Help me with a high accuray VCO design

[opamp741]

vco high accuracy

Hello,
Plz suggest me the architecture of VCO with following specs.

Freq range : 400-600KHz
Accuracy : 2% (i think this is too tough to meet but still the customer wants such accuracy)
Limit : only one high accuracy external component (R/C) is allowed
Technology : CMOS 1.2V

Thanx
Opamp741

 

[FANT]

Re: High accuray VCO design

Use the osillator inside the CD4046.
It is very linear and it works good in taht frequency range.
It requires two resistors and a capacitor.
See the application notes.

Mandi

 

[opamp741]

Re: High accuray VCO design

hi Mandi,
Thanx for ur effort..I m looking for VLSI implementation of VCO.
thanx

 

[Teddy]

Re: High accuray VCO design

How the VCO will be controlled? What the Vcotrol range will be?

 

[Btrend]

Re: High accuray VCO design

Hello,
Plz suggest me the architecture of VCO with following specs.

Freq range : 400-600KHz
Accuracy : 2% (i think this is too tough to meet but still the customer wants such accuracy)
Limit : only one high accuracy external component (R/C) is allowed
Technology : CMOS 1.2V

Thanx
Opamp741

I think the frequency range is too low for VLSI implementation, u will need a
large area to make the delay cell (ring oscillator ).
why don't u enlarge the frequency range to 400*20 ~ 600*20 KHz, and then divide the VCO by 20 !?

 

[opamp741]

Re: High accuray VCO design

OK, the frequency range cud be made to 400*20 ~ 600*20 KHz.
but how to get 2% accuracy with a components variation of 20%.
can someone give some idea abt accurate tuning of RC delay.

 

[extraord]

Re: High accuray VCO design

the frequency is ok the area will not be larger than a Pad.
but the spec is so tough.
if the temperature is various from -40 to 125, almost impossible.
maybe bandgap can help you. or laser trimming resistor.