11274-001 AMI Semiconductor, Inc., 11274-001 Datasheet - Page 5

• Manufacturer Part Number: 11274-001
• Description: Logic and Timing, Programmable Line Lock Clock Generator IC, Tape and Reel
• Manufacturer: AMI Semiconductor, Inc.

To enter this mode, set STAT[1] to one and clear
STAT[0] to zero. If the CMOS bit is set to one, the
LOCK/IPRG pin can display the flag. The flag is always
available under software control by reading back the
STAT[1] bit, which will be overwritten by the flag in this
mode.
4.2.4
The Feedback Divider clock can be brought out the
LOCK/IPRG pin independent of the output clock to allow
monitoring of the Feedback Divider clock. To enter this
mode, set both the STAT[1] and STAT[0] bits to one. The
CMOS bit must also be set to one to enable the
LOCK/IPRG pin as an output.
4.3
For applications where an external loop filter is required,
the following analysis example can be used to determine
loop gain and stability.
The loop gain of a PLL is the product of all of the gains
within the loop.
Establish the basic operating parameters:
Set the charge pump current:
Set the loop filter values:
Set the VCO gain (VCOSPD):
Set the Feedback Divider:
Set the Reference frequency (at the input to the Phase
Detector:
The transfer function of the Phase Detector and Charge
Pump combination is (in A/rad):
The transfer function of the loop filter is (in V/A):
Loop Gain Analysis
Feedback Divider Monitoring
K
LF
(
s
)
K
sC
PD
2
æ
ç
ç
ç
ç
è
I
R
chgpump
2
LF
C
C
I
R
A
N
f
1
chgpump
1
VCO
REF
LF
2
F
æ
ç
è
1
. 0
220
1
3500
15
sC
015
20
230
k
10
1
pF
kHz
ö
÷
ø
MHz
ö
÷
÷
÷
÷
ø
F
A
/
V
5
The VCO transfer function (in rad/s, and accounting for
the phase integration that occurs in the VCO) is:
The transfer function of the Feedback Divider is:
Finally, the sampling effect that occurs in the Phase De-
tector is accounted for by:
The loop gain of the PLL is:
Figure 8: Loop Gain vs. Frequency
Programmable Line Lock Clock Generator IC
Programmable Line Lock Clock Generator IC
Programmable Line Lock Clock Generator IC
Programmable Line Lock Clock Generator IC
0.01
100
0.1
10
0.1kHz
K
1
LOOP
(
K
s
)
SAMP
K
K
(
VCO
s
PD
1kHz
)
K
K
(
Frequency (f
s
LF
æ
ç
ç
ç
è
F
)
1
(
s
)
2
e
N
K
1
FS6131-01
FS6131-01
FS6131-01
FS6131-01
s
æ
ç
è
VCO
A
F
s
VCO
i
f
)
REF
10kHz
(
s
1
s
ö
÷
ø
)
K
ö
÷
÷
÷
ø
f
F
REF
K
SAMP
(
s
100kHz
)