AWR2243-2X-CAS-EVM: How to design the 20GHz SYNC for cascade radar with resistors?

Jesse Wang

Part Number: AWR2243-2X-CAS-EVM
Other Parts Discussed in Thread: LMK1C1102, LMK00334-Q1, LMK00334, LMK00804B-Q1

Tool/software:

Hi TI expert,

In TI's reference design on https://www.ti.com/tool/AWR2243-2X-CAS-EVM, due to we can't find the automotive grade Q100 certified clock buffer (PS: the reference design uses "LM686x0-Q1 70V, 8A/6A/4A, Automotive Buck Converters Optimized for Safety-Relevant Applications datasheet" which is not automotive grade), we will like to use resistors as divider for sharing the 20GHz Sync signals as below picture.

Is the connection of the Sync signals directly as below ok?

if this connection is fine, please advise the value of “R” and layout guide TI suggested.

BR, Jesse.

26 days ago

0 E. Shareef 25 days ago

TI__Genius 16310 points

Hello Jesse,

Let me discuss internally and get back to you on this query.

-E. Shareef

0 E. Shareef 25 days ago in reply to E. Shareef

TI__Genius 16310 points

Hello Jesse,

Why is LM686x0-Q1 not an Automotive part? It is AEC-Q100 qualified part.

-E. Shareef

0 tommy tang 24 days ago in reply to E. Shareef

Prodigy 60 points

Some mistake here, not LM686x0-Q1, LMK1C1102PWR is the buffer used in EVM design but not an automotive part.

0 E. Shareef 23 days ago in reply to tommy tang

TI__Genius 16310 points

Ok. I will repond in some time.

0 tommy tang 13 days ago

Prodigy 60 points

Hi Shareef,

Any feedback on this one?

0 E. Shareef 12 days ago in reply to tommy tang

TI__Genius 16310 points

Hello,

The specific characteristics and functionality you're looking for in a replacement part (e.g., signal frequency range, timing specifications, etc.), is difficult to match using a resistor divider.

Some possible alternatives could be:

IDT (Integrated Device Technology) offers a range of synchronous clock buffers, such as the VCU1063, which is AEC-Q100 certified.
Intersil/MAXIM Integrated also provides qualified automotive-grade clock buffer solutions like the ISOC1101, which might fit your requirements.

Give a couple days to provide a better solution.

Thanks,

E. Shareef

0 E. Shareef 10 days ago in reply to E. Shareef

TI__Genius 16310 points

Hello,

Adding to above, the reaons I would NOT recommend a resistor divider is

Resistor dividers are passive and can distort high-speed signals due to impedance mismatch, reflections, and slow edge rates.
LMK1C1102 preserves signal integrity with low additive jitter and fast edge rates, which is critical for clock signals in high-speed applications.

Resistor dividers can't drive multiple loads or long traces effectively.
LMK1C1102 provides strong output drivers capable of driving multiple clock inputs with consistent voltage levels.

Clock buffers like LMK1C1102 are designed for timing-critical applications, with guaranteed specs for jitter, skew, and propagation delay.
Resistor dividers are not predictable under varying conditions (temperature, load, etc.).

0 E. Shareef 10 days ago in reply to E. Shareef

TI__Genius 16310 points

Alternative parts to LMK1C1102

LMK00334-Q1
- Automotive-grade version of LMK00334
- Supports LVCMOS and differential outputs
- Low additive jitter suitable for high-speed clocking
- AEC-Q100 qualified
LMK00804B-Q1
- 4-output LVCMOS clock buffer
- Designed for automotive and industrial use
- Low jitter, wide voltage support
- AEC-Q100 qualified

0 tommy tang 9 days ago

Prodigy 60 points

Hi Shareef,

Sorry, I just notice that the question is not correct, the question is for frame sync signal, not for 20GHz sync signal, please help to re-advise on this, thanks a lot.

BTW, we will use wilkinson power divider for the 20GHz sycn signal.