RF Layout Reference Design of CC1200 for 420-470 MHz

Nomo

Other Parts Discussed in Thread: CC1200

Hello,

I have some questions for the RF Layout Reference Design of CC1200 for 420-470MHz.

1. For the PA bias circuit, please let me know the purpose of R171, C173 and L171.
Especially, I want to know the purpose of C173.
Also, if I need to do impedance matching for the circuit, how should I decide the register value, capacitance value and inductance value?

2. In case L173 (inductance for impedance matching) is changed from wound coil to lamination coil, could you teach me the care points?

Best Regards,

Nomoto

over 10 years ago

0 Sverre over 10 years ago

TI__Mastermind 39860 points

The PA load is L171. R171 is used to lower the dc operating point and thus allow a higher drain-source voltage swing (and hence output power) without violating the maximum drain-source process limits.

There is no need to do impedance matching. Follow the reference design! Copy the component values as well as the PCB layout. We have spent a lot of time optimizing this design in our lab and with all due respect I do not think you will be able to get any better performance than given in the data sheet.

Changing the L173 inductor will most likely reduce the output power slightly (0.5 dB?). Q-factor is important.

0 Nomo over 10 years ago in reply to Sverre

Guru 16800 points

Hello Sverre-san,

Thank you for your reply.
How about the usage of C173?

Best Regards,

Nomoto

0 Nomo over 10 years ago in reply to Sverre

Guru 16800 points

Hello,

Have you any update on my thread?

Best Regards,

Nomoto

0 Sverre over 10 years ago in reply to Nomo

TI__Mastermind 39860 points

The resistor lowers the dc operating point. The capacitor makes the resistor "invisible" at RF and thus allow maximum voltage swing.

0 Nomo over 10 years ago in reply to Sverre

Guru 16800 points

Hello Sverre-san,

Thank you for your reply.
Your comment helps me.

Best Regards,

Nomoto

Sub-1 GHz

Sub-1 GHz forum

RF Layout Reference Design of CC1200 for 420-470 MHz