4046 PLL question

R

Robert Latest

Guest
A short question on the "Type 2" phase detector: On page 648 of AoE it
says that this detector has a gain of VDD/(2*pi) which I find plausible
because the lowpass output goes from 0V to VDD as the phase difference
of the input signal goes from -pi to +pi.

However, both the ON semi and the Philips datasheets say that
Kp=VDD/(4*pi). I double-checked and made sure that all three sources
talk about the 4046's output pin # 13.

Why the discrepancy?

robert
 
"Robert Latest" <boblatest@yahoo.com> wrote in message
news:3l6if0F10v96rU1@individual.net...
A short question on the "Type 2" phase detector: On page 648 of AoE it
says that this detector has a gain of VDD/(2*pi) which I find plausible
because the lowpass output goes from 0V to VDD as the phase difference
of the input signal goes from -pi to +pi.

However, both the ON semi and the Philips datasheets say that
Kp=VDD/(4*pi). I double-checked and made sure that all three sources
talk about the 4046's output pin # 13.

Why the discrepancy?

robert
Click to expand...
Yes.... I once wondered about something like that but couldn't be arsed.

However I do believe there is a discrepency somewhere and someone else
should sort their bum out.

DNA
 
A short question on the "Type 2" phase detector: On page 648 of AoE it
says that this detector has a gain of VDD/(2*pi) which I find plausible
because the lowpass output goes from 0V to VDD as the phase difference
of the input signal goes from -pi to +pi.
Click to expand...
AoE is obviously referring the 4046 PC3 phase comparator, and the
datasheets are referring to the PC2 phase comparator. The PC3 is a
toggle FF, and the PC2 is a dual FF phase/frequency comparator.

However, both the ON semi and the Philips datasheets say that
Kp=VDD/(4*pi). I double-checked and made sure that all three sources
talk about the 4046's output pin # 13.

Why the discrepancy?
Click to expand...
Your lack of comprehension. These datasheets are full of
self-explanatory graphics, equations , and write-ups.
 
Genome wrote:

Yes.... I once wondered about something like that but couldn't be arsed.

However I do believe there is a discrepency somewhere and someone else
should sort their bum out.
Click to expand...

Just a bunch of nitpicking nonsense...
 
On Mon, 01 Aug 2005 12:58:59 GMT,
Fred Bloggs <nospam@nospam.com> wrote
in Msg. <42EE1C90.1060201@nospam.com>

AoE is obviously referring the 4046 PC3 phase comparator, and the
datasheets are referring to the PC2 phase comparator. The PC3 is a
toggle FF, and the PC2 is a dual FF phase/frequency comparator.
Click to expand...
No. They refer to the same pin number (13), and Fig. 9 in the Philips
data sheet corresponds to Fig. 9.69 in AoE. They clearly both refer to
what Philips calls PC2. Fig. 11 (Philips) shows the output of PC3, which
is not what AoE talks about.

According to Philips, PC2's gain is Vcc/4pi, but AoE says it's Vcc/2pi.

Your lack of comprehension.
Click to expand...
I'm trying to rectify that.

robert
 
"Robert Latest" <boblatest@yahoo.com> wrote in message
news:3l6if0F10v96rU1@individual.net...
A short question on the "Type 2" phase detector: On page 648 of AoE it
says that this detector has a gain of VDD/(2*pi) which I find plausible
because the lowpass output goes from 0V to VDD as the phase difference
of the input signal goes from -pi to +pi.

However, both the ON semi and the Philips datasheets say that
Kp=VDD/(4*pi). I double-checked and made sure that all three sources
talk about the 4046's output pin # 13.

Why the discrepancy?

robert


You don't say what family 4046 you are using. The HC/HCT parts are quite
Click to expand...
different, depending on manufacturer. Just look at the max frequency to get
a clew. I think the Moto (ON), and the Philips were the most alike.

Tam

Tam
 
On 1 Aug 2005 16:52:42 GMT, Robert Latest <boblatest@yahoo.com> wrote:

On Mon, 01 Aug 2005 12:58:59 GMT,
Fred Bloggs <nospam@nospam.com> wrote
in Msg. <42EE1C90.1060201@nospam.com

AoE is obviously referring the 4046 PC3 phase comparator, and the
datasheets are referring to the PC2 phase comparator. The PC3 is a
toggle FF, and the PC2 is a dual FF phase/frequency comparator.

No. They refer to the same pin number (13), and Fig. 9 in the Philips
data sheet corresponds to Fig. 9.69 in AoE. They clearly both refer to
what Philips calls PC2. Fig. 11 (Philips) shows the output of PC3, which
is not what AoE talks about.

