How to design programmable osc

[stoned]

Hi all,
This osc feature is : output frequency is 1MHz~30MHz; and controlled by 5 bit , on the hand, has 32 steps between 1 and 30, for example 00000 correspond to 1M 11111 correspond to 30MHz.

first, i want to design this by VCO, and the control voltage of VCO is controlled by the 5 bits. But VCO output frequency's variation is too much for PVT.
when used PLL for output , variation is cancelled, but the cost is too much.

How to do this? can anyone give me some advice, thanks.

Stoned

 

[electronspin]

what about creating a 30MHz xtal oscillator followed by a 5 bit programmable counter. Voila!

 

[stoned]

what about creating a 30MHz xtal oscillator followed by a 5 bit programmable counter. Voila!

if this method has to use crystal?
but the chip only have 6 pins 2 power pins, 4 bits control pin.

 

[ricklin]

I think it's very difficult to get accurate frequency inside chip without feedback or xtal circuit.