LPC MicrocontrollersのトピックRe: Any speed limit at VDDreg = 2.2V?

Any speed limit at VDDreg = 2.2V?

lpcware — Wed, 15 Jun 2016 18:55:42 GMT

Content originally posted in LPCWare by mark03 on Mon Oct 15 15:44:17 MST 2012
Usually an MCU's maximum clock speed is somewhat voltage dependent, but I cannot find any indication of this in the LPC43xx datasheets. Is operation up to 208 MHz supported at the stated minimum VDDreg of 2.2 volts?

I'm also pondering how to connect Vbat in my system. I will have a Li-ion battery which can exceed the max allowed Vbat (max battery 4.2, max Vbat 3.6). Would an acceptable solution be to connect the battery directly through a large-value resistor R, such that (4.2-3.6)/R is comparable to the stated Vbat current of 2 microamps? If the current requirement is relatively constant, this would still present 2.4 volts at the Vbat pin when the battery was empty at 3 volts.

Re: Any speed limit at VDDreg = 2.2V?

lpcware — Wed, 15 Jun 2016 18:55:43 GMT

Content originally posted in LPCWare by mark03 on Mon Oct 15 15:45:29 MST 2012
Oops, make that 204 MHz.

Re: Any speed limit at VDDreg = 2.2V?

lpcware — Wed, 15 Jun 2016 18:55:44 GMT

Content originally posted in LPCWare by Pacman on Tue Oct 16 10:33:25 MST 2012
I don't know the answer to the max. clock-speed at 204MHz (I've tried looking in the UM, but so far I found no information on this topic).

But regarding the battery question... How about one or two 4148 diodes in series; there's a voltage-drop of 0.6V..0.7V on a diode, so if you put two in series, you'd be 'safe' on 3V.

Love
Jens

Re: Any speed limit at VDDreg = 2.2V?

lpcware — Wed, 15 Jun 2016 18:55:44 GMT

Content originally posted in LPCWare by mark03 on Tue Oct 16 13:49:38 MST 2012
Hi Jens,

I thought about a diode, but if you look at the forward voltage at 2 uA current, it is actually very small (much much less than 0.7 volts).

I'm still waiting for an NXP rep to answer my first question. It's something they have to know, and something the community couldn't possibly know. So hello, NXP?? I know you're reading this :)

Re: Any speed limit at VDDreg = 2.2V?

lpcware — Wed, 15 Jun 2016 18:55:45 GMT

Content originally posted in LPCWare by mark03 on Thu Oct 18 09:34:41 MST 2012
I am still waiting. NXP, where are you?

Re: Any speed limit at VDDreg = 2.2V?

lpcware — Wed, 15 Jun 2016 18:55:46 GMT

Content originally posted in LPCWare by tha on Thu Oct 18 16:16:43 MST 2012
From the datasheet:
"Single 3.3 V (2.2 V to 3.6 V) power supply with on-chip DC-to-DC converter for the
core supply and the RTC power domain."

This means the core is power from the internal regulator. So as long as the VDDreg is within spec, the internal regulator would maintain the optimal voltage for the core. Thus, even at the minimum 2.2V, 208MHz is still attainable.

Re: Any speed limit at VDDreg = 2.2V?

lpcware — Wed, 15 Jun 2016 18:55:46 GMT

Content originally posted in LPCWare by mark03 on Fri Oct 19 12:19:43 MST 2012
tha,

I wondered if that might be the case, but it isn't entirely clear from the datasheet. For one thing, claiming that there is a "DC-to-DC converter" on the chip is pretty strange. Surely they mean a linear regular instead? I don't think they have an inductor on the die :)

In any case, I would really have appreciated confirmation from an actual NXP representative. I find it astonishing that they would set up a forum like this and then not answer such obvious, simple, and direct questions. Compare this to the Energy Micro forums, where an employee responds to each question within a day, usually less. (And some of those questions are clueless newbies who you could at least imagine ignoring or pointing to the user's guide.) NXP really needs to up their game, otherwise as soon as a comparable M4F solution is available from a mfg with better customer support, I won't look back.

The many posts here pointing out mistakes in the official libraries, and typos in the documentation, almost always go without any acknowledgement from NXP. If they can't be bothered to have one or two employees monitor the forums, how much effort do you think they're actually spending to fix those bugs/typos/errata? This does not bode well for the future of their parts.

(Case in point: Look at the posts by user "gregd". Carefully written, well informed, and deserving of a response from NXP, yet they usually get zero replies. There is no conceivable excuse for this.)

Re: Any speed limit at VDDreg = 2.2V?

lpcware — Wed, 15 Jun 2016 18:55:47 GMT

Content originally posted in LPCWare by Jg on Tue Oct 23 15:01:55 MST 2012
I can confirm the part contains an internal regulator. The 204 MHz holds for the complete VDDREG range of 2.2-3.6V.