supply. There is also a PFI input to monitor 12V via voltage divider resistors. Then you may connect the PFO output to the CPU interrupt. This way CPU can detect power loss before getting reset. There is also a MR input for external reset sources.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: May 15, 2024, 09:23:20 pm
content: Quote from: HwAoRrDk on May 15, 2024, 05:55:46 pmThey are certainly less common that the high volume sub 6V parts, but there are more being released.They will always be a higher price than the lower spec parts.More examples herehttps://www.nisshinbo-microdevices.co.jp/en/products/reset-voltage-detector/Their R3119 series seem to be availableAn alternative, is to go for higher voltage, high volume parts like these designed for SMPS feedbackhttps://www.diodes.com/products/power-management/ac-dc-converters/secondary-side-controllers-and-switchers/Those have a VREF and opAmps, so you can make your own detector. 18-40V rated.

author: youngda9
author_rank: Regular Contributor
timestamp: May 16, 2024, 04:58:21 pm
content: Quote from: youngda9 on May 15, 2024, 05:16:10 pmOver a dollar each?! No thanks, I'll pass. And if I have to use a voltage divider, I might as well use one of the cheap, ubiquitous, dedicated ICs.ADCMP350 $1.60Chip resistors are $0.10 each and you need three.Total cost $1.90TPS3847108DBVR costs $2.70 each.TL7712A costs $1.03 each and you need 2 external resistors and 2 external capacitors. So not going to save any money going this rouge.Might as well go with the a comparator based design since it provides more design flexibility, allowing you to adjust the desired threshold and have the output pulled up to different power rails.If cost is an issue...there are also many similar parts, starting at $0.53 that are equivalent to the comparator option.MCP65R41T $0.53MIC833YM5 $0.66The Digi-Key and Mauser search engines are your friend.

author: MarkL
author_rank: Unknown
timestamp: May 16, 2024, 06:40:57 pm
content: Quote from: youngda9 on May 16, 2024, 04:58:21 pmMouser price is $0.70 for the TL7712AIDR, industrial temp range -40C to 85C, cut tape. Not sure why the TL7712ACD commercial 0C to 70C in a tube is more at $1.03. Packaging maybe?By the time you're done with a comparator solution, you're going to need some resistors and capacitors anyway. If you're price shopping, try one of the chip search engines like octopart.com or findchips.com. Arrow has the TL7712AIDR for $0.49. Good luck.EDIT: Fixed price typo.