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LTC2335-18

233518f

For more information www.linear.com/LTC2335-18

Figure 16. Power Dissipation of the LTC2335-18

Decreases with Decreasing Sampling Frequency

applicaTions inForMaTion

Power Dissipation vs Sampling Frequency

When nap mode is employed, the power dissipation of

the LTC2335-18 decreases as the sampling frequency is

reduced, as shown in Figure 16. This decrease in aver-

age power dissipation occurs because a portion of the

LTC2335-18 circuitry is turned off during nap mode, and

the fraction of the conversion cycle (tCYC) spent napping

increases as the sampling frequency (fSMPL)isdecreased.

DIGITAL INTERFACE

TheLTC2335-18featuresCMOSandLVDSserialinterfaces,

selectable using the LVDS/CMOS pin. The flexible OVDD

supply allows the LTC2335-18 to communicate with any

CMOSlogicoperatingbetween1.8Vand5V,including2.5V

and 3.3V systems, while the LVDS interface supports low

noise digital designs. Together, these I/O interface options

enable the LTC2335-18 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 serial data output,

SDO. Communication with the LTC2335-18 across this

bus occurs during predefined data transaction windows.

Within a window, the device accepts control words on SDI

to configure the SoftSpan range and channel for the next

conversionandprogramthesequencer,andoutputs24-bit

packetscontainingtheconversionresultandconfiguration

information from the previous conversion on SDO.

Figure 17. Serial CMOS I/O Mode, Direct Per-Conversion Configuration

15 16

18 19

C6 C5 C4 C3 C2 C1 C0

D17

D16 D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1

D17

CNV

CS = PD = 0

DON’T CARE

tACQ

BUSY

SCKO

SDO

SCKI

SDI

DON’T CARE

SAMPLE N

RECOMMENDED DATA TRANSACTION WINDOW

SAMPLE N + 1

CONTROL WORD FOR CONVERSION N + 1

24-BIT PACKET CONVERSION N

(REPETITION)

CONVERSION RESULT

CHANNEL ID

SoftSpan

CONVERSION RESULT

CH2 CH1 CH0

SS1

SS2

SS0

tSSDISCKI

tHSDOSCKI

tDSDOSCKI

tBUSYLH

tHSDISCKI

tSCKIH

tQUIET

tSCKIL

tDSDOBUSYL

tCNVH

tSKEW

tCONV

tCNVL

tCYC

233518 F17

tSCKI

IOVDD

IVDD

IVEE

IVCC

WITH NAP MODE

t CNVL = 500ns

SAMPLING FREQUENCY (kHz)

200

400

600

800

1000

–6

–4

–2

233518 F16

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