5.5 Zero Delay Mode
A zero delay mode is available for applications that require fixed and consistent minimum delay between the selected input and outputs.
The zero delay mode is configured by opening the internal feedback loop through software configuration and closing the loop externally.
This helps to cancel out the internal delay introduced by the dividers, the crosspoint, the input, and the output drivers. Any one of the
outputs can be fed back to the FB_IN pins, although using the output driver that achieves the shortest trace length will help to minimize
the input-to-output delay. The OUT9 and FB_IN pins are recommended for the external feedback connection in the Si5341. OUT3
and FB_IN pins are recommended for the external feedback in the Si5340. The FB_IN input pins must be terminated and ac-coupled
when zero delay mode is used. A differential external feedback path connection is necessary for best performance. For this reason,
customers should avoid using CMOS outputs for driving the external feedback path. Zero Delay Mode performance will degrade with
low values of phase detector frequency (Fpfd). For this reason, ClockBuilder Pro will not enable Zero Delay Mode with an Fpfd of less
than 128 kHz.
When the DSPLL is set for Zero-Delay Mode (ZDM), a hard reset request from either the RSTb pin or RST_REG register bit will have a
delay of ~750 ms before executing. Any subsequent register writes to the device should be made after this time expires or they will be
overwritten with the NVM values. Please contact Silicon Labs technical support for information on reducing this ZDM hard reset time.
VDDO7
OUT7
OUT7
÷R
7
OUT0
VDDO0
OUT0
÷R
0
Si5341
IN0
IN0
IN1
IN1
IN2
IN2
÷P
1
÷P
0
÷P
2
DSPLL
LPF
PD
÷M
15GHz
IN3/FB_IN
÷P
3
100
IN3/FB_IN
÷N
0
÷N
1
÷N
2
÷N
3
OUT2
VDDO2
OUT2
÷R
2
External Feedback Path
OUT1
VDDO1
OUT1
÷R
1
OUT8
VDDO8
OUT8
÷R
8
OUT9
VDDO9
OUT9
÷R
9
÷5
÷N
4
Si5341 Zero Delay Mode Setup
The following table gives the register used for the Zero Delay mode.
Si5341, Si5340 Rev D Family Reference Manual • Output Clocks
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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Rev. 1.3 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 26, 2021
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