LV25400W Sanyo Semicon Device, LV25400W Datasheet - Page 37

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

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Phase Comparator and Charge Pump Circuits
(1) Phase comparator and charge pump operation
In the PLL circuit block shown in figure 1, the phase comparator compares the phases of the reference frequency (fr)
and the comparison frequency (fp), and outputs the amount of the phase difference from the charge pump.
Figure 2 shows the phase comparator/charge pump output characteristics. The phase comparator outputs a voltage Vφ
that is proportional to the phase difference φ between fr and fp. The phase comparator's characteristics can be
switched by changing the phase comparator dead zone mode setting. The phase comparator can be set to modes (DZA,
DZB) in which both the charge pump p-channel and n-channel sides are turned on when the phase difference is small,
or can be set to a mode (DZD) that does not output the phase difference when the phase difference is small.
fr > fp
fr > fp
D ZA
mode
D ZC
mode
Programmable Divider
Reference Divider
Figure 2 Phase Comparator/Charge Pump Characteristics
Vφ[V]
Vφ[V]
Dead Zone ≈ 0
Dead Zone(--)
fp > fr
φ err[ns]
φ err[ns]
Figure 1 PLL Circuit Block
fp > fr
fp
fr
Detector
LV25400W
Phase
Charge
Pump
fr > fp
fr > fp
D ZB
mode
D ZD
mode
RF
Leakage during
strong-field input
LPF
Vφ[V]
Vφ[V]
Dead Zone(-)
Dead Zone(+)
Mixer
VCO
fp > fr
φ err[ns]
φ err[ns]
fp > fr
No.A0633-37/42
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