AK8186B Datasheet, PDF (29/69 Pages) Asahi Kasei Microsystems – Multi Output Clock Generator with Integrated 2.0GHz VCO

AK8186B
Table 22 Setting the channel divider to ignore the SYNC
Divider
Nosync
Value to
register bit
ignore SYNC pin
0
0x191[6]
1
1
0x194[6]
1
2
0x197[6]
1
3
0x19C[3]
1
4
0x1A1[3]
1
Automatic Holdover Mode
An automatic holdover puts the charge pump into a high impedance state immediately when the unlock
state is detected. A flow chart of the automatic holdover function is shown in Figure 16.
Getting into the holdover
Condition
: LD pin = H when DLD = low (false)
Operation Timing : immediately
Operation
: puts the charge pump into a high impedance state
Leaving the holdover
Condition
: DLD = High (true)
Operation Timing : synchronous with a first PFD rising edge after DLD goes high.
Operation
: puts the charge pump into a normal state, resets the B-counter.
LD pin is able to report the status of DLD, ALD and CLD. The CLD is recommended to use for the automatic
holdover to avoid re-triggering a holdover due to chattering on the LD. The register 0x1A[5:0] defines the
function of the LD.
The auto holdover function uses the LD pin comparator to sense the status of the LD pin. When the register
0x1D[3]=0, the LD comparator is disabled and the LD pin is treated as always high by the automatic
holdover function. When 0x1D[3]=1, the LD comparator is enabled and can be used for DLD, ALD and CLD.
The registers shown in Table are required to be set to use the automatic holdover function.
Table 23 Setting Automatic Holdover Function
Register
Name
0x18<6:5>
Lock Detect Counter
0x18[3]
Disable Digital Lock Detect
0x1A[5:0]
LD pin Control
0x1D[3]
LD pin Comparator Enable
0x1D[1]
0x1D[2][0]
External Holdover Control
Holdover Enable
Description
Select PFD cycles to determine lock.
Set 0 to operate normally.
Set 04h to select Current source lock detect if
using the LD pin comparator.
Set 1 if using. When set 0 (disabled), the
automatic holdover function treats the LD pin
as always high.
Set 0 to use the automatic holdover function.
Set 1 to enable holdover.
draft-E-02
- 29 -
Sep-2012