LTC2483 datasheet(9/20 Pages) LINER

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LTC2450-1

24501fb

Conversion Status Monitor

For certain applications, the user may wish to monitor

the LTC2450-1 conversion status. This can be achieved

by holding SCK HIGH during the conversion cycle. In

this condition, whenever the CS input pin is pulled low

(CS = LOW), the SDO output pin will provide an indication

of the conversion status. SDO = HIGH is an indication of

a conversion cycle in progress while SDO = LOW is an

indication of a completed conversion cycle. An example

of such a sequence is shown in Figure 4.

Conversionstatusmonitoring,whilepossible,isnotrequired

for LTC2450-1 as its conversion time is ﬁxed and equal at

approximately 16.6ms (21ms maximum). Therefore, ex-

ternal timing can be used to determine the completion of a

conversion cycle.

SERIAL INTERFACE

The LTC2450-1 transmits the conversion result and receives

the start of conversion command through a synchronous

3-wire interface. This interface can be used during the

CONVERT and SLEEP states to assess the conversion

status and during the DATA OUTPUT state to read the

conversion result, and to trigger a new conversion.

APPLICATIONS INFORMATION

Serial Interface Operation Modes

The following are a few of the more common interface

operation examples. Many more valid control and serial

data output operation sequences can be constructed based

upon the above description of the function of the three

digital interface pins.

The modes of operation can be summarized as follows:

1) The LTC2450-1 functions with SCK idle high (commonly

known as CPOL = 1) or idle low (commonly known as

CPOL = 0).

2) After the 16th bit is read, the user can choose one of

two ways to begin a new conversion. First, one can

pull CS high (CS = ↑). Second, one can use a high-low

transition on SCK (SCK = ↓).

3) At any time during the Data Output state, pulling CS

high (CS = ↑) causes the part to leave the I/O state,

abort the output and begin a new conversion.

4) When SCK = HIGH, it is possible to monitor the conver-

sion status by pulling CS low and watching for SDO

to go low. This feature is available only in the idle-high

(CPOL = 1) mode.

Figure 4. Conversion Status Monitoring Mode

SLEEP

SDO

SCK = HI

CONVERT

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