LM76003: Oscillator spec

Hi Oba,

Yes you can use a higher tolerance resistor for the RT set frequency. It is just the value on the datasheet is guaranteed using the 0.1% resistor.
Therefore you can expect a larger deviation with a higher tolerance frequency. Unfortunately we do not have the data using a higher tolerance resistor. But maybe you can have some approximation from equation 6 in the datasheet
www.ti.com/.../lm76003.pdf

I hope that helps
Thanks
-Arief

Hello Arief,

Thanks for your reply.
This is just confirmation.
Can we guarantee all operation except for oscillation frequency with 133KOhm+-2%?
How much tolerance of resistor can be allowed for 133KOhm?
I mean how to think about the largest resistance value (means lowest frequency) that can be connected?

Also regarding min frequency when using 133KOhm+-2%,

From equation 6 in the datasheet,
Frequency = 38400/Rt - 14.33

When 133K(0.1%), the frequency = 302.763 - 303.341KHz. From the datasheet, we guarantee 270-330KHz in this case.
When 133K(2%), the frequency = 297.391 - 308.944KHz. So 297.391 * (270/302.763) = 265.209 KHz. This value may be min frequency.
Does this make sense?

Regards,
Oba

Hi Oba,

Normally i just use a 1% resistor into the RT. If you like a tighter tolerance maybe you can use the SYNC.
All of our bench validation for this part is done with 1% resistor, therefore for operational purpose there should be no issue with using a 1% resistor in this case.

The guarantee spec is only if you use the 0.1% resistor as shown on the EC table and this spec is over temperature.

The equation is used only for approximation and i think it is only for room temperature.

I hope that helps

Thanks
-Arief

Hello Arief

Thanks.

I’m a little bit confused about what we guarantee.

I think there are two different things.

One is only oscillator itself. It means just guarantee for oscillation frequency.

I understand oscillation “frequency” can be only guaranteed with 133Kohm+-0.1%.

0.5% or 2% can be used for Rt but we don’t know the oscillation frequency with them.  I think I understand it.

The other is whole device operation.

This is my unclear point. My concern is especially minimum frequency that we can guarantee whole device operation. The data sheet said that this device support only over 300MHz operation. Actually 270MHz  seemed be accepted.But how about under 270MHz? With 2% Rt resistor, it may be under 270MHz. Can we guarantee the device operation with it?

I would like to know especially 2% case. I understand we don’t know the exact osicillation frequency, but can we guarantee the device operation in this case?

Regards,

Oba