TLC2933IPWR datasheet(15/21 Pages) TI

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TLC2933

HIGH-PERFORMANCE PHASE-LOCKED LOOP

SLAS136A – APRIL 1996 – REVISED JUNE 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATION INFORMATION

Using the lag-lead filter in Figure 17(b) and divider N value, the transfer function for phase and frequency are

shown in equations 4 and 5. Note that the transfer function for phase differs from the transfer function for

frequency by only the divider N value. The difference arises from the fact that the feedback for phase is unity

while the feedback for frequency is 1/N.

Hence, the transfer function of Figure 17(a) for phase is

F2(s)

F1(s) +

@ KV

@ (T1 ) T2)

) s

@ T2

) s 1 )

@KV @T2

@(T1)T2)

)

@(T1)T2)

(4)

and the transfer function for frequency is

OUT(s)

REF(s)

@ KV

(T1

) T2)

) s

@ T2

) s

@ 1 )

@T2

@(T1)T2)

)

@KV

@(T1)T2)

(5)

The standard 2-pole denominator is D = s2 + 2

ζ ωn s + ωn2 and comparing the coefficients of the denominator

of equation (4) and (5) with the standard 2-pole denominator gives the following results.

wn +

@ KV

@ (T1 ) T2)

Solving for T1 + T2

) T2 +

@ KV

@ w 2

(6)

and by using this value for T1 + T2 in equation (6) the damping factor is

z +

2 @

)

@ K

solving for T2

w –

@ K

then by substituting for T2 in equation (6)

@ Kp

@ w 2

–

)

@ K

(7)

(8)

(9)

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