ULN regulator with more current capability than LT3042?
Reviving the conversation about superb voltage regulators, I am looking
for one to run the analog and PLL bits of a high performance frequency
synthesizer chip.
The current drain looks to be about 160-180 mA at 1.8 V, which is
uncomfortably close to the limit for the LT3042 (200 mA). The
manufacturer's evaluation board uses a MAX8869, which appears to be
nowhere in the LT3042's league, but will source 1 A.
Any recommendations for a 1.8 V regulator a little beefier than the
LT3042, but with similar noise performance?
Thanks!
John
Use an LT3045, its the 0.5A version of the LT3042.
Bruce
On 19 March 2018 at 09:13 John Ackermann N8UR jra@febo.com wrote:
Reviving the conversation about superb voltage regulators, I am looking
for one to run the analog and PLL bits of a high performance frequency
synthesizer chip.
The current drain looks to be about 160-180 mA at 1.8 V, which is
uncomfortably close to the limit for the LT3042 (200 mA). The
manufacturer's evaluation board uses a MAX8869, which appears to be
nowhere in the LT3042's league, but will source 1 A.
Any recommendations for a 1.8 V regulator a little beefier than the
LT3042, but with similar noise performance?
Thanks!
John
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----- Original Message -----
From: "John Ackermann N8UR" jra@febo.com
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Sunday, March 18, 2018 4:13 PM
Subject: [time-nuts] ULN regulator with more current capability than LT3042?
Reviving the conversation about superb voltage regulators, I am looking
for one to run the analog and PLL bits of a high performance frequency
synthesizer chip.
The current drain looks to be about 160-180 mA at 1.8 V, which is
uncomfortably close to the limit for the LT3042 (200 mA). The
manufacturer's evaluation board uses a MAX8869, which appears to be
nowhere in the LT3042's league, but will source 1 A.
Any recommendations for a 1.8 V regulator a little beefier than the
LT3042, but with similar noise performance?
Thanks!
John
Run two in parallel for twice the current and less noise?
Regards
Thanks, Bruce!!!
On 03/18/2018 04:19 PM, Bruce Griffiths wrote:
Use an LT3045, its the 0.5A version of the LT3042.
Bruce
On 19 March 2018 at 09:13 John Ackermann N8UR jra@febo.com wrote:
Reviving the conversation about superb voltage regulators, I am looking
for one to run the analog and PLL bits of a high performance frequency
synthesizer chip.
The current drain looks to be about 160-180 mA at 1.8 V, which is
uncomfortably close to the limit for the LT3042 (200 mA). The
manufacturer's evaluation board uses a MAX8869, which appears to be
nowhere in the LT3042's league, but will source 1 A.
Any recommendations for a 1.8 V regulator a little beefier than the
LT3042, but with similar noise performance?
Thanks!
John
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Am 18.03.2018 um 21:13 schrieb John Ackermann N8UR:
Reviving the conversation about superb voltage regulators, I am
looking for one to run the analog and PLL bits of a high performance
frequency synthesizer chip.
The current drain looks to be about 160-180 mA at 1.8 V, which is
uncomfortably close to the limit for the LT3042 (200 mA). The
manufacturer's evaluation board uses a MAX8869, which appears to be
nowhere in the LT3042's league, but will source 1 A.
Any recommendations for a 1.8 V regulator a little beefier than the
LT3042, but with similar noise performance?
Use the LT3042 with an external power transistor, such as D44VH10G:
<
https://www.flickr.com/photos/137684711@N07/29197476530/in/album-72157662535945536/
Performance is about the same as the LT3042 alone. That is exactly the
circuit from the data sheet.
<
https://www.flickr.com/photos/137684711@N07/29452163806/in/album-72157662535945536/
The layout for Altium Designer is available.
The LT3045 is not so much bigger that it makes a real progress. The
currents are valid only
for tiny voltage drops anyway.
regards,
Gerhard
Hi
Getting the heat off of the regulator package may have other benefits ( like improved
stability). A lot depends on just where the heat goes in each case …..
Bob
On Mar 18, 2018, at 4:41 PM, Gerhard Hoffmann dk4xp@arcor.de wrote:
Am 18.03.2018 um 21:13 schrieb John Ackermann N8UR:
Reviving the conversation about superb voltage regulators, I am looking for one to run the analog and PLL bits of a high performance frequency synthesizer chip.
The current drain looks to be about 160-180 mA at 1.8 V, which is uncomfortably close to the limit for the LT3042 (200 mA). The manufacturer's evaluation board uses a MAX8869, which appears to be nowhere in the LT3042's league, but will source 1 A.
Any recommendations for a 1.8 V regulator a little beefier than the LT3042, but with similar noise performance?
Use the LT3042 with an external power transistor, such as D44VH10G:
< https://www.flickr.com/photos/137684711@N07/29197476530/in/album-72157662535945536/ >
Performance is about the same as the LT3042 alone. That is exactly the circuit from the data sheet.
< https://www.flickr.com/photos/137684711@N07/29452163806/in/album-72157662535945536/ >
The layout for Altium Designer is available.
The LT3045 is not so much bigger that it makes a real progress. The currents are valid only
for tiny voltage drops anyway.
regards,
Gerhard
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Tom wrote:
Run two in parallel for twice the current and less noise?
