TLC2942 Datasheet, PDF (5/28 Pages) Texas Instruments – HIGH-PERFORMANCE DUAL PHASE-LOCKED LOOP BUILDING BLOCK

TLC2942
HIGH-PERFORMANCE DUAL PHASE-LOCKED LOOP BUILDING BLOCK
SLAS146B – NOVEMBER 1996 – REVISED JUNE 1997
VCO inhibit function
Each VCO has an externally controlled inhibit function that inhibits the VCO output. The VCO oscillation is
stopped during a high level on VCOINHIBIT, so the high level can also be used as the power-down mode. The
VCO output maintains a low level during the power-down mode (see Table 2 and Table 3).
VCOINHIBIT1
Low
High
Table 2. VCO1 Inhibit Function
VCO1 OSCILLATOR
Active
Stop
VCO OUT1
Active
Low
VCO1 IDD
Normal
Power Down
Table 3. VCO2 Inhibit Function
VCOINHIBIT2
Low
High
VCO2 OSCILLATOR
Active
Stop
VCO OUT2
Active
Low
VCO2 IDD
Normal
Power Down
PFD operation
The PFD is a high-speed, edge-triggered detector with an internal charge pump. The PFD detects the phase
difference between two frequency inputs supplied to F_IN–A and F_IN–B as shown in Figure 2. Nominally the
reference is supplied to F_IN–A, and the frequency from the external counter output is fed to F_IN–B.
FIN– A1,
FIN– A2
FIN– B1,
FIN– B2
PFD OUT1,
PFD OUT2
VOH
Hi-Z
VOL
Figure 2. PFD Function Timing Chart
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