Datasheet

LTC2413
15
sn2413 2413fs
While operating with an external conversion clock of a
frequency f
EOSC
, the LTC2413 provides better than 110dB
normal mode rejection in a frequency range f
EOSC
/2560
±4%. The normal mode rejection as a function of the input
frequency deviation from f
EOSC
/2560 is shown in Figure 5.
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 LTC2413
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.
Table 3 summarizes the duration of each state and the
achievable output data rate as a function of F
O
.
SERIAL INTERFACE PINS
The LTC2413 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. LTC2413 State Duration
State Operating Mode Duration
CONVERT Internal Oscillator F
O
= LOW 147ms, Output Data Rate ≤ 6.8 Readings/s
Simultaneous 50Hz/60Hz Rejection
External Oscillator F
O
= External Oscillator 20510/f
EOSC
s, Output Data Rate ≤ f
EOSC
/20510 Readings/s
with Frequency f
EOSC
kHz
(f
EOSC
/2560 Rejection)
SLEEP As Long As CS = HIGH Until CS = LOW and SCK
DATA OUTPUT Internal Serial Clock F
O
= LOW As Long As CS = LOW But Not Longer Than 1.83ms
(Internal Oscillator) (32 SCK cycles)
F
O
= External Oscillator with As Long As CS = LOW But Not Longer Than 256/f
EOSC
ms
Frequency f
EOSC
kHz (32 SCK cycles)
External Serial Clock with As Long As CS = LOW But Not Longer Than 32/f
SCK
ms
Frequency f
SCK
kHz (32 SCK cycles)
Figure 5. LTC2413 Normal Mode Rejection When
Using an External Oscillator of Frequency f
EOSC
APPLICATIO S I FOR ATIO
WUU
U
DIFFERENTIAL INPUT SIGNAL FREQUENCY
DEVIATION FROM NOTCH FREQUENCY f
EOSC
/2560(%)
–12–8–404812
NORMAL MODE REJECTION (dB)
2413 F05
–80
–85
–90
–95
–100
–105
–110
–115
–120
–125
–130
–135
–140
48 50 52 54 56 58 60 62
DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)
NORMAL MODE REECTION RATIO (dB)
2413 F04
–80
–90
–100
–100
–120
–130
–140
Figure 4. LTC2413 Normal Mode Rejection
When Using an Internal Oscillator