LTC2415-1IGN datasheet(16/40 Pages) LINER

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LTC2415/LTC2415-1

sn2415 24151fs

APPLICATIO S I FOR ATIO

Frequency Rejection Selection LTC2415 (FO)

The LTC2415 internal oscillator provides better than 110dB

normal mode rejection at the line frequency and its harmon-

ics for 50Hz

±2% or 60Hz ±2%. For 60Hz rejection, FO

should be connected to GND while for 50Hz rejection the FO

pin should be connected to VCC.

The selection of 50Hz or 60Hz rejection can also be made by

driving FO to an appropriate logic level. A selection change

during the sleep or data output states will not disturb the

converter operation. If the selection is made during the

conversion state, the result of the conversion in progress

may be outside specifications but the following conver-

sions will not be affected.

When a fundamental rejection frequency different from

50Hz or 60Hz is required or when the converter must be

synchronized with an outside source, the LTC2415 can

operate with an external conversion clock. The converter

automatically detects the presence of an external clock

signal at the FO pin and turns off the internal oscillator. The

frequency fEOSC of the external signal must be at least

2560Hz (1Hz notch frequency) to be detected. The external

clock signal duty cycle is not significant as long as the

minimum and maximum specifications for the high and low

periods tHEO and tLEO are observed.

While operating with an external conversion clock of a

frequency fEOSC, the LTC2415 provides better than 110dB

normal mode rejection in a frequency range fEOSC/2560

±4% and its harmonics. The normal mode rejection as a

function of the input frequency deviation from fEOSC/2560

is shown in Figure 7a.

Whenever an external clock is not present at the FO pin, the

converter automatically activates its internal oscillator and

enters the Internal Conversion Clock mode. The LTC2415

operation will not be disturbed if the change of conversion

clock source occurs during the sleep state or during the

data output state while the converter uses an external serial

clock. If the change occurs during the conversion state, the

result of the conversion in progress may be outside speci-

fications but the following conversions will not be affected.

If the change occurs during the data output state and the

converter is in the Internal SCK mode, the serial clock duty

cycle may be affected but the serial data stream will remain

valid.

Table 3a summarizes the duration of each state and the

achievable output data rate as a function of FO.

Frequency Rejection Selection LTC2415-1 (FO)

The LTC2415-1 internal oscillator provides better than

87dB normal mode rejection over the range of 49Hz to

61.2Hz as shown in Figure 7b. For simultaneous 50Hz/60Hz

rejection, FO should be connected to GND.

In order to achieve 87dB normal mode rejection of 50Hz

±2% and 60Hz ±2%, two consecutive conversions must be

averaged. By performing a continuous running average of

the two most current results, both simultaneous rejection

is achieved and a 2

× increase in throughput is realized

relative to the LTC2413 (see Normal Mode Rejection, Ouput

Rate and Running Averages sections of this data sheet).

When a fundamental rejection frequency different from

the range 49Hz to 61.2Hz is required or when the converter

must be synchronized with an outside source, the

LTC2415-1 can operate with an external conversion clock.

The converter automatically detects the presence of an

external clock signal at the FO pin and turns off the internal

oscillator. The frequency fEOSC of the external signal must

be at least 2560Hz to be detected. The external clock signal

duty cycle is not significant as long as the minimum and

maximum specifications for the high and low periods, tHEO

and tLEO, are observed.

While operating with an external conversion clock of a

frequency fEOSC, the LTC2415-1 provides better than

110dB normal mode rejection in a frequency range fEOSC/

2560

±4%. The normal mode rejection as a function of the

input frequency deviation from fEOSC/2560 is shown in

Figure 7a and Figure 7c shows the normal mode rejection

with running averages included.

Whenever an external clock is not present at the FO pin the

converter automatically activates its internal oscillator and

enters the Internal Conversion Clock mode. The LTC2415-1

operation will not be disturbed if the change of conversion

clock source occurs during the sleep state or during the

data output state while the converter uses an external

serial clock. If the change occurs during the conversion

state, the result of the conversion in progress may be

outside specifications but the following conversions will

not be affected. If the change occurs during the data output

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