uC favorites?

B

Bob Stephens

Guest
I am currently using a Silicon Labs (Cygnal) 8051 derivative -C8051F060 -
in an prototype embedded design. I am looking for a replacement device for
future revisions which would have most or all of the following:

8 or 16 bit architecture
4 or more 8 bit +/- 25 mA ports
2 16 bit 1 Msps A/D
2 or more 10 bit 200 Ksps A/D
2 12 bit DAC
2 USART
I2C
SPI
4 or more counter/timers
Low power modes w/wakeup via USART interrupt
Good C/Assembler development tools and debugger
JTAG programming interface
Readily available silicon through distributors in prototype and production
quantities
Datasheets which approximate the actual performance of the device

Anyone have any particular favorites they've had good luck with?


TIA

Bob

--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)
 
Bob Stephens wrote:

I am currently using a Silicon Labs (Cygnal) 8051 derivative -C8051F060 -
in an prototype embedded design. I am looking for a replacement device for
future revisions which would have most or all of the following:

8 or 16 bit architecture
4 or more 8 bit +/- 25 mA ports
2 16 bit 1 Msps A/D
2 or more 10 bit 200 Ksps A/D
2 12 bit DAC
2 USART
I2C
SPI
4 or more counter/timers
Low power modes w/wakeup via USART interrupt
Good C/Assembler development tools and debugger
JTAG programming interface
Readily available silicon through distributors in prototype and production
quantities
Datasheets which approximate the actual performance of the device

Anyone have any particular favorites they've had good luck with?
Click to expand...
This looks like a trick question - what's the F060 missing from the
list above ?

16 bit / 1MSPS ADCs in uC are not common things, but you can get
some DSPs with more MSPS and fewer bits.

-jg
 
If you can put all the analog stuff outside
(could be hard to get high speed 16 bit ADC in a micro)
then the AT91RM3400 could be good for the job.

32 bit ARM7 at 66 MHz executing from internal SRAM, loading from ext
dataflash
Multiple I/O
5 x USART
SPI
TWI (I2C compatible)
6 timers
low power

The AT91SAM7A3 will be the flash version of above with some 10 bit ADC.

--
Best Regards,
Ulf Samuelsson ulf@a-t-m-e-l.com
This is a personal view which may or may not be
share by my Employer Atmel Nordic AB


"Bob Stephens" <stephensyomamadigital@earthlink.net> skrev i meddelandet
news:1o17muidqctrt.5ojgmzp2pv8v.dlg@40tude.net...
I am currently using a Silicon Labs (Cygnal) 8051 derivative -C8051F060 -
in an prototype embedded design. I am looking for a replacement device for
future revisions which would have most or all of the following:

8 or 16 bit architecture
4 or more 8 bit +/- 25 mA ports
2 16 bit 1 Msps A/D
2 or more 10 bit 200 Ksps A/D
2 12 bit DAC
2 USART
I2C
SPI
4 or more counter/timers
Low power modes w/wakeup via USART interrupt
Good C/Assembler development tools and debugger
JTAG programming interface
Readily available silicon through distributors in prototype and production
quantities
Datasheets which approximate the actual performance of the device

Anyone have any particular favorites they've had good luck with?


TIA

Bob

--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)
Click to expand...
 
Bob Stephens wrote:

I am currently using a Silicon Labs (Cygnal) 8051 derivative -C8051F060 -
in an prototype embedded design. I am looking for a replacement device for
future revisions which would have most or all of the following:
. . .
2 16 bit 1 Msps A/D
Click to expand...
Good Luck!
 
On Wed, 28 Apr 2004 10:09:54 +1200, Jim Granville wrote:

Bob Stephens wrote:

I am currently using a Silicon Labs (Cygnal) 8051 derivative -C8051F060 -
in an prototype embedded design. I am looking for a replacement device for
future revisions which would have most or all of the following:

8 or 16 bit architecture
4 or more 8 bit +/- 25 mA ports
2 16 bit 1 Msps A/D
2 or more 10 bit 200 Ksps A/D
2 12 bit DAC
2 USART
I2C
SPI
4 or more counter/timers
Low power modes w/wakeup via USART interrupt
Good C/Assembler development tools and debugger
JTAG programming interface
Readily available silicon through distributors in prototype and production
quantities
Datasheets which approximate the actual performance of the device

Anyone have any particular favorites they've had good luck with?