According to Philips, PC2's gain is Vcc/4pi, but AoE says it's Vcc/2pi.

Your lack of comprehension.

I'm trying to rectify that.

robert
Click to expand...
The output of an edge-matching phase detector is Vcc at +2*pi

The output of an edge-matching phase detector is 0 (zero) at -2*pi

So Vcc/(4*pi) is correct, and AoE is incorrect ;-)

(I am co-inventor of the first edge-matching device, MC4046)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
VDD/(2*pi) vs VdDD/(4*pi)
Why the discrepancy?
Click to expand...
I think this is addressed in Appendix B of TI's app note on the 4046,
SCHA003B is the document name.

They say that before lock, when the correction is only in one direction
to slew the frequency, that the Vcc/(2pi) is the gain. But after lock,
when the corrections are small pulses and not always in the same
direction, and the correction is made from roughly (Vcc/2), then
Vcc/(4pi) is more appropriate.

Tim.
 
On Mon, 01 Aug 2005 10:29:17 -0700, Jim Thompson
<thegreatone@example.com> wrote:

[snip]
(I am co-inventor of the first edge-matching device, MC4046)

...Jim Thompson
Click to expand...
Wrong number, make that MC4044.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
On 1 Aug 2005 11:14:02 -0700, "Tim Shoppa" <shoppa@trailing-edge.com>
wrote:

VDD/(2*pi) vs VdDD/(4*pi)
Why the discrepancy?

I think this is addressed in Appendix B of TI's app note on the 4046,
SCHA003B is the document name.

They say that before lock, when the correction is only in one direction
to slew the frequency, that the Vcc/(2pi) is the gain. But after lock,
when the corrections are small pulses and not always in the same
direction, and the correction is made from roughly (Vcc/2), then
Vcc/(4pi) is more appropriate.

Tim.
Click to expand...
Sounds like something written by an apps engineer without a clue.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
On 2005-08-01, Jim Thompson <thegreatone@example.com> wrote:

The output of an edge-matching phase detector is Vcc at +2*pi

The output of an edge-matching phase detector is 0 (zero) at -2*pi

So Vcc/(4*pi) is correct, and AoE is incorrect ;-)
Click to expand...
Yup. I had found out by now, too. It's not really that difficult;
I was just confused.

robert
 
Robert Latest wrote:

A short question on the "Type 2" phase detector: On page 648 of AoE it
says that this detector has a gain of VDD/(2*pi) which I find plausible
because the lowpass output goes from 0V to VDD as the phase difference
of the input signal goes from -pi to +pi.

However, both the ON semi and the Philips datasheets say that
Kp=VDD/(4*pi). I double-checked and made sure that all three sources
talk about the 4046's output pin # 13.

Why the discrepancy?

robert


Keep in mind that pin 13 (whatever your particular data sheet calls that
Click to expand...
phase detector) is high impedance most of the time in lock, and only low
impedance while the thing is detecting phase mismatch. The thing is
designed to connect like this:

|
|
to VCO|--------------.
| ___ |
pin 13|------|___|---o
| |
| |
| ---
---
|
|
===
GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

(note that what I'm saying is still valid for more complex loop
filters). The charge pulse that gets injected into the capacitor is
dependent on the voltage across the capacitor as well as the phase error
-- so if the cap is sitting at 1/5 VCC then it will have a 4:1
difference in the response to a phase error in one direction as it will
in the other. You need to take this into account when you design your
loop filter, usually by including lots of extra gain margin.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
On Tue, 02 Aug 2005 08:55:02 -0700, Tim Wescott <tim@seemywebsite.com>
wrote:

Robert Latest wrote:

A short question on the "Type 2" phase detector: On page 648 of AoE it
says that this detector has a gain of VDD/(2*pi) which I find plausible
because the lowpass output goes from 0V to VDD as the phase difference
of the input signal goes from -pi to +pi.

However, both the ON semi and the Philips datasheets say that
Kp=VDD/(4*pi). I double-checked and made sure that all three sources
talk about the 4046's output pin # 13.

Why the discrepancy?

robert


Keep in mind that pin 13 (whatever your particular data sheet calls that
phase detector) is high impedance most of the time in lock, and only low
impedance while the thing is detecting phase mismatch. The thing is
designed to connect like this:

|
|
to VCO|--------------.
| ___ |
pin 13|------|___|---o
| |
| |
| ---
---
|
|
===
GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

(note that what I'm saying is still valid for more complex loop
filters). The charge pulse that gets injected into the capacitor is
dependent on the voltage across the capacitor as well as the phase error
-- so if the cap is sitting at 1/5 VCC then it will have a 4:1
difference in the response to a phase error in one direction as it will
in the other. You need to take this into account when you design your
loop filter, usually by including lots of extra gain margin.
Click to expand...
The best embodiment is that the phase detector output is a current
source/sink.

