LV25400W_10 Datasheet, PDF (38/42 Pages) Sanyo Semicon Device – For Automotive Applications DSP Tuner Front End

LV25400W
(2) Dead zone mode characteristics
The table below presents an overview of the characteristics in each of the dead zone modes.
Setting
DZ1
DZ0
Dead zone mode
Charge pump (p/n-channel) state at 0 phase
difference
Dead zone width (for
reference purposes)
0
0
DZA
On/on
- -(-15[ns])
0
1
DZB
On/on
- (-8[ns])
1
0
DZC
On or off
Close to 0 (0[ns])
1
1
DZD
Off/off
+ (+8[ns])
Notes
Illegal setting
(3) Dead zone mode characteristics and selection criteria
This section describes the characteristics of each dead zone mode and the criteria for selecting that mode.
(1) DZA mode
In DZA mode, the correction signal is output from the charge pump even if the reference frequency (fr) and
comparison frequency (fp) match. This results in excellent signal-to-noise ratio characteristics. However, due to
the generation of reference frequency component sidebands, beating may occur in the presence of a strong input
signal. This is because the PLL loop responds sensitively to leakage components from the RF stage through the
mixer and this modulates the VCO.
(2) DZB mode
Like DZA mode, in DZB mode the correction signal is output from the charge pump even if the reference
frequency (fr) and comparison frequency (fp) match. However, the correction signal voltage is lower in DZB
mode than in DZA mode. The feature of this mode is that it provides a better signal-to-noise ratio than DZC or
DZD mode yet is less susceptible to beating than DZA mode.
(3) DZC mode
In DZC mode, a correction signal proportional to the phase difference between the reference frequency (fr) and
comparison frequency (fp) is output from the charge pump. A small amount of noise may occur when the phase
difference is close to 0 ns. Since the signal-to-noise ratio may degrade significantly at low temperatures (under
-30°C), this mode should not be used.
(4) DZD mode
In DZD mode, a correction signal proportional to the phase difference between the reference frequency (fr) and
comparison frequency (fp) is output from the charge pump. The correction signal is not output when the phase
difference is in the vicinity of ± <a few ns>. As a result the signal-to-noise ratio is worse than the other modes, but
the occurrence of beating is suppressed.
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