LV25400W Sanyo Semicon Device, LV25400W Datasheet - Page 38

• Manufacturer Part Number: LV25400W
• Description: DSP Tuner Front End
• Manufacturer: Sanyo Semicon Device

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(2) Dead zone mode characteristics
(3) Dead zone mode characteristics and selection criteria
The table below presents an overview of the characteristics in each of the dead zone modes.
This section describes the characteristics of each dead zone mode and the criteria for selecting that mode.
(1) DZA mode
(2) DZB mode
(3) DZC mode
(4) DZD mode
DZ1
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.
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.
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.
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.
0
0
1
1
Setting
DZ0
0
1
0
1
Dead zone mode
DZA
DZB
DZC
DZD
Charge pump (p/n-channel) state at 0 phase
LV25400W
difference
On or off
On/on
On/on
Off/off
Dead zone width (for
reference purposes)
Close to 0 (0[ns])
- -(-15[ns])
+ (+8[ns])
- (-8[ns])
Illegal setting
No.A0633-38/42
Notes
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