This looks like a trick question - what's the F060 missing from the
list above ?

Primarily the low power consumption and accurate specs...
Click to expand...

--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)
 
On Wed, 28 Apr 2004 00:11:27 +0200, Ulf Samuelsson wrote:

If you can put all the analog stuff outside
(could be hard to get high speed 16 bit ADC in a micro)
then the AT91RM3400 could be good for the job.

32 bit ARM7 at 66 MHz executing from internal SRAM, loading from ext
dataflash
Multiple I/O
5 x USART
SPI
TWI (I2C compatible)
6 timers
low power

The AT91SAM7A3 will be the flash version of above with some 10 bit ADC.
Click to expand...
Yes, I am considering using an outboard ADC. Unfortunately real estate is
at a premium - as usual.

Bob
--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)
 
On Tue, 27 Apr 2004 16:35:51 -0600, mikem wrote:

Bob Stephens wrote:

I am currently using a Silicon Labs (Cygnal) 8051 derivative -C8051F060 -
in an prototype embedded design. I am looking for a replacement device for
future revisions which would have most or all of the following:
. . .
2 16 bit 1 Msps A/D

Good Luck!
Click to expand...
Actually, the Cygnal part (in *Theory*) provides all of these features and
more. If only they were a wee bit more honest in their datasheets...


Bob
--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)
 
Actually, the Cygnal part (in *Theory*) provides all of these features and
more. If only they were a wee bit more honest in their datasheets...


Bob
--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)
Click to expand...
I'm working a lot with Cygnal devices and I'm curious what did you mean by
"If only they were a wee bit more honest in their datasheets..." ?

- Dejan
 
Bob Stephens wrote:
I am currently using a Silicon Labs (Cygnal) 8051 derivative -C8051F060 -
in an prototype embedded design. I am looking for a replacement device for
future revisions which would have most or all of the following:

8 or 16 bit architecture
4 or more 8 bit +/- 25 mA ports
2 16 bit 1 Msps A/D
2 or more 10 bit 200 Ksps A/D
2 12 bit DAC
2 USART
I2C
SPI
4 or more counter/timers
Low power modes w/wakeup via USART interrupt
Good C/Assembler development tools and debugger
JTAG programming interface
Readily available silicon through distributors in prototype and production
quantities
Datasheets which approximate the actual performance of the device

Anyone have any particular favorites they've had good luck with?
Click to expand...
Like the others have said, trying to get a 1 MSPS 16 bit ADC in an MCU
is pretty much like looking for a one legged relay runner. 16 bit ADC
chips in the MSPS range are difficult to make and tend to be a bit
pricey by themselves, I have seen $10 to $30 each depending on INL. To
put two of them in an MCU and keep the total price below $50 would be a
trick.

I am sure you can find all the other features in various MCUs. Check
out the ADI AD7655 and similar parts. I think this TQFP48 is about as
small as you will get. But realize that you won't get 1 MSPS at "low
power". I'm not sure what your issues with the Cygnal part are. I am
sure people here would be interested in the details.

--

Rick "rickman" Collins

rick.collins@XYarius.com
Ignore the reply address. To email me use the above address with the XY
removed.

Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design URL http://www.arius.com
4 King Ave 301-682-7772 Voice
Frederick, MD 21701-3110 301-682-7666 FAX
 
On Wed, 28 Apr 2004 17:47:47 +0200, Dejan Durdenic wrote:

Actually, the Cygnal part (in *Theory*) provides all of these features and
more. If only they were a wee bit more honest in their datasheets...


Bob
--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)

I'm working a lot with Cygnal devices and I'm curious what did you mean by
"If only they were a wee bit more honest in their datasheets..." ?

