Voltage to PWM chip (similar to class D)?

Joerg · May 30, 2014

Folks,

Does anyone know an IC that can turn a control voltage into PWM and can
handle PWM frequencies in the 50-1000kHz range? Similar to a class D
driver but has to go down to DC. The changes in control would be
restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with
555-style timers or switcher chips. I am looking for better 1% and
ideally a lot better, including nonlinearity, drift, warts and all. A uC
is not suitable either because it should be simple and I need very fine
control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

--
Regards, Joerg

http://www.analogconsultants.com/

Lasse Langwadt Christense · May 30, 2014

Den torsdag den 29. maj 2014 23.20.26 UTC+2 skrev Joerg:

Folks,

Does anyone know an IC that can turn a control voltage into PWM and can

handle PWM frequencies in the 50-1000kHz range? Similar to a class D

driver but has to go down to DC. The changes in control would be

restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with

555-style timers or switcher chips. I am looking for better 1% and

ideally a lot better, including nonlinearity, drift, warts and all. A uC

is not suitable either because it should be simple and I need very fine

control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

does it have to be pwm?

not hysteretic, deltasigma or UcD ?

http://www.hypex.nl/technology/ucd.html

-Lasse

May 30, 2014

>"PWM frequencies in the 50-1000kHz range?..."

Is it fifty or a thousand ? It makes a difference.

Lasse Langwadt Christense · May 30, 2014

Den torsdag den 29. maj 2014 23.53.48 UTC+2 skrev John Larkin:

On Thu, 29 May 2014 14:20:26 -0700, Joerg <invalid@invalid.invalid

wrote:

Folks,

Does anyone know an IC that can turn a control voltage into PWM and can

handle PWM frequencies in the 50-1000kHz range? Similar to a class D

driver but has to go down to DC. The changes in control would be

restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with

555-style timers or switcher chips. I am looking for better 1% and

ideally a lot better, including nonlinearity, drift, warts and all. A uC

is not suitable either because it should be simple and I need very fine

control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

How about a sawtooth or triangle waveform and a comparator. Close a

feedback loop around that, with a PWM to DC converter; the PWM-DC part

can be made very linear.

put loop around integrator,comparator and flipflop and you have deltasigma

cut down to the bone,

Version 4
SHEET 1 880 680
WIRE 496 -64 64 -64
WIRE -32 112 -96 112
WIRE 64 112 64 16
WIRE 64 112 48 112
WIRE 80 112 64 112
WIRE 192 112 80 112
WIRE -96 128 -96 112
WIRE 192 128 192 112
WIRE 272 128 192 128
WIRE 80 144 80 112
WIRE 272 176 208 176
WIRE 496 176 496 -64
WIRE 496 176 448 176
WIRE 608 176 576 176
WIRE 80 240 80 208
WIRE 208 256 208 176
WIRE -96 384 -96 208
WIRE 208 400 208 336
FLAG -96 384 0
FLAG 272 224 0
FLAG 208 400 0
FLAG 608 240 0
FLAG 80 240 0
SYMBOL voltage -96 112 R0
WINDOW 3 -226 54 Left 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value SINE(.5 .4 1000)
SYMBOL Digital\\dflop 352 80 R0
SYMATTR InstName A1
SYMBOL res 64 96 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL res 48 -80 R0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL cap 96 208 R180
WINDOW 0 24 56 Left 2
WINDOW 3 24 8 Left 2
SYMATTR InstName C1
SYMATTR Value 10n
SYMBOL voltage 208 240 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V3
SYMATTR Value PULSE(0 1 0 1n 1n 500n 1000n)
SYMBOL res 592 160 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 1k
SYMBOL cap 624 240 R180
WINDOW 0 24 56 Left 2
WINDOW 3 24 8 Left 2
SYMATTR InstName C2
SYMATTR Value 10n
TEXT -130 488 Left 2 !.tran 100m

