I have a requirement were I need to get a processor up and running very quickly. 10ms in fact. Most power on reset circuits have a large variation on reset time of 5 to 15ms. I am looking for something that is accurate to say 20% and simple and cheap. Threshold of around 2.7V. I do have a 32kHz clock that appears when power above 2.8V which could possible be used, any ideas would be appreciated.
Accurate fast start up power on reset
Started by ●December 7, 2015
Reply by ●December 7, 20152015-12-07
steve wrote:> I have a requirement were I need to get a processor up and running very quickly. 10ms in fact. Most power on reset circuits have a large variation on reset time of 5 to 15ms. I am looking for something that is accurate to say 20% and simple and cheap. Threshold of around 2.7V. I do have a 32kHz clock that appears when power above 2.8V which could possible be used, any ideas would be appreciated.10ms from what? A power supply being plugged in? A physical power switch being turned on? A wake-on-LAN message? And how quickly are your power supplies going to go from 0 to ready? I ask because all that stuff bakes in additional ambiguity. ESPECIALLY anything mechanical, which might chatter for milliseconds just on its own. Speaking of mechanical things, how reliable is the start time of your 32 kHz clock? If this requirement really is managable, I'm going to guess that your best answer will be something with a shunt VREF, an open-drain comparator, and an RC. The LM393 predates cave paintings, but is dirt cheap and a fine choice for this; half to make a ramp and half to square it up.
Reply by ●December 7, 20152015-12-07
Den mandag den 7. december 2015 kl. 11.43.29 UTC+1 skrev steve:> I have a requirement were I need to get a processor up and running very quickly. 10ms in fact. Most power on reset circuits have a large variation on reset time of 5 to 15ms. I am looking for something that is accurate to say 20% and simple and cheap. Threshold of around 2.7V. I do have a 32kHz clock that appears when power above 2.8V which could possible be used, any ideas would be appreciated.ldo with a powergood output ? -Lasse
Reply by ●December 8, 20152015-12-08
steve wrote:> I have a requirement were I need to get a processor up and running very quickly. 10ms in fact. Most power on reset circuits have a large variation on reset time of 5 to 15ms. I am looking for something that is accurate to say 20% and simple and cheap. Threshold of around 2.7V. I do have a 32kHz clock that appears when power above 2.8V which could possible be used, any ideas would be appreciated.1) Use a 555 for turn-on timing. Simplest and least expensive. Power on signal can be microseconds after threshold. 2) Have that oscillator run a ripple counter, say divide by at least 16 (the oscillator is doing half of the work,the divide by 16 ensures the oscillator is stable. Power on signal would be 0.5mSec after oscillator on at divide by 16, 1.0mSec delay at divide by 32,etc.
Reply by ●December 8, 20152015-12-08
On Monday, December 7, 2015 at 5:03:19 PM UTC, Rob Gaddi wrote:> steve wrote: > > > I have a requirement were I need to get a processor up and running very quickly. 10ms in fact. Most power on reset circuits have a large variation on reset time of 5 to 15ms. I am looking for something that is accurate to say 20% and simple and cheap. Threshold of around 2.7V. I do have a 32kHz clock that appears when power above 2.8V which could possible be used, any ideas would be appreciated. > > 10ms from what? A power supply being plugged in? A physical power > switch being turned on? A wake-on-LAN message? And how quickly are > your power supplies going to go from 0 to ready? > > I ask because all that stuff bakes in additional ambiguity. ESPECIALLY > anything mechanical, which might chatter for milliseconds just on its > own. Speaking of mechanical things, how reliable is the start time of > your 32 kHz clock? > > If this requirement really is managable, I'm going to guess that your > best answer will be something with a shunt VREF, an open-drain > comparator, and an RC. The LM393 predates cave paintings, but is dirt > cheap and a fine choice for this; half to make a ramp and half to > square it up.10ms from the 3V rail reaching 2.7V, the 32KHz clock is from an RTC chip that is permanently running. Its 32KHz output appears when the power rail hits 2.8V when its switches from battery to 3V power. The psu reaches 2.7V in less than 5ms. An external device triggers the PSU to start up and 30ms later it sends its data to be captured by us. Hoipe that makes sense
Reply by ●December 8, 20152015-12-08