- Dejan
Click to expand...
The only Cygnal part I have used is the '060 - I can't speak to the rest.
The data sheet specs as regards power consumption, and internal Vref
performance are extremely misleading at best. We are using it in a battery
powered device, and with the analog peripherals running it is an extreme
power hog. Vdd typical with CPU active is stated as 18 mA, "Power supply
Current (each ADC)is given as 4.0 mA typical. Well, I'm measuring around
85mA total for Vdd and AVdd with one converter running. Also "The
independent, temperature stable 1.25 V bandgap voltage reference generator,
with an output buffer amplifier which multiplies the bandgap reference by
2" comes in at about 2.4401 volts except when it's warm or cold or ... and
varies from device to device. I've had to add an external precision Vref to
get any kind of stability out of the converters - not a big deal if planned
up front but a thumping PITA to tack on to a densely packed board after the
fact.
--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)
 
Bob Stephens <stephensyomamadigital@earthlink.net> wrote in message news:<vc0kdgkyxomt$.pswrgw8bn5wk.dlg@40tude.net>...
Actually, the Cygnal part (in *Theory*) provides all of these features and
more. If only they were a wee bit more honest in their datasheets...
Click to expand...
What do you consider to be misleading in the datasheets? Peak
advertizing mips for artificial problems? That is pretty much
common practice. Or is it something else?
 
Bob Stephens wrote:
On Wed, 28 Apr 2004 10:09:54 +1200, Jim Granville wrote:


Bob Stephens wrote:


I am currently using a Silicon Labs (Cygnal) 8051 derivative -C8051F060 -
in an prototype embedded design. I am looking for a replacement device for
future revisions which would have most or all of the following:

8 or 16 bit architecture
4 or more 8 bit +/- 25 mA ports
2 16 bit 1 Msps A/D
2 or more 10 bit 200 Ksps A/D
2 12 bit DAC
2 USART
I2C
SPI
4 or more counter/timers
Low power modes w/wakeup via USART interrupt
Good C/Assembler development tools and debugger
JTAG programming interface
Readily available silicon through distributors in prototype and production
quantities
Datasheets which approximate the actual performance of the device

Anyone have any particular favorites they've had good luck with?

This looks like a trick question - what's the F060 missing from the
list above ?


Primarily the low power consumption and accurate specs...
Click to expand...
Cygnal are at the low end of uA/MHz, so good luck.
Also, I've never seen a data sheet that could not be improved :)
-jg
 
On 28 Apr 2004 12:39:08 -0700, Jeff Fox wrote:

Bob Stephens <stephensyomamadigital@earthlink.net> wrote in message news:<vc0kdgkyxomt$.pswrgw8bn5wk.dlg@40tude.net>...

Actually, the Cygnal part (in *Theory*) provides all of these features and
more. If only they were a wee bit more honest in their datasheets...

What do you consider to be misleading in the datasheets? Peak
advertizing mips for artificial problems? That is pretty much
common practice. Or is it something else?
Click to expand...
<repost of reply to yet another post>

The only Cygnal part I have used is the '060 - I can't speak to the rest.
The data sheet specs as regards power consumption, and internal Vref
performance are extremely misleading at best. We are using it in a battery
powered device, and with the analog peripherals running it is an extreme
power hog. Vdd typical with CPU active is stated as 18 mA, "Power supply
Current (each ADC)is given as 4.0 mA typical. Well, I'm measuring around
85mA total for Vdd and AVdd with one converter running. Also "The
independent, temperature stable 1.25 V bandgap voltage reference generator,
with an output buffer amplifier which multiplies the bandgap reference by
2" comes in at about 2.4401 volts except when it's warm or cold or ... and
varies from device to device. I've had to add an external precision Vref to
get any kind of stability out of the converters - not a big deal if planned
up front but a thumping PITA to tack on to a densely packed board after the
fact.
--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)
 
Bob Stephens wrote:
On Wed, 28 Apr 2004 17:47:47 +0200, Dejan Durdenic wrote:

Actually, the Cygnal part (in *Theory*) provides all of these features and
more. If only they were a wee bit more honest in their datasheets...


Bob
--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)

I'm working a lot with Cygnal devices and I'm curious what did you mean by
"If only they were a wee bit more honest in their datasheets..." ?

