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.
supply it with a voltage divider? the supply current is quite low
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
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.
ADCMP350 has an internal 0.6V reference. So a 17.2K/1K divider would get you a 10.92V nominal threshold.
Over 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.
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.
I’ve seen a couple of vendors recently release higher voltage supervisors up to 40v
Check ROHM BD48HW0G etc ?
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.
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.
ADCMP350 has an internal 0.6V reference. So a 17.2K/1K divider would get you a 10.92V nominal threshold.
Over 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.
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ADCMP350 $1.60
Chip resistors are $0.10 each and you need three.
Total cost $1.90
TPS3847108DBVR 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 $0.53
MIC833YM5 $0.66
The Digi-Key and Mauser search engines are your friend.
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.
...
Mouser 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.