On 12/8/2015 9:54 AM, steve wrote:> On Monday, December 7, 2015 at 5:03:19 PM UTC, Rob Gaddi wrote: >> steve wrote: >> >>> I have a requirement were I need to get a processor up and running very quickly. 10ms in fact. Most power on reset circuits have a large variation on reset time of 5 to 15ms. I am looking for something that is accurate to say 20% and simple and cheap. Threshold of around 2.7V. I do have a 32kHz clock that appears when power above 2.8V which could possible be used, any ideas would be appreciated. >> >> 10ms from what? A power supply being plugged in? A physical power >> switch being turned on? A wake-on-LAN message? And how quickly are >> your power supplies going to go from 0 to ready? >> >> I ask because all that stuff bakes in additional ambiguity. ESPECIALLY >> anything mechanical, which might chatter for milliseconds just on its >> own. Speaking of mechanical things, how reliable is the start time of >> your 32 kHz clock? >> >> If this requirement really is managable, I'm going to guess that your >> best answer will be something with a shunt VREF, an open-drain >> comparator, and an RC. The LM393 predates cave paintings, but is dirt >> cheap and a fine choice for this; half to make a ramp and half to >> square it up. > > 10ms from the 3V rail reaching 2.7V, the 32KHz clock is from an RTC chip that is permanently running. Its 32KHz output appears when the power rail hits 2.8V when its switches from battery to 3V power. The psu reaches 2.7V in less than 5ms. An external device triggers the PSU to start up and 30ms later it sends its data to be captured by us. Hoipe that makes senseJust curious, how much searching did you do? There are tons of reset supervisors out there in small packages and low prices. How about the MAX6394? It has a 2.9 volt version with a 1 to 2 ms timeout. -- Rick
Reply by ●December 9, 20152015-12-09
On Tuesday, December 8, 2015 at 4:38:24 PM UTC, rickman wrote:> On 12/8/2015 9:54 AM, steve wrote: > > On Monday, December 7, 2015 at 5:03:19 PM UTC, Rob Gaddi wrote: > >> steve wrote: > >> > >>> I have a requirement were I need to get a processor up and running very quickly. 10ms in fact. Most power on reset circuits have a large variation on reset time of 5 to 15ms. I am looking for something that is accurate to say 20% and simple and cheap. Threshold of around 2.7V. I do have a 32kHz clock that appears when power above 2.8V which could possible be used, any ideas would be appreciated. > >> > >> 10ms from what? A power supply being plugged in? A physical power > >> switch being turned on? A wake-on-LAN message? And how quickly are > >> your power supplies going to go from 0 to ready? > >> > >> I ask because all that stuff bakes in additional ambiguity. ESPECIALLY > >> anything mechanical, which might chatter for milliseconds just on its > >> own. Speaking of mechanical things, how reliable is the start time of > >> your 32 kHz clock? > >> > >> If this requirement really is managable, I'm going to guess that your > >> best answer will be something with a shunt VREF, an open-drain > >> comparator, and an RC. The LM393 predates cave paintings, but is dirt > >> cheap and a fine choice for this; half to make a ramp and half to > >> square it up. > > > > 10ms from the 3V rail reaching 2.7V, the 32KHz clock is from an RTC chip that is permanently running. Its 32KHz output appears when the power rail hits 2.8V when its switches from battery to 3V power. The psu reaches 2.7V in less than 5ms. An external device triggers the PSU to start up and 30ms later it sends its data to be captured by us. Hoipe that makes sense > > Just curious, how much searching did you do? There are tons of reset > supervisors out there in small packages and low prices. > > How about the MAX6394? It has a 2.9 volt version with a 1 to 2 ms > timeout. > > -- > > RickRick I need 10 ms +/- 20%, this chip does 14ms min 28ms max which is the usual problem of a 3:1 min to max ratio
Reply by ●December 9, 20152015-12-09
On 9.12.15 14:02, steve wrote:> On Tuesday, December 8, 2015 at 4:38:24 PM UTC, rickman wrote: >> On 12/8/2015 9:54 AM, steve wrote: >>> On Monday, December 7, 2015 at 5:03:19 PM UTC, Rob Gaddi wrote: >>>> steve wrote: >>>> >>>>> I have a requirement were I need to get a processor up and running very quickly. 10ms in fact. Most power on reset circuits have a large variation on reset time of 5 to 15ms. I am looking for something that is accurate to say 20% and simple and cheap. Threshold of around 2.7V. I do have a 32kHz clock that appears when power above 2.8V which could possible be used, any ideas would be appreciated. >>>> >>>> 10ms from what? A power supply being plugged in? A physical power >>>> switch being turned on? A wake-on-LAN message? And how quickly are >>>> your power supplies going to go from 0 to ready? >>>> >>>> I ask because all that stuff bakes in additional ambiguity. ESPECIALLY >>>> anything mechanical, which might chatter for milliseconds just on its >>>> own. Speaking of mechanical things, how reliable is the start time of >>>> your 32 kHz clock? >>>> >>>> If this requirement really is managable, I'm going to guess that your >>>> best answer will be something with a shunt VREF, an