Jim Thompson · May 30, 2014

On Thu, 29 May 2014 14:20:26 -0700, Joerg <invalid@invalid.invalid>
wrote:

Folks,

Does anyone know an IC that can turn a control voltage into PWM and can
handle PWM frequencies in the 50-1000kHz range? Similar to a class D
driver but has to go down to DC. The changes in control would be
restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with
555-style timers or switcher chips. I am looking for better 1% and
ideally a lot better, including nonlinearity, drift, warts and all. A uC
is not suitable either because it should be simple and I need very fine
control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

I can design you a chip >:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice

John Larkin · May 30, 2014

On Thu, 29 May 2014 14:20:26 -0700, Joerg <invalid@invalid.invalid>
wrote:

Folks,

Does anyone know an IC that can turn a control voltage into PWM and can
handle PWM frequencies in the 50-1000kHz range? Similar to a class D
driver but has to go down to DC. The changes in control would be
restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with
555-style timers or switcher chips. I am looking for better 1% and
ideally a lot better, including nonlinearity, drift, warts and all. A uC
is not suitable either because it should be simple and I need very fine
control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

How about a sawtooth or triangle waveform and a comparator. Close a
feedback loop around that, with a PWM to DC converter; the PWM-DC part
can be made very linear.

--

John Larkin Highland Technology, Inc

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

Phil Hobbs · May 30, 2014

On 5/29/2014 5:20 PM, Joerg wrote:

Folks,

Does anyone know an IC that can turn a control voltage into PWM and can
handle PWM frequencies in the 50-1000kHz range? Similar to a class D
driver but has to go down to DC. The changes in control would be
restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with
555-style timers or switcher chips. I am looking for better 1% and
ideally a lot better, including nonlinearity, drift, warts and all. A uC
is not suitable either because it should be simple and I need very fine
control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

How about a CMOS 555 with a current source to charge the capacitor?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

Joerg · May 30, 2014

Lasse Langwadt Christensen wrote:

Den torsdag den 29. maj 2014 23.20.26 UTC+2 skrev Joerg:
Folks,

Does anyone know an IC that can turn a control voltage into PWM and can

handle PWM frequencies in the 50-1000kHz range? Similar to a class D

driver but has to go down to DC. The changes in control would be

restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with

555-style timers or switcher chips. I am looking for better 1% and

ideally a lot better, including nonlinearity, drift, warts and all. A uC

is not suitable either because it should be simple and I need very fine

control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

does it have to be pwm?

not hysteretic, deltasigma or UcD ?

http://www.hypex.nl/technology/ucd.html

This one has to be PWM but we can possible delinearize upfront (possibly
....). Better would be a clean 1:1 PWM.

--
Regards, Joerg

http://www.analogconsultants.com/

Joerg · May 30, 2014

jurb6006@gmail.com wrote:

"PWM frequencies in the 50-1000kHz range?..."

Is it fifty or a thousand ? It makes a difference.

Sorry, 50kHz to 1000kHz.

--
Regards, Joerg

http://www.analogconsultants.com/

Joerg · May 30, 2014

John Larkin wrote:

On Thu, 29 May 2014 14:20:26 -0700, Joerg <invalid@invalid.invalid
wrote:

Folks,

Does anyone know an IC that can turn a control voltage into PWM and can
handle PWM frequencies in the 50-1000kHz range? Similar to a class D
driver but has to go down to DC. The changes in control would be
restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with
555-style timers or switcher chips. I am looking for better 1% and
ideally a lot better, including nonlinearity, drift, warts and all. A uC
is not suitable either because it should be simple and I need very fine
control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

How about a sawtooth or triangle waveform and a comparator. Close a
feedback loop around that, with a PWM to DC converter; the PWM-DC part
can be made very linear.

That's what I wanted to avoid for real estate reasons. But if I hafta
I'll do it.