This is actually a better solution than using an LT3045, for two
reasons. First, as Tom noted, by paralleling two devices, the noise is
reduced by sqrt 2 = ~1.4:
"Designed as a precision current reference followed by a high
performance voltage buffer, the LT3042 is easily paralleled to increase
output current, spread heat on the PCB and further reduce noise --
output noise decreases by the square-root of the number of devices in
parallel." [LT Journal of Analog Innovation, v25 n1 Apr 2015].
http://www.linear.com/docs/46398
Second, it reduces the dissipation of each regulator, so they run
cooler. And as LT says, it allows spreading the heat on the board (but
it is not advisable to put them too far apart).
The primary disadvantage is that two 3042s cost about half again more
than one 3045. Also, board space may be a factor in some applications.
So, unless you are extremely tight on board space or the ~1.5x cost
increase is prohibitive, two 3042s in parallel are a better solution
than one 3045 if you are seeking the lowest noise possible.
Best regards,
Charles
Please forgive this naive question, but I am concerned about the idea of
simply running two regulators in parallel. Just like you don't put two
batteries in parallel, how do you ensure accurate load balancing between
the two? I would worry that one of them, with a fractionally higher
voltage, would be driven into saturation, thus ruining any noise
isolation. I must be missing something here?
Peter
On 18 March 2018 at 22:43, Charles Steinmetz csteinmetz@yandex.com wrote:
Tom wrote:
Run two in parallel for twice the current and less noise?
This is actually a better solution than using an LT3045, for two reasons.
First, as Tom noted, by paralleling two devices, the noise is reduced by
sqrt 2 = ~1.4:
"Designed as a precision current reference followed by a high performance
voltage buffer, the LT3042 is easily paralleled to increase output current,
spread heat on the PCB and further reduce noise -- output noise decreases
by the square-root of the number of devices in parallel." [LT Journal of
Analog Innovation, v25 n1 Apr 2015]. http://www.linear.com/docs/46398
Second, it reduces the dissipation of each regulator, so they run cooler.
And as LT says, it allows spreading the heat on the board (but it is not
advisable to put them too far apart).
The primary disadvantage is that two 3042s cost about half again more than
one 3045. Also, board space may be a factor in some applications.
So, unless you are extremely tight on board space or the ~1.5x cost
increase is prohibitive, two 3042s in parallel are a better solution than
one 3045 if you are seeking the lowest noise possible.
Best regards,
Charles
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ailman/listinfo/time-nuts
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Thanks, all. I think I'll end up using the 3042 with pass transistor,
partly for reasons of cost. I have no idea whether paralleling two
3042s would result in lower noise from the device, and there are already
three or four fairly pricey chips on the board.
I appreciate all the info!
John
On 03/18/2018 06:43 PM, Charles Steinmetz wrote:
Tom wrote:
Run two in parallel for twice the current and less noise?
This is actually a better solution than using an LT3045, for two
reasons. First, as Tom noted, by paralleling two devices, the noise is
reduced by sqrt 2 = ~1.4:
"Designed as a precision current reference followed by a high
performance voltage buffer, the LT3042 is easily paralleled to increase
output current, spread heat on the PCB and further reduce noise --
output noise decreases by the square-root of the number of devices in
parallel." [LT Journal of Analog Innovation, v25 n1 Apr 2015].
http://www.linear.com/docs/46398
Second, it reduces the dissipation of each regulator, so they run
cooler. And as LT says, it allows spreading the heat on the board (but
it is not advisable to put them too far apart).
The primary disadvantage is that two 3042s cost about half again more
than one 3045. Also, board space may be a factor in some applications.
So, unless you are extremely tight on board space or the ~1.5x cost
increase is prohibitive, two 3042s in parallel are a better solution
than one 3045 if you are seeking the lowest noise possible.
Best regards,
Charles
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I have a quad LT3042 board somewhere.
I should get around to measuring its output noise.
Bruce
On 20 March 2018 at 03:11 John Ackermann N8UR jra@febo.com wrote:
Thanks, all. I think I'll end up using the 3042 with pass transistor,
partly for reasons of cost. I have no idea whether paralleling two
3042s would result in lower noise from the device, and there are already
three or four fairly pricey chips on the board.
I appreciate all the info!
John
On 03/18/2018 06:43 PM, Charles Steinmetz wrote:
Tom wrote:
Run two in parallel for twice the current and less noise?
This is actually a better solution than using an LT3045, for two
reasons. First, as Tom noted, by paralleling two devices, the noise is
reduced by sqrt 2 = ~1.4:
"Designed as a precision current reference followed by a high
performance voltage buffer, the LT3042 is easily paralleled to increase
output current, spread heat on the PCB and further reduce noise --
output noise decreases by the square-root of the number of devices in
parallel." [LT Journal of Analog Innovation, v25 n1 Apr 2015].
http://www.linear.com/docs/46398
Second, it reduces the dissipation of each regulator, so they run
cooler. And as LT says, it allows spreading the heat on the board (but
it is not advisable to put them too far apart).
The primary disadvantage is that two 3042s cost about half again more
than one 3045. Also, board space may be a factor in some applications.
So, unless you are extremely tight on board space or the ~1.5x cost
increase is prohibitive, two 3042s in parallel are a better solution
than one 3045 if you are seeking the lowest noise possible.
Best regards,
Charles
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