TLC2933A

HIGH PERFORMANCE PHASE LOCKED LOOP

SLES149 − OCTOBER 2005

4

TI.COM

FIN−A

FIN−B

PFD OUT

VOH

HI-Z

VOL

Figure 2. PFD Function Timing Chart

PFD inhibit control

A high level on the PFD INHIBIT terminal places PFD OUT in the high-impedance state and the PFD stops

phase detection as shown in Table 3. A high level on the PFD INHIBIT terminal can also be used as the

power-down mode for the PFD.

Table 3. VCO Output Control Function

PFD INHIBIT

DETECTION

PFD OUT

IDD(PFD)

Low

Active

Active

Normal

High

Stopped

Hi−Z

Power Down

VCO block schematic

PFD block schematic

FIN−A

FIN−B

PFD INHIBIT

PFD OUT

VDD

Charge Pump

Detector