open-drain >>>> comparator, and an RC. The LM393 predates cave paintings, but is dirt >>>> cheap and a fine choice for this; half to make a ramp and half to >>>> square it up. >>> >>> 10ms from the 3V rail reaching 2.7V, the 32KHz clock is from an RTC chip that is permanently running. Its 32KHz output appears when the power rail hits 2.8V when its switches from battery to 3V power. The psu reaches 2.7V in less than 5ms. An external device triggers the PSU to start up and 30ms later it sends its data to be captured by us. Hoipe that makes sense >> >> Just curious, how much searching did you do? There are tons of reset >> supervisors out there in small packages and low prices. >> >> How about the MAX6394? It has a 2.9 volt version with a 1 to 2 ms >> timeout. >> >> -- >> >> Rick > > Rick I need 10 ms +/- 20%, this chip does 14ms min 28ms max which is the usual problem of a 3:1 min to max ratioWhat prevents you from being ready before 10ms - 20% ? -- -TV
Reply by ●December 9, 20152015-12-09
On 09.12.2015 г. 14:02, steve wrote:> On Tuesday, December 8, 2015 at 4:38:24 PM UTC, rickman wrote: >> On 12/8/2015 9:54 AM, steve wrote: >>> On Monday, December 7, 2015 at 5:03:19 PM UTC, Rob Gaddi wrote: >>>> steve wrote: >>>> >>>>> I have a requirement were I need to get a processor up and running very quickly. 10ms in fact. Most power on reset circuits have a large variation on reset time of 5 to 15ms. I am looking for something that is accurate to say 20% and simple and cheap. Threshold of around 2.7V. I do have a 32kHz clock that appears when power above 2.8V which could possible be used, any ideas would be appreciated. >>>> >>>> 10ms from what? A power supply being plugged in? A physical power >>>> switch being turned on? A wake-on-LAN message? And how quickly are >>>> your power supplies going to go from 0 to ready? >>>> >>>> I ask because all that stuff bakes in additional ambiguity. ESPECIALLY >>>> anything mechanical, which might chatter for milliseconds just on its >>>> own. Speaking of mechanical things, how reliable is the start time of >>>> your 32 kHz clock? >>>> >>>> If this requirement really is managable, I'm going to guess that your >>>> best answer will be something with a shunt VREF, an open-drain >>>> comparator, and an RC. The LM393 predates cave paintings, but is dirt >>>> cheap and a fine choice for this; half to make a ramp and half to >>>> square it up. >>> >>> 10ms from the 3V rail reaching 2.7V, the 32KHz clock is from an RTC chip that is permanently running. Its 32KHz output appears when the power rail hits 2.8V when its switches from battery to 3V power. The psu reaches 2.7V in less than 5ms. An external device triggers the PSU to start up and 30ms later it sends its data to be captured by us. Hoipe that makes sense >> >> Just curious, how much searching did you do? There are tons of reset >> supervisors out there in small packages and low prices. >> >> How about the MAX6394? It has a 2.9 volt version with a 1 to 2 ms >> timeout. >> >> -- >> >> Rick > > Rick I need 10 ms +/- 20%, this chip does 14ms min 28ms max which is the usual problem of a 3:1 min to max ratio >If you cannot find a single chip to do that do it in two chips, say one of those no-timer "power good" detectors and a 555 or a 74hc123 or something. Will take some passives but I guess this is the price to pay for the accuracy you are after. Typically no one cares about another 10 or 100 ms longer time reset being held active, e.g. I had to look in the datasheet of the part I have been using for years to check if it would work for you (it would not). BTW those readily available one chip parts are fine as long as you use them as specified. Many years ago I used a Maxim part and strayed a little - made some assumptions about unspecified behaviour - and *all* my assumptions proved wrong... I ended up removing the part on the second board revision and doing things myself somehow (don't remember, was 20+ years ago), adapting to the single chip like I did on the first revision was more pain than that. Dimiter ------------------------------------------------------ Dimiter Popoff Transgalactic Instruments http://www.tgi-sci.com ------------------------------------------------------ http://www.flickr.com/photos/didi_tgi/
Reply by ●December 9, 20152015-12-09
On 07/12/2015 10:43, steve wrote:> I have a requirement were I need to get a processor up and running very quickly. 10ms in fact. Most power on reset circuits have a large variation on reset time of 5 to 15ms. I am looking for something that is accurate to say 20% and simple and cheap. Threshold of around 2.7V. I do have a 32kHz clock that appears when power above 2.8V which could possible be used, any ideas would be appreciated. >A PIC10F320 will run from 2V to 5.5V and has an ADC, a voltage reference, and an accurate internal oscillator which wakes up in a few microseconds. The rest is firmware. Cheers -- Syd
