LTC2436-1IGN datasheet(11/28 Pages) LINER

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LTC2436-1

24361f

below –FS, the conversion result is clamped to the value

corresponding to –FS – 1LSB.

Simultaneous Frequency Rejection

The LTC2436-1 internal oscillator provides better than

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

61.2Hz as shown in Figure 4. For this simultaneous 50Hz/

60Hz rejection, FO should be connected to GND.

When a fundamental rejection frequency different from

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

must be sychronized with an outside source, the LTC2436-1

can operate with an external conversion clock. The conveter

Table 2. LTC2436-1 Output Data Format

Differential Input Voltage

Bit 18

Bit 17

Bit 16

Bit 15

Bit 14

Bit 13

Bit 12

…

Bit 0

VIN*

EOC

CH0/CH1

SIG

MSB

VIN* ≥ 0.5 • VREF**

0/1

…

0.5 • VREF** – 1LSB

0/1

…

0.25 • VREF**

0/1

…

0.25 • VREF** – 1LSB

0/1

…

0/1

…

–1LSB

0/1

…

– 0.25 • VREF**

0/1

…

– 0.25 • VREF** – 1LSB

0/1

…

– 0.5 • VREF**

0/1

…

VIN* < –0.5 • VREF**

0/1

…

*The differential input voltage VIN = IN+ – IN–.

**The differential reference voltage VREF = REF+ – REF–.

Figure 4. LTC2436-1 Normal Mode

Rejection When Using an Internal Oscillator

DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)

24361 F04

–80

–90

–100

–120

–130

–140

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,theLTC2436-1providesbetterthan110dB

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 5.

APPLICATIO S I FOR ATIO

Figure 5. LTC2436-1 Normal Mode Rejection When

Using an External Oscillator of Frequency fEOSC

DIFFERENTIAL INPUT SIGNAL FREQUENCY

DEVIATION FROM NOTCH FREQUENCY fEOSC/2560(%)

–12

–8

–4

048

24361 F05

–80

–85

–90

–95

–100

–105

–110

–115

–120

–125

–130

–135

–140

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