- Dejan

The only Cygnal part I have used is the '060 - I can't speak to the rest.
The data sheet specs as regards power consumption, and internal Vref
performance are extremely misleading at best. We are using it in a battery
powered device, and with the analog peripherals running it is an extreme
power hog. Vdd typical with CPU active is stated as 18 mA, "Power supply
Current (each ADC)is given as 4.0 mA typical. Well, I'm measuring around
85mA total for Vdd and AVdd with one converter running. Also "The
independent, temperature stable 1.25 V bandgap voltage reference generator,
with an output buffer amplifier which multiplies the bandgap reference by
2" comes in at about 2.4401 volts except when it's warm or cold or ... and
varies from device to device. I've had to add an external precision Vref to
get any kind of stability out of the converters - not a big deal if planned
up front but a thumping PITA to tack on to a densely packed board after the
fact.
Click to expand...
That is sad to hear. I have not used any of the Cygnal parts, but I had
the impression from others that they were solid, well designed parts.
If you are seeing these problems over a batch of parts, is it possible
that they were not made well? Often internal parameters are not tested
and it is assumed that if the rest of the chip is good, then these
parameters should be good "by design". You might want to contact Cygnal
about it.

One part that I know I have heard good things about on the analog side
is the MSP430 family. They are not 5 volt tolerant, but they seem to
come with a wide variety of peripherals and can run on very, very low
Idd. If you can deal with a 3.3 volt part on your board, this might be
a better choice.

--

Rick "rickman" Collins

rick.collins@XYarius.com
Ignore the reply address. To email me use the above address with the XY
removed.

Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design URL http://www.arius.com
4 King Ave 301-682-7772 Voice
Frederick, MD 21701-3110 301-682-7666 FAX
 
On Wed, 28 Apr 2004 16:35:40 -0400, rickman wrote:

Bob Stephens wrote:

On Wed, 28 Apr 2004 17:47:47 +0200, Dejan Durdenic wrote:

Actually, the Cygnal part (in *Theory*) provides all of these features and
more. If only they were a wee bit more honest in their datasheets...


Bob
--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)

I'm working a lot with Cygnal devices and I'm curious what did you mean by
"If only they were a wee bit more honest in their datasheets..." ?

- Dejan

The only Cygnal part I have used is the '060 - I can't speak to the rest.
The data sheet specs as regards power consumption, and internal Vref
performance are extremely misleading at best. We are using it in a battery
powered device, and with the analog peripherals running it is an extreme
power hog. Vdd typical with CPU active is stated as 18 mA, "Power supply
Current (each ADC)is given as 4.0 mA typical. Well, I'm measuring around
85mA total for Vdd and AVdd with one converter running. Also "The
independent, temperature stable 1.25 V bandgap voltage reference generator,
with an output buffer amplifier which multiplies the bandgap reference by
2" comes in at about 2.4401 volts except when it's warm or cold or ... and
varies from device to device. I've had to add an external precision Vref to
get any kind of stability out of the converters - not a big deal if planned
up front but a thumping PITA to tack on to a densely packed board after the
fact.

That is sad to hear. I have not used any of the Cygnal parts, but I had
the impression from others that they were solid, well designed parts.
If you are seeing these problems over a batch of parts, is it possible
that they were not made well? Often internal parameters are not tested
and it is assumed that if the rest of the chip is good, then these
parameters should be good "by design". You might want to contact Cygnal
about it.

One part that I know I have heard good things about on the analog side
is the MSP430 family. They are not 5 volt tolerant, but they seem to
come with a wide variety of peripherals and can run on very, very low
Idd. If you can deal with a 3.3 volt part on your board, this might be
a better choice.
Click to expand...
Actually, my board is 3.3V. Thanks Rick, I'll take a look at the MSP.
--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)
 
Bob Stephens wrote:

On 28 Apr 2004 12:39:08 -0700, Jeff Fox wrote:


Bob Stephens <stephensyomamadigital@earthlink.net> wrote in message news:<vc0kdgkyxomt$.pswrgw8bn5wk.dlg@40tude.net>...

Actually, the Cygnal part (in *Theory*) provides all of these features and
more. If only they were a wee bit more honest in their datasheets...

