參數(shù)資料
型號(hào): CD74HC7046
廠商: Texas Instruments, Inc.
英文描述: Phase-Locked Loop with VCO and Lock Detector
中文描述: 鎖相環(huán)與VCO和鎖定檢測(cè)回路
文件頁數(shù): 21/26頁
文件大?。?/td> 302K
代理商: CD74HC7046
21
Lock Detector Circuit
The lock detector feature is very useful in data synchroniza-
tion, motor speed control, and demodulation. By adjusting
the value of the lock detector capacitor so that the lock out-
put will change slightly before actually losing lock, the
designer can create an “early warning” indication allowing
corrective measures to be implemented. The reverse is also
true, especially with motor speed controls, generators, and
clutches that must be set up before actual lock occurs or dis-
connected during loss of lock.
When using phase comparator 1, the detector will only indi-
cate a lock condition on the fundamental frequency and not
on the harmonics, which PC1 will lock on.
PLL Conditions with
No Signal at the
SIG
IN
Input
PC1
VCO adjusts to f
o
with
φ
DEMOUT
= 90
o
and V
VCOIN
= 1/2 V
CC
(see Figure 2)
VCO adjusts to f
MIN
with
φ
DEMOUT
= -360
o
and V
VCOIN
= 0V (see Figure 4)
PC2
PLL Frequency
Capture Range
PC1 or PC2
Loop Filter Component Selection
PLL Locks on
Harmonics at Center
Frequency
PC1
Yes
PC2
No
Noise Rejection at
Signal Input
PC1
High
PC2
Low
f
r
= 2f
i
, large ripple content at
φ
DEMOUT
= 90
o
f
r
= f
i
, small ripple content at
φ
DEMOUT
= 0
o
AC Ripple Content
when PLL is Locked
PC1
PC2
SUBJECT
PHASE
COMPARATOR
DESIGN CONSIDERATIONS
A small capture range (2f
c
) is obtained if
τ
> 2f
c
(1/
π
)
(2
π
f
L
/
τ
1
.)
1/2
FIGURE 48. SIMPLE LOOP FILTER FOR PLL WITHOUT OFFSET
(A)
τ
1 = R3 x C2
(B) AMPLITUDE CHARACTERISTIC
(C) POLE-ZERO DIAGRAM
R3
C2
INPUT
OUTPUT
|F
(j
ω
)
|
ω
-1/
τ
FIGURE 49. SIMPLE LOOP FILTER FOR PLL WITH OFFSET
(A)
τ
2 = R4 x C2;
τ
3 = (R3 + R4) x C2
(B) AMPLITUDE CHARACTERISTIC
(C) POLE-ZERO DIAGRAM
|F
(j
ω
)
|
ω
-1/
τ
2
R3
C2
INPUT
OUTPUT
-1/
τ
3
m
1/
τ
3
1/
τ
2
R4
m =
R4
R3 + R4
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CD74HC7046A 制造商:Texas Instruments 功能描述:
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CD74HC7046AE WAF 制造商:Harris Corporation 功能描述: 制造商:Texas Instruments 功能描述:
CD74HC7046AE 制造商:Texas Instruments 功能描述:PLL Logic IC 制造商:Texas Instruments 功能描述:IC, PLL WITH VCO, 18MHZ, 16-DIP
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