LV25400W Datasheet, PDF (37/42 Pages) Sanyo Semicon Device – Bi-CMOS LSI DSP Tuner Front End for Automotive Applications

LV25400W
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 1 PLL Circuit Block
fr
Reference Divider
fp
Programmable Divider
Phase
Detector
Charge
Pump
RF
Mixer
Leakage during
strong-field input
LPF
VCO
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.
Figure 2 Phase Comparator/Charge Pump Characteristics
D ZA
mode
Vφ[V]
fp > fr
fr > fp
φ err[ns]
Dead Zone(--)
D ZB
mode
Vφ[V]
fp > fr
fr > fp
φ err[ns]
Dead Zone(-)
D ZC
mode
Vφ[V]
fp > fr
fr > fp
φ err[ns]
Dead Zone ≈ 0
D ZD
mode
Vφ[V]
fp > fr
fr > fp
φ err[ns]
Dead Zone(+)
No.A0633-37/42