What do you consider to be misleading in the datasheets? Peak
advertizing mips for artificial problems? That is pretty much
common practice. Or is it something else?


repost of reply to yet another post

The only Cygnal part I have used is the '060 - I can't speak to the rest.
The data sheet specs as regards power consumption, and internal Vref
performance are extremely misleading at best. We are using it in a battery
powered device, and with the analog peripherals running it is an extreme
power hog. Vdd typical with CPU active is stated as 18 mA, "Power supply
Current (each ADC)is given as 4.0 mA typical. Well, I'm measuring around
85mA total for Vdd and AVdd with one converter running. Also "The
independent, temperature stable 1.25 V bandgap voltage reference generator,
with an output buffer amplifier which multiplies the bandgap reference by
2" comes in at about 2.4401 volts except when it's warm or cold or ... and
varies from device to device. I've had to add an external precision Vref to
get any kind of stability out of the converters - not a big deal if planned
up front but a thumping PITA to tack on to a densely packed board after the
fact.
Click to expand...
That sounds Atypical - you have, of course, asked Cygnal about it ?

Vref stability is a matter for the fine print. ALL Vrefs will differ
from unit to unit, and also vary over temperature.
The key point is, by how much ?

[They quote 2.44V, or 2.43V Typical as Vref, so 'about 2.4401' does not
sound too terrible ? ]

Their spec also says typ 15ppm/'C tempco.
That's not the very best, but Maxim sell plenty of Vrefs worse than
that. Remember this is an ON-CHIP, Vref.

'Best in class' on External Vrefs approaches a few ppm, but they will
cost as much as the smaller uC :)
If the tempco matters, you'd probably also want to do better
than the 1.25% Vref tolerance.
eg : Maxim can give Vref's with 3ppm and 0.04% Cals.


The Icc numbers sound 'way out' - did you check their EVB Icc, and a
number of samples ?
What did Cygnal say ?

I have not used their 060, but their 330 came in right where expected
on Icc.

-jg
 
On Thu, 29 Apr 2004 10:56:05 +1200, the renowned Jim Granville
<no.spam@designtools.co.nz> wrote:
Vref stability is a matter for the fine print. ALL Vrefs will differ
from unit to unit, and also vary over temperature.
The key point is, by how much ?

[They quote 2.44V, or 2.43V Typical as Vref, so 'about 2.4401' does not
sound too terrible ? ]

Their spec also says typ 15ppm/'C tempco.
That's not the very best, but Maxim sell plenty of Vrefs worse than
that. Remember this is an ON-CHIP, Vref.
Click to expand...
An on-chip Vref has the disadvantage that it is at the die temperature
for the micro. No big deal if the micro is running at a couple of mA
and not switching much, but if it is running hot you can get
objectionable (perhaps on cosmetic grounds) drift during warm-up.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
In sci.electronics.design,comp.arch.embedded, Bob Stephens
<stephensyomamadigital@earthlink.net> wrote:


The only Cygnal part I have used is the '060 - I can't speak to the rest.
The data sheet specs as regards power consumption, and internal Vref
performance are extremely misleading at best. We are using it in a battery
powered device, and with the analog peripherals running it is an extreme
power hog. Vdd typical with CPU active is stated as 18 mA, "Power supply
^^^^^^^
Current (each ADC)is given as 4.0 mA typical.
^^^^^^^
Click to expand...

<SOAPBOX,MODE="ON">

<ahem>

DO NOT DESIGN WITH "TYPICAL" VALUES.

Every chip can be at the stated minimum or maximum (whichver is
worst case) and still be within spec. If they don't have a max current
or power condumption spec, then that's bad, because it can pull five
amperes and (as long as everything else functions within guaranteed
specs) still be "within spec."
If there is some minumum or maximum spec that the chip isn't
meeting (as long as there's no asterisk where it says "these are just
approximate, we don't guarantee them" or other such weasel words),
then you can call the manufacturer and say they have defective parts,
and reasonably ask that they be replaced.
OTOH, every data sheet says specs 'may change at any time' so they
might just change the specs when you complain, but if any
manudfacturer did things like that there would be a LOT of people
complaining about it on Usenet and elsewhere,

Bob Pease has given this lecture at least once, I forget if it was
in his ED column or 'live' as part of is National tour ... ISTR he
suggested running white-out down the 'typical' column of data sheets -
regardless, that's a good idea.


