LTC2410_15 Datasheet, PDF (15/48 Pages) Linear Technology – 24-Bit No Latency ADC with Differential Input and Differential Reference

LTC2410
APPLICATIO S I FOR ATIO
synchronized with an outside source, the LTC2410 can
operate with an external conversion clock. The converter
automatically detects the presence of an external clock
signal at the F_O pin and turns off the internal oscillator. The
frequency f_EOSC of the external signal must be at least
2560Hz (1Hz notch frequency) to be detected. The exter-
nal clock signal duty cycle is not significant as long as the
minimum and maximum specifications for the high and
low periods t_HEO and t_LEO are observed.
While operating with an external conversion clock of a
frequency f_EOSC, the LTC2410 provides better than 110dB
normal mode rejection in a frequency range f_EOSC/2560
±4% and its harmonics. The normal mode rejection as a
function of the input frequency deviation from f_EOSC/2560
is shown in Figure 4.
Whenever an external clock is not present at the F_O pin, the
converter automatically activates its internal oscillator and
enters the Internal Conversion Clock mode. The LTC2410
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
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.
–80
–85
–90
–95
–100
–105
–110
–115
–120
–125
–130
–135
–140
–12 –8 –4 0
4
8 12
DIFFERENTIAL INPUT SIGNAL FREQUENCY
DEVIATION FROM NOTCH FREQUENCY f_EOSC/2560(%)
2410 F04
Figure 4. LTC2410 Normal Mode Rejection When
Using an External Oscillator of Frequency f_EOSC
Table 3 summarizes the duration of each state and the
achievable output data rate as a function of F_O.
SERIAL INTERFACE PINS
The LTC2410 transmits the conversion results and re-
ceives the start of conversion command through a syn-
chronous 3-wire interface. During the conversion and
sleep states, this interface can be used to assess the
converter status and during the data output state it is used
to read the conversion result.
Table 3. LTC2410 State Duration
State
Operating Mode
CONVERT
Internal Oscillator
External Oscillator
SLEEP
DATA OUTPUT
Internal Serial Clock
External Serial Clock with
Frequency f_SCK kHz
F_O = LOW
(60Hz Rejection)
F_O = HIGH
(50Hz Rejection)
F_O = External Oscillator
with Frequency f_EOSC kHz
(f_EOSC/2560 Rejection)
F_O = LOW/HIGH
(Internal Oscillator)
F_O = External Oscillator with
Frequency f_EOSC kHz
Duration
133ms, Output Data Rate ≤ 7.5 Readings/s
160ms, Output Data Rate ≤ 6.2 Readings/s
20510/f_EOSCs, Output Data Rate ≤ f_EOSC/20510 Readings/s
As Long As CS = HIGH Until CS = LOW and SCK
As Long As CS = LOW But Not Longer Than 1.67ms
(32 SCK cycles)
As Long As CS = LOW But Not Longer Than 256/f_EOSCms
(32 SCK cycles)
As Long As CS = LOW But Not Longer Than 32/f_SCKms
(32 SCK cycles)
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