Part Number: TCAN1044AEV-Q1
Hi team,
When using split termination with TCAN1044AEV-Q1, how can we calculated CSPLIT value?
SLLA270 mentions CSPLIT=4.7nF with 1.1Mbps. How can we determine CSPLIT when the data rate is 4Mbps with RL=120ohm?
Best regards,
Kurumi
Hi Kurumi,
I believe calculating the recommended split capacitance comes from the equation in figure 10 in SLLA270,
We can re-arrange the equation to say CL = 1 / (2*pi*R*fc). Multiply CL, divide by fc.
A key idea to note in this application note is that the cutoff frequency fc is measured in Hz. If we desire a 1.1Mbps CAN signal, this means we are operating about 1.1Mbps / 2 = 550 kHz with termination of R = 60ohm, the low-pass filter equation becomes the following.
CL = 1 / (2*pi*60*550kHz) = ~4.823 nF.
Choose standard capacitor sizing of 4.7 nF.
Now with the customer requirements, is RL the size of each split resistor (2 x 120 ohm resistors), or is it 60ohm and 60hm like figure 10?
I can do the calculation for both cases.
fc = 4Mbps / 2 = 2MHz
RL = 120 ohm
CL = 1 / (2*pi*120*2MHz) = ~ 0.663 nF
fc = 4Mbps / 2 = 2MHz
RL = 60 ohm
CL = 1 / (2*pi*60*2MHz) = ~1.33 nF
Regards,
Tyler
