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LTC2358-16

Rev A

For more information www.analog.com

with 100Ω characteristic impedance. Logical 1’s and 0’s

are nominally represented by differential +350mV and

−350mV,respectively.Forclarity,allLVDStimingdiagrams

and interface discussions adopt the logical rather than

physical convention.

As shown in Figure 19, in LVDS I/O mode the serial data

bus consists of a serial clock differential input, SCKI, serial

data differential input, SDI, serial clock differential output,

SCKO, and serial data differential output, SDO. Communi-

cation with the LTC2358-16 across this bus occurs during

predefined data transaction windows. Within a window,

the device accepts 24-bit SoftSpan configuration words

for the next conversion on SDI and outputs 24-bit packets

containing conversion results and channel configuration

information from the previous conversion on SDO. New

data transaction windows open 10ms after powering up

or resetting the LTC2358-16, and at the end of each con-

version on the falling edge of BUSY. In the recommended

use case, the data transaction should be completed with

a minimum tQUIET time of 20ns prior to the start of the

next conversion, as shown in Figure 19. New SoftSpan

configuration words are only accepted within this recom-

mended data transaction window, but SoftSpan changes

take effect immediately with no additional analog input

settling time required before starting the next conversion.

It is still possible to read conversion data after starting the

nextconversion,butthiswilldegradeconversionaccuracy

and therefore is not recommended.

Just prior to the falling edge of BUSY and the opening of

a new data transaction window, SDO is updated with the

latestconversionresultsfromanaloginputchannel0.Both

rising and falling edges on SCKI serially clock conversion

resultsandanaloginputchannelconfigurationinformation

out on SDO. SCKI is also echoed on SCKO, skew-matched

Figure 19. Serial LVDS I/O Mode

APPLICATIONS INFORMATION

S23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

25 26

S22 S21 S20 S19 S18 S17 S16 S15 S14 S13 S12 S11 S10 S9 S8 S7 S6 S5

D15

D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 0 0

SS1

SS2

SS0 D15 D14 D13

CNV

(CMOS)

CS = PD = 0

235816 F19

DON’T CARE

tACQ

BUSY

(CMOS)

SCKO

(LVDS)

SDO

(LVDS)

SCKI

(LVDS)

SDI

(LVDS)

DON’T CARE

SAMPLE N

tCNVL

tCYC

RECOMMENDED DATA TRANSACTION WINDOW

SAMPLE N + 1

SoftSpan CONFIGURATION WORD FOR CONVERSION N + 1

CHANNEL 0

24-BIT PACKET

CONVERSION N

CHANNEL 1

24-BIT PACKET

CONVERSION N

CHANNEL 7

24-BIT PACKET

CONVERSION N

CONVERSION RESULT

CHANNEL ID SoftSpan

186

185

187 188 189 190 191 192

SS1

SS2

SS0 D15

CHANNEL 0

24-BIT PACKET

CONVERSION N

CONVERSION

RESULT

CHANNEL ID SoftSpan

tSKEW

tCNVH

tSCKIH

tSCKIL

tBUSYLH

tDSDOSCKI

tHSDOSCKI

tDSDOBUSYL

tSSDISCKI

tHSDISCKI

tQUIET

tSCKI

tCONV

C2 C1 C0

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