LTM2893 datasheet(24/32 Pages) LINER

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LTM2893/LTM2893-1

28931fb

For more information www.linear.com/LTM2893

TIMING DIAGRAMS

Figure 11. Isolated Side Read and Write to ADC (LTM2893-1)

28931ADC CYCLE TIMEMIN = tDCNV + tCNV2toADCstart

+ tCNVADC + tBUSY2FBUSYF + tBUSYFSCKR + tDATAREAD +

tSCKSSDIS + tCRC + tQUIET + tADDISODELAY. Reference SAM-

PLING RATE section.

where:

If wordcount =1:

tADDISODELAY = (2 + WORDLENGTH) • tSCK2

If wordcount ≥ 2:

tADDISODELAY = 2 • (2 + WORDLENGTH) • tSCK2

SAFE REGIONS OF THE SELECT ENABLE SIGNALS

The select enable signals SA, SB, and SC must be limited

in use to transition in a fixed set of safe regions. Transi-

tions within the collision regions may cause data loss or

timing loss to important conversion or result information.

If the SA2, SB2, or SC2 are configured as inputs, do not

change 150ns prior to the SS2 signal falling. The SS2

signal fall is triggered by BUSY2 or BUSYS falling. If one

of these signals changes in this collision region, the SPI

process will be corrupted.

CNV2

BUSY2

ADC CONVERSION READ AND WRITE TIMING DIAGRAM ISOLATED SIDE INTERFACE

SS2

SCK2

MISOA2,

MISOB2

DI17

ADC CONVERSION TIME

DI0

ADC CYCLE TIME

ADC ACQUISITION TIME

MOSI2

D17

ADC RESULT

ADC CONFIGURATION

tDMOSI2

tHDMOSI2

tSS2FMOSI2

XXXXXXXX

2893 F11

Figure 12. Select Signals Safe Transition Regions

SA, SB, SC SAFE TRANSITION REGIONS

SAFE

150ns

CNV

COLLISION

POSSIBLE

LOSS OF DATA

SPI TRANSACTION

DO NOT

CHANGE 40ns

AFTER

CONVERSION

SA, SB, SC PROCESS DELAYED

COLLISION

POSSIBLE

LOSS OF DATA

150ns

SA, SB, SC

BUSY

SAFE, ADDS NOISE

2893 F12

COLLISION

POSSIBLE

LOSS OF DATA

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