LTC4332 remote SCLK faster than local

Question

Our use of the LTC4332s is based on the example application circuit within the datasheet. Both local and remote are set to the 2MHz clock via SPEED1 and SPEED2 pins, yet when measuring the REMOTE_SCK signal, we see around 2.16Mhz, while the MCU_SCK is correctly being fed a nice 2.000MHz.

Are there any known issues running at 2MHz that would cause the remote side to have a faster clock? Perhaps specific components/circuit layout/register settings need to be applied at this speed?

ericb · Accepted Answer

HI, 
 Sorry about the delay in the response. 
 The SPEEDx pins only set the speed of the internal data link between the local and remote LTC4332 devices. 
 The remote SCK timing is generated from the sampling of the local SCK which is related to the SPEEDx setting. This is why the SPEEDx needs to be equal or greater than the local SCK frequency. The locally sampled SCK is then communicated across the internal data link to the remote LTC4332. Because of timing jitter, its possible that the remote SCK timing/frequency will vary from the local SCK timing/frequency; however, with a large enough averaging window, the remote SCK frequency should not exceed the local SCK frequency. 
 Eric)

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LTC4332 remote SCLK faster than local

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