--
Regards, Joerg

http://www.analogconsultants.com/

Joerg · May 30, 2014

Phil Hobbs wrote:

On 5/29/2014 5:20 PM, Joerg wrote:
Folks,

Does anyone know an IC that can turn a control voltage into PWM and can
handle PWM frequencies in the 50-1000kHz range? Similar to a class D
driver but has to go down to DC. The changes in control would be
restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with
555-style timers or switcher chips. I am looking for better 1% and
ideally a lot better, including nonlinearity, drift, warts and all. A uC
is not suitable either because it should be simple and I need very fine
control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

How about a CMOS 555 with a current source to charge the capacitor?

That could be done but would gradually lead me to the circuit complexity
(size) of a comparator solution. Because I'd have to control the current
source over a wide range and very precisely.

I was hoping I'd not be the only one needing a precise voltage-to-PWM
function.

--
Regards, Joerg

http://www.analogconsultants.com/

John Larkin · May 30, 2014

On Thu, 29 May 2014 18:07:45 -0700, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Thu, 29 May 2014 14:20:26 -0700, Joerg <invalid@invalid.invalid
wrote:

Folks,

Does anyone know an IC that can turn a control voltage into PWM and can
handle PWM frequencies in the 50-1000kHz range? Similar to a class D
driver but has to go down to DC. The changes in control would be
restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with
555-style timers or switcher chips. I am looking for better 1% and
ideally a lot better, including nonlinearity, drift, warts and all. A uC
is not suitable either because it should be simple and I need very fine
control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

How about a sawtooth or triangle waveform and a comparator. Close a
feedback loop around that, with a PWM to DC converter; the PWM-DC part
can be made very linear.

That's what I wanted to avoid for real estate reasons. But if I hafta
I'll do it.

If you want 0.1% accuracy, you might be able to do it open-loop, with a very
linear ramp, but it will be hard at that frequency. If you only want 0.1%
resolution ("granularity"?) it's not so bad.

Can you use delta-sigma? There are some integrated d-s modulators around.

--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation

Lasse Langwadt Christense · May 30, 2014

Den fredag den 30. maj 2014 16.15.46 UTC+2 skrev Joerg:

John Larkin wrote:

On Thu, 29 May 2014 18:07:45 -0700, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:

On Thu, 29 May 2014 14:20:26 -0700, Joerg <invalid@invalid.invalid

wrote:

Folks,

Does anyone know an IC that can turn a control voltage into PWM and can

handle PWM frequencies in the 50-1000kHz range? Similar to a class D

driver but has to go down to DC. The changes in control would be

restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with

555-style timers or switcher chips. I am looking for better 1% and

ideally a lot better, including nonlinearity, drift, warts and all. A uC

is not suitable either because it should be simple and I need very fine

control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

How about a sawtooth or triangle waveform and a comparator. Close a

feedback loop around that, with a PWM to DC converter; the PWM-DC part

can be made very linear.

That's what I wanted to avoid for real estate reasons. But if I hafta

I'll do it.

If you want 0.1% accuracy, you might be able to do it open-loop, with a very

linear ramp, but it will be hard at that frequency. If you only want 0.1%

resolution ("granularity"?) it's not so bad.

Can you use delta-sigma? There are some integrated d-s modulators around.

I could but then I'd have to build a one-shot that stretches the pulses

into a very precise length and that's almost the same kind of challenge

as building my own PWM generator (needs too much space).

why would you need a one-shot? the output is clocked

something like the AD7401, if you want to be sure a flipflop on the output

-Lasse

Lasse Langwadt Christense · May 30, 2014

Den fredag den 30. maj 2014 17.32.27 UTC+2 skrev Reinhardt Behm:

Tim Wescott wrote:

On Thu, 29 May 2014 14:20:26 -0700, Joerg wrote:

Folks,

Does anyone know an IC that can turn a control voltage into PWM and can

handle PWM frequencies in the 50-1000kHz range? Similar to a class D

driver but has to go down to DC. The changes in control would be

restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with

555-style timers or switcher chips. I am looking for better 1% and

ideally a lot better, including nonlinearity, drift, warts and all. A uC

is not suitable either because it should be simple and I need very fine

control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

Hey! Microprocessors are simple! You just need to learn some valuable

skills, that's all.