Well, I'm measuring around
85mA total for Vdd and AVdd with one converter running. Also "The
independent, temperature stable 1.25 V bandgap voltage reference generator,
with an output buffer amplifier which multiplies the bandgap reference by
2" comes in at about 2.4401 volts except when it's warm or cold or ... and
varies from device to device. I've had to add an external precision Vref to
get any kind of stability out of the converters - not a big deal if planned
up front but a thumping PITA to tack on to a densely packed board after the
fact.
Click to expand...
-----
http://mindspring.com/~benbradley
 
On Wed, 28 Apr 2004 20:17:12 -0400, Ben Bradley wrote:

In sci.electronics.design,comp.arch.embedded, Bob Stephens
stephensyomamadigital@earthlink.net> wrote:


The only Cygnal part I have used is the '060 - I can't speak to the rest.
The data sheet specs as regards power consumption, and internal Vref
performance are extremely misleading at best. We are using it in a battery
powered device, and with the analog peripherals running it is an extreme
power hog. Vdd typical with CPU active is stated as 18 mA, "Power supply
^^^^^^^
Current (each ADC)is given as 4.0 mA typical.
^^^^^^^

SOAPBOX,MODE="ON"

ahem

DO NOT DESIGN WITH "TYPICAL" VALUES.

Every chip can be at the stated minimum or maximum (whichver is
worst case) and still be within spec. If they don't have a max current
or power condumption spec, then that's bad, because it can pull five
amperes and (as long as everything else functions within guaranteed
specs) still be "within spec."
If there is some minumum or maximum spec that the chip isn't
meeting (as long as there's no asterisk where it says "these are just
approximate, we don't guarantee them" or other such weasel words),
then you can call the manufacturer and say they have defective parts,
and reasonably ask that they be replaced.
OTOH, every data sheet says specs 'may change at any time' so they
might just change the specs when you complain, but if any
manudfacturer did things like that there would be a LOT of people
complaining about it on Usenet and elsewhere,

Bob Pease has given this lecture at least once, I forget if it was
in his ED column or 'live' as part of is National tour ... ISTR he
suggested running white-out down the 'typical' column of data sheets -
regardless, that's a good idea.


Well, I'm measuring around
85mA total for Vdd and AVdd with one converter running. Also "The
independent, temperature stable 1.25 V bandgap voltage reference generator,
with an output buffer amplifier which multiplies the bandgap reference by
2" comes in at about 2.4401 volts except when it's warm or cold or ... and
varies from device to device. I've had to add an external precision Vref to
get any kind of stability out of the converters - not a big deal if planned
up front but a thumping PITA to tack on to a densely packed board after the
fact.

-----
http://mindspring.com/~benbradley
Click to expand...
What you say is of course true. The problem in this case is that the
"datasheet" is over 300 pages long and contradicts itself all over the
place and as regards maximum and minimum specs the most common value for
this part is "TBD"...

Bob

<SOAPBOX_MODE &= 0x00;> //you forgot to turn it off
--
"Just machines that make big decisions
programmed by fellas with compassion and vision."
-D. Fagen
(remove yomama)
 
"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> a écrit dans le message
news: s7e090hmiiu7kj8aup5debfmhoc5o6u27f@4ax.com...
On Thu, 29 Apr 2004 10:56:05 +1200, the renowned Jim Granville
no.spam@designtools.co.nz> wrote:

Vref stability is a matter for the fine print. ALL Vrefs will differ
from unit to unit, and also vary over temperature.
The key point is, by how much ?

[They quote 2.44V, or 2.43V Typical as Vref, so 'about 2.4401' does not
sound too terrible ? ]

Their spec also says typ 15ppm/'C tempco.
That's not the very best, but Maxim sell plenty of Vrefs worse than
that. Remember this is an ON-CHIP, Vref.

An on-chip Vref has the disadvantage that it is at the die temperature
for the micro. No big deal if the micro is running at a couple of mA
and not switching much, but if it is running hot you can get
objectionable (perhaps on cosmetic grounds) drift during warm-up.
Click to expand...

If you have a power hungry uC and plenty of unused CPU time then you have
die temperature control for (almost) free.


Fred.
 
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