Or work the 4046 "switches" thru a resistor into a virtual ground.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Jim Thompson wrote:

On Tue, 02 Aug 2005 08:55:02 -0700, Tim Wescott <tim@seemywebsite.com
wrote:


Robert Latest wrote:


A short question on the "Type 2" phase detector: On page 648 of AoE it
says that this detector has a gain of VDD/(2*pi) which I find plausible
because the lowpass output goes from 0V to VDD as the phase difference
of the input signal goes from -pi to +pi.

However, both the ON semi and the Philips datasheets say that
Kp=VDD/(4*pi). I double-checked and made sure that all three sources
talk about the 4046's output pin # 13.

Why the discrepancy?

robert



Keep in mind that pin 13 (whatever your particular data sheet calls that
phase detector) is high impedance most of the time in lock, and only low
impedance while the thing is detecting phase mismatch. The thing is
designed to connect like this:

|
|
to VCO|--------------.
| ___ |
pin 13|------|___|---o
| |
| |
| ---
---
|
|
===
GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

(note that what I'm saying is still valid for more complex loop
filters). The charge pulse that gets injected into the capacitor is
dependent on the voltage across the capacitor as well as the phase error
-- so if the cap is sitting at 1/5 VCC then it will have a 4:1
difference in the response to a phase error in one direction as it will
in the other. You need to take this into account when you design your
loop filter, usually by including lots of extra gain margin.


The best embodiment is that the phase detector output is a current
source/sink.

Or work the 4046 "switches" thru a resistor into a virtual ground.

...Jim Thompson
Click to expand...
The better PLL chips have some magic circuitry* to make them look like
controlled-current sources when they're active, rather than hard shorts
to ground or VCC. To get the same effect with a 4046 you'd have to work
into an op-amp with a virtual ground, and you'd have to take the
op-amp's noise into account in your circuit design.

* that's what you do, Jim -- you put the magic into the little black
bugs; I just use them.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
Andy asks Jim :

Were you working with Jon deLaune at the time ?

Andy
 
On Tue, 02 Aug 2005 10:21:52 -0700, Tim Wescott <tim@seemywebsite.com>
wrote:

Jim Thompson wrote:

On Tue, 02 Aug 2005 08:55:02 -0700, Tim Wescott <tim@seemywebsite.com
wrote:


Robert Latest wrote:


A short question on the "Type 2" phase detector: On page 648 of AoE it
says that this detector has a gain of VDD/(2*pi) which I find plausible
because the lowpass output goes from 0V to VDD as the phase difference
of the input signal goes from -pi to +pi.

However, both the ON semi and the Philips datasheets say that
Kp=VDD/(4*pi). I double-checked and made sure that all three sources
talk about the 4046's output pin # 13.

Why the discrepancy?

robert



Keep in mind that pin 13 (whatever your particular data sheet calls that
phase detector) is high impedance most of the time in lock, and only low
impedance while the thing is detecting phase mismatch. The thing is
designed to connect like this:

|
|
to VCO|--------------.
| ___ |
pin 13|------|___|---o
| |
| |
| ---
---
|
|
===
GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

(note that what I'm saying is still valid for more complex loop
filters). The charge pulse that gets injected into the capacitor is
dependent on the voltage across the capacitor as well as the phase error
-- so if the cap is sitting at 1/5 VCC then it will have a 4:1
difference in the response to a phase error in one direction as it will
in the other. You need to take this into account when you design your
loop filter, usually by including lots of extra gain margin.


The best embodiment is that the phase detector output is a current
source/sink.

Or work the 4046 "switches" thru a resistor into a virtual ground.

...Jim Thompson

The better PLL chips have some magic circuitry* to make them look like
controlled-current sources when they're active, rather than hard shorts
to ground or VCC. To get the same effect with a 4046 you'd have to work
into an op-amp with a virtual ground, and you'd have to take the
op-amp's noise into account in your circuit design.

* that's what you do, Jim -- you put the magic into the little black
bugs; I just use them.
Click to expand...
I can't remember when I didn't use current source/sink for PD outputs.

Yes I can, the original MC4044 used R's into a fed back Darlington.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
On 2 Aug 2005 10:29:16 -0700, "Andy" <andysharpe@juno.com> wrote:

Andy asks Jim :

Were you working with Jon deLaune at the time ?