http://www.c-for-dummies.com/

But generating a PWM at 1MHz with a resolution of 0.1% mean you need a base

frequency for your counter of 1GHz. I don't know any CPU that could do that.

he did say the input was limited to 15KHz, so 2*15K*1000 >= 30MHz

plenty of cpus that can do that

-Lasse

whit3rd · May 30, 2014

On Thursday, May 29, 2014 6:07:45 PM UTC-7, Joerg wrote:

John Larkin wrote:

How about a sawtooth or triangle waveform and a comparator. Close a
feedback loop around that, with a PWM to DC converter; the PWM-DC part
can be made very linear.

That's what I wanted to avoid for real estate reasons.

It's only a dual comparator and a transistor! The first comparator is set
up as a Schmitt trigger with thresholds at +Vs and -Vs; its output drives
a resistor to the base, capacitor from collector to base, emitter to V-.
That makes a triangle wave. The second comparator takes signal in
on one input, and triangle wave on the other, and you're done.

May 30, 2014

On Thursday, May 29, 2014 9:10:45 PM UTC-4, Joerg wrote:

Phil Hobbs wrote:
On 5/29/2014 5:20 PM, Joerg wrote:
Folks,

Does anyone know an IC that can turn a control voltage into PWM and can
handle PWM frequencies in the 50-1000kHz range? Similar to a class D
driver but has to go down to DC. The changes in control would be
restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with
555-style timers or switcher chips. I am looking for better 1% and
ideally a lot better, including nonlinearity, drift, warts and all. A uC
is not suitable either because it should be simple and I need very fine
control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

How about a CMOS 555 with a current source to charge the capacitor?

That could be done but would gradually lead me to the circuit complexity
(size) of a comparator solution. Because I'd have to control the current
source over a wide range and very precisely.

The current source would be fixed, not variable "over a wide range."
That's trivial.

555 comparator drift might be a problem, but there might be precision
versions without it.

The 555 is cheap and small enough that it's almost worth using just
for the internal logic...

Cheers,
James Arthur

May 30, 2014

On Friday, May 30, 2014 12:45:25 PM UTC-4, Joerg wrote:

Digital is ok but 1000:1 granularity at a MHz or at least half a MHz
would require a fat processor with really good timer resources.

Okay, that narrows the field--too fast for a 555!

It's going to be hard to get good linearity from any consumer
part, and it's hard to imagine who'd need it other than class-D
audio.

Cheers,
James Arthur

Lasse Langwadt Christense · May 30, 2014

Den fredag den 30. maj 2014 18.34.37 UTC+2 skrev Joerg:

Lasse Langwadt Christensen wrote:

Den fredag den 30. maj 2014 16.15.46 UTC+2 skrev Joerg:

John Larkin wrote:

On Thu, 29 May 2014 18:07:45 -0700, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:

On Thu, 29 May 2014 14:20:26 -0700, Joerg <invalid@invalid.invalid

wrote:

Folks,

Does anyone know an IC that can turn a control voltage into PWM and can

handle PWM frequencies in the 50-1000kHz range? Similar to a class D

driver but has to go down to DC. The changes in control would be

restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with

555-style timers or switcher chips. I am looking for better 1% and

ideally a lot better, including nonlinearity, drift, warts and all. A uC

is not suitable either because it should be simple and I need very fine

control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.

How about a sawtooth or triangle waveform and a comparator. Close a

feedback loop around that, with a PWM to DC converter; the PWM-DC part

can be made very linear.

That's what I wanted to avoid for real estate reasons. But if I hafta

I'll do it.

If you want 0.1% accuracy, you might be able to do it open-loop, with a very

linear ramp, but it will be hard at that frequency. If you only want 0.1%

resolution ("granularity"?) it's not so bad.

