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Discussion Groups | LPC900 | Re: Digest Number 63
Find help, specifications and source code for the LPC900. The LPC900 challenges Microchip and AVR based on the worlds most popular 8-bit architecture the 80C51. With a 2-clock core the LPC900 series is a high performance, very flexible and low cost 8-bit microcontroller family. Designers using or interested in these devices are encouraged to share their know-how and ask questions.
Re: Digest Number 63 - Pragnesh Sheth - Apr 2 6:46:00 2005
Hello Robert,
I tried earlier but it did not work.
If I put Large capcitor on power supply it will increase both
raise and fall time of power supply.
If raise time is slow will it not effect reset ckt.
Pragnesh >Message: 2
> Date: Fri, 01 Apr 2005 20:04:03 -0000
> From: "philips_apps" <philips_apps@phil...>
> Subject: Re: LPC FLASH WRITE ON POWERFAIL > Hello Pragnesh,
>
> this is a food and very important question and the answer is depending
> on some of your system paramters.
>
> 1. You can generate an interrupt only for the higher Brown out trip
> point which is between 2.7 and 2.4 Volt. There is a lower trip point
> below 2.4V that offer reset only as event when it gets triggered. In
> our tests the trip point for the higher BOD is very close to 2.5V when
> the voltage is going down. You can write to the internal flash while
> you are working within the specified voltages which are 2.4 - 3.6 V
>
> 2. How long you will be operating between the trip point and 2.4V,
> that depends highly on your capacitors of the power supply. Check the
> ramp down voltage of your supply and if you find out you have 10 ms
> between 2.4 and 2.5V that gives you a few write cycles, however, if it
> is only 1 ms that is too short.
>
> 3. You could actually use the comparator with the internal reference
> voltage combined with an external resistor divider to find out earlier
> about your power going away if you are using a voltage regulator.
>
> 4. It depends most about your power source. Running from a battery,
> you will have hours or probably day / weeks below the trip point of
> the interrupt and the actual power fail, running from a small voltage
> regulator connected to AC and not much capacitors on board it might
> only by a millisecond.
>
> Hope this helps you to answer your question for your specific
> environment.
>
> Regards, Robert
(You need to be a member of LPC900_users -- send a blank email to LPC900_users-subscribe@yahoogroups.com )
I tried earlier but it did not work.
If I put Large capcitor on power supply it will increase both
raise and fall time of power supply.
If raise time is slow will it not effect reset ckt.
Pragnesh >Message: 2
> Date: Fri, 01 Apr 2005 20:04:03 -0000
> From: "philips_apps" <philips_apps@phil...>
> Subject: Re: LPC FLASH WRITE ON POWERFAIL > Hello Pragnesh,
>
> this is a food and very important question and the answer is depending
> on some of your system paramters.
>
> 1. You can generate an interrupt only for the higher Brown out trip
> point which is between 2.7 and 2.4 Volt. There is a lower trip point
> below 2.4V that offer reset only as event when it gets triggered. In
> our tests the trip point for the higher BOD is very close to 2.5V when
> the voltage is going down. You can write to the internal flash while
> you are working within the specified voltages which are 2.4 - 3.6 V
>
> 2. How long you will be operating between the trip point and 2.4V,
> that depends highly on your capacitors of the power supply. Check the
> ramp down voltage of your supply and if you find out you have 10 ms
> between 2.4 and 2.5V that gives you a few write cycles, however, if it
> is only 1 ms that is too short.
>
> 3. You could actually use the comparator with the internal reference
> voltage combined with an external resistor divider to find out earlier
> about your power going away if you are using a voltage regulator.
>
> 4. It depends most about your power source. Running from a battery,
> you will have hours or probably day / weeks below the trip point of
> the interrupt and the actual power fail, running from a small voltage
> regulator connected to AC and not much capacitors on board it might
> only by a millisecond.
>
> Hope this helps you to answer your question for your specific
> environment.
>
> Regards, Robert
(You need to be a member of LPC900_users -- send a blank email to LPC900_users-subscribe@yahoogroups.com )