Andy
Click to expand...
I remember the name, but he was in another group... maybe
applications?

I was in analog research/design at Motorola.

Do you know Jon from somewhere?

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Jim Thompson wrote:
On Tue, 02 Aug 2005 10:21:52 -0700, Tim Wescott <tim@seemywebsite.com
wrote:


Jim Thompson wrote:


On Tue, 02 Aug 2005 08:55:02 -0700, Tim Wescott <tim@seemywebsite.com
wrote:



Robert Latest wrote:



A short question on the "Type 2" phase detector: On page 648 of AoE it
says that this detector has a gain of VDD/(2*pi) which I find plausible
because the lowpass output goes from 0V to VDD as the phase difference
of the input signal goes from -pi to +pi.

However, both the ON semi and the Philips datasheets say that
Kp=VDD/(4*pi). I double-checked and made sure that all three sources
talk about the 4046's output pin # 13.

Why the discrepancy?

robert



Keep in mind that pin 13 (whatever your particular data sheet calls that
phase detector) is high impedance most of the time in lock, and only low
impedance while the thing is detecting phase mismatch. The thing is
designed to connect like this:

|
|
to VCO|--------------.
| ___ |
pin 13|------|___|---o
| |
| |
| ---
---
|
|
===
GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

(note that what I'm saying is still valid for more complex loop
filters). The charge pulse that gets injected into the capacitor is
dependent on the voltage across the capacitor as well as the phase error
-- so if the cap is sitting at 1/5 VCC then it will have a 4:1
difference in the response to a phase error in one direction as it will
in the other. You need to take this into account when you design your
loop filter, usually by including lots of extra gain margin.


The best embodiment is that the phase detector output is a current
source/sink.

Or work the 4046 "switches" thru a resistor into a virtual ground.

...Jim Thompson

The better PLL chips have some magic circuitry* to make them look like
controlled-current sources when they're active, rather than hard shorts
to ground or VCC. To get the same effect with a 4046 you'd have to work
into an op-amp with a virtual ground, and you'd have to take the
op-amp's noise into account in your circuit design.

* that's what you do, Jim -- you put the magic into the little black
bugs; I just use them.


I can't remember when I didn't use current source/sink for PD outputs.

Yes I can, the original MC4044 used R's into a fed back Darlington.

...Jim Thompson
Click to expand...
If there's anything missing from the modern line up of tiny-logic chips
it's a 4046-style phase detector (or better yet one with controlled
current outputs) it the World's Smallest Package. My dream chip would
have six pins: VSS, VDD, in1, in2, phase out and current program (which
could be tied high to emulate the 4046 phase detector). This would all
come in a SOT-23 package or a flip-chip.

At the moment if you want just a phase detector you have to use a 4046
with a disabled oscillator and use up extra space not only for the chip
but (possibly) for the aforementioned virtual-ground op amp integrator.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
Andy writes:

I remember seeing his name on the patent, and I think it was for the
MC4044.
I just went to the uspto.gov site, but they only go back to 1976, so I
can't
verify it just now.....
I definitely saw his name on the Motorola app notes for the 4044 , way
back in
the early 70's . ( Funny, the stuff that sticks in your mind
(grin) )

Whoever did it, the 4044 was a fine piece of work that was a major
breakthrough
in the development of frequency control...
I was designing frequency synthesizers at the time for Bendix
Avionics, then later
for Texas Instruments. I used the 4044 in a dozen products, then I
started building
my own with two D's and a reset gate ( same 4044 circuit using D's
instead of
individual gates --- gave me better control over the dead zone).....
Later I expanded it into a quad of D's which gave slightly better pump
action when the frequencies
were widely separated ( Principles of Three State Phase Detection -
EDN- Sharpe ).

But I have always credited the 4044 development with the same sort
of
genius as the light bulb, sliced bread, and peanut butter with
chocolate......

Before the 4044, we were using slip counters for frequency/phase
comparison
( Fairchild applications note dealing with avionics - John Nichols
)
and they were a pain in the ass to analyze. The 4044, especially
when used
with an op amp, made the analysis very straightforward..... Later
versions in
CMOS (4046) had more pump voltage and lower leakage. I couldn't get
a hold
of the dead zone problem , and leakage, until I started building them
out of
separate high speed flipflops.........

Just reminiscing, and the mention of your involvement with the 4044
yanked my
crank enough to respond....

Andy Sharpe
 
Andy responds to Tim:

I would prefer separate outputs for the phase detector Pump up and
pump down, (which I could tie
together if desired ). And a pin for a lock detector, rudimentary
tho it would
have to be......

I Andy Sharpe, retired, PE,
etc........
 
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