| ??? 08/10/05 16:21 Read: times |
#99133 - Could 3V devices have these problems? Responding to: ???'s previous message |
Tomas,
Thanks for your valuable comment. The result was very unreliable resets (most would reset fine..some would result in a lockup). It wasn't a problem that most would notice during development, however. It was only obvious once we sat there power cycling on the final PCB 100's of times. Bill, Lets start life with Vdd= 0. When Vdd RAMPS from 0 to 0.2V a power-on detect (POD) circuit goes active and holds the part in reset(POR). When should it let go of reset? As Vdd continues to ramp, eventually the brownout detect(BOD)circuits work.... Your insight in the power on sequence is quite revealing, but dont the other flash micrcontrollers which we now use for our regular production go through the same power up sequence, and do not face the problems which the LPC9xxx seem to be having. ...This can cause an unintended erase/program operation on a part with IAP. A product with P89C51xxx with IAP, works under similar conditions and face the similar power up sequence, but I have not come accross inadvertent flash corruption. Prahlad, This kind of issues have been discussed many times. The on chip brown out and resets do have serious limitations. Not so! I have to disagree with you on the above point. I have been working with other microcontrollers with built in power on reset and brown out reset (produced 100's of them), and they are working without any problems, also I have never produced a microcontroller product without a supervisor, I have been using a supervisor since 1989 from the time I made my first SBC. It was a good thing for micro manufacturers to incorporate the POR and BOR inside the micro to save cost, then what is the point in having this in the LPC9xxx micros, when their competitor (5Volt)parts are working without any problem. I read Bill's and your posts carefully but I still cant understand why an external supervisor such as MAX809 that can provide reset down to 0V wont solve the problems with chip. If the supply voltage is below threshhold the external supervisor will hold micro under reset. Pleae explain more on this. To me solving the (reset) problem with an external reset, is not the main issue (there are exotic supervisors available now), if the manufacturers claimed POR and BOR is not functioning, then the very idea of low pin count low cost is defeated. Promod, All the LPC932 devices I lost were after handling them. So, use proper Static Handling procedures. You are probably destroying / locking up your chips because of this. Thanks for your advice, as we are already manufacturing products using static sensitive micros, we are aware of the static issues, maybe the LPC9xx require more care in handling than other regular micros? Even with all these issues I would still like to implement the LPC9xxx series in my products, if someone who has produced 100's of these can share their valuable experience It will be great. I have not studied the LPC9xxx against a 3Volt competitors part, we will have to find out whether other micros such as the Silabs micros with 3V has similar flash corruption / reset issues. Regards, John. |