Can you use delta-sigma? There are some integrated d-s modulators around.

I could but then I'd have to build a one-shot that stretches the pulses

into a very precise length and that's almost the same kind of challenge

as building my own PWM generator (needs too much space).

why would you need a one-shot? the output is clocked

something like the AD7401, if you want to be sure a flipflop on the output

It's possible but when assuming a master clock of 20MHz going in and I'd

want, say, a 1k granularity that would result in an effective PWM of

only 20kHz. Unless I am understanding something wrong in the datasheet.

with DS is hard to talk about pwm frequency, it has noise shaping so the
switching noise gets pushed to higher frequencies. i.e if you are exactly midrange the "pwm frequency" would be 10MHz

with a brick wall reconstructions filter you would normally gain 3dB every
time you double the sampling frequency, with a second order deltasigma you
gain ~15dB, first order ~9dB

http://www.analog.com/static/imported-files/data_sheets/AD7401.pdf

What I'd essentially need is a class D audio modulator but without the

DC cut-off. Unfortunately that's as rare as it is on audio CODECs where

only a few such as the AD1939 can go down to DC without onerous offset

issues or huge drift.

if you can live with the higher switching frequency I think deltasigma
would do that

-Lasse

Joerg · May 30, 2014

John Larkin wrote:

On Thu, 29 May 2014 18:07:45 -0700, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Thu, 29 May 2014 14:20:26 -0700, Joerg <invalid@invalid.invalid
wrote:

Folks,

Does anyone know an IC that can turn a control voltage into PWM and can
handle PWM frequencies in the 50-1000kHz range? Similar to a class D
driver but has to go down to DC. The changes in control would be
restricted to the audio spectrum below 15kHz.

The LTC6992 does this nicely but isn't precise enough. Same with
555-style timers or switcher chips. I am looking for better 1% and
ideally a lot better, including nonlinearity, drift, warts and all. A uC
is not suitable either because it should be simple and I need very fine
control granularity, down to around 0.1%.

Can't use short-lived consumer chips for radios and TV sets and such.
How about a sawtooth or triangle waveform and a comparator. Close a
feedback loop around that, with a PWM to DC converter; the PWM-DC part
can be made very linear.

That's what I wanted to avoid for real estate reasons. But if I hafta
I'll do it.

If you want 0.1% accuracy, you might be able to do it open-loop, with a very
linear ramp, but it will be hard at that frequency. If you only want 0.1%
resolution ("granularity"?) it's not so bad.

Can you use delta-sigma? There are some integrated d-s modulators around.

I could but then I'd have to build a one-shot that stretches the pulses
into a very precise length and that's almost the same kind of challenge
as building my own PWM generator (needs too much space).

--
Regards, Joerg

http://www.analogconsultants.com/

George Herold · May 30, 2014

On Friday, May 30, 2014 11:32:27 AM UTC-4, Reinhardt Behm wrote:

Tim Wescott wrote:
snip

Hey! Microprocessors are simple! You just need to learn some valuable
skills, that's all.

http://www.c-for-dummies.com/

But generating a PWM at 1MHz with a resolution of 0.1% mean you need a base
frequency for your counter of 1GHz. I don't know any CPU that could do that.

Only if you needed it "right away", if you could average 100 cycles,
then you could do it with 10MHz.

George H.

--
Reinhardt Behm

Voltage to PWM chip (similar to class D)?

Joerg

Guest

Lasse Langwadt Christense

Guest

Guest

Lasse Langwadt Christense

Guest

Jim Thompson

Guest

John Larkin

Guest

Phil Hobbs

Guest

Joerg

Guest

Joerg

Guest

Joerg

Guest

Joerg

Guest

John Larkin

Guest

Lasse Langwadt Christense

Guest

Lasse Langwadt Christense

Guest

whit3rd

Guest

Guest

Guest

Lasse Langwadt Christense

Guest

Joerg

Guest

George Herold

Guest

Log in

Welcome to EDABoard.com

Sponsor