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LTC2348-16

234816fa

For more information www.linear.com/LTC2348-16

applicaTions inForMaTion

DIGITAL INTERFACE

TheLTC2348-16featuresCMOSandLVDSserialinterfaces,

selectable using the LVDS/CMOS pin. The flexible OVDD

supply allows the LTC2348-16 to communicate with any

CMOS logic operating between 1.8V and 5V, including

2.5V and 3.3V systems, while the LVDS interface supports

low noise digital designs. In CMOS mode, applications

may employ between one and eight lanes of serial data

output, allowing the user to optimize bus width and data

throughput. Together, these I/O interface options enable

the LTC2348-16 to communicate equally well with legacy

microcontrollers and modern FPGAs.

Serial CMOS I/O Mode

As shown in Figure 17, in CMOS I/O mode the serial data

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

input, SDI, serial clock output, SCKO, and eight lanes of

serial data output, SDO0 to SDO7. Communication with

the LTC2348-16 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 SDO0 to SDO7. New

data transaction windows open 10ms after powering up

or resetting the LTC2348-16, 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 17. 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.

C2 C1 C0

S23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

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

CNV

CS = PD = 0

DON’T CARE

tACQ

BUSY

SDO7

SCKO

SDO0

SCKI

SDI

DON’T CARE

SAMPLE N

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

CHANNEL 0

24-BIT PACKET

CONVERSION N

234816 TD01

CONVERSION RESULT

CHANNEL ID SOFTSPAN

CONVERSIONRESULT

D15

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

SS1

SS2

SS0 D15

DON’T CARE

CONVERSION RESULT

CHANNEL ID SOFTSPAN

CONVERSIONRESULT

tSCKI

tSCKIH

tBUSYLH

tSCKIL

tHSDOSCKI

tDSDOSCKI

tSSDISCKI

tQUIET

tHSDISCKI

tDSDOBUSYL

tCNVH

tSKEW

tCONV

tCNVL

tCYC

Figure 17. Serial CMOS I/O Mode

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