AD9516-2SLASHPCBZ datasheet(67/84 Pages) AD

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AD9516-2

Rev. 0 | Page 67 of 84

Reg.

Addr

(Hex) Bit(s) Name

Description

<3>

LD Pin

Comparator

Enable

Enables the LD pin voltage comparator. This is used with the LD pin current source lock detect mode.

When in the internal (automatic) holdover mode, this enables the use of the voltage on the LD pin to

determine if the PLL was previously in a locked state (see Figure 51). Otherwise, this can be used with

the REFMON and STATUS pins to monitor the voltage on this pin.

<3> = 0; disable LD pin comparator; internal/automatic holdover controller treats this pin as true (high).

<3> = 1; enable LD pin comparator.

<2>

Holdover

Along with <0> enables the holdover function.

Enable

<2> = 0; holdover disabled.

<2> = 1; holdover enabled.

<1>

External

Enables the external hold control through the SYNC pin. (This disables the internal holdover mode.)

Holdover

<1> = 0; automatic holdover mode—holdover controlled by automatic holdover circuit.

Control

<1> = 1; external holdover mode—holdover controlled by SYNC pin.

<0>

Holdover

Along with <2> enables the holdover function.

Enable

<0> = 0; holdover disabled.

<0> = 1; holdover enabled.

<6>

VCO Cal

Readback register: status of the VCO calibration.

Finished

<6> = 0; VCO calibration not finished.

<6> = 1; VCO calibration finished.

<5>

Holdover

Active

Readback register: indicates if the part is in the holdover state (see Figure 51). This is not the same as

holdover enabled.

<5> = 0; not in holdover.

<5> = 1; holdover state active.

<4>

REF2

Readback register: indicates which PLL reference is selected as the input to the PLL.

Selected

<4> = 0; REF1 selected (or differential reference if in differential mode).

<4> = 1; REF2 selected.

<3>

VCO

Frequency >

Readback register: indicates if the VCO frequency is greater than the threshold (see Table 16, REF1, REF2, and

VCO Frequency Status Monitor).

Threshold

<3> = 0; VCO frequency is less than the threshold.

<3> = 1; VCO frequency is greater than the threshold.

<2>

REF2

Frequency >

Readback register: indicates if the frequency of the signal at REF2 is greater than the threshold frequency

set by Register 0x1A<6>.

Threshold

<2> = 0; REF2 frequency is less than threshold frequency.

<2> = 1; REF2 frequency is greater than threshold frequency.

<1>

REF1

Frequency >

Readback register: indicates if the frequency of the signal at REF2 is greater than the threshold frequency

set by Register 0x1A<6>.

Threshold

<1> = 0; REF1 frequency is less than threshold frequency.

<1> = 1; REF1 frequency is greater than threshold frequency.

<0>

Digital Lock

Readback register: digital lock detect.

Detect

<0> = 0; PLL is not locked.

<0> = 1; PLL is locked.

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