LUCW3000CCN AGERE [Agere Systems], LUCW3000CCN Datasheet - Page 17

• Manufacturer Part Number: LUCW3000CCN
• Description: W3000 PLL Dual-Band Frequency Synthesizer
• Manufacturer: AGERE [Agere Systems]

Advance Data Sheet
December 1999
PLL Lock-Detect Function
The W3000 provides a basic lock-detect function for fault finding or for system specification requirements.
Inside the W3000, the length of the up or down pulses applied to the loop filter is compared with a reference
clock period. If the current pulses are shorter than a reference clock period for 15 consecutive comparison
periods, the LD line is asserted. If a current pulse is detected that is longer than a reference clock period, the LD
line is unset.
The LD line gives a signal to indicate a PLL fault condition. It does not provide a true loop-locked output. For
example, in a GSM system with a reference clock of 13 MHz and a comparison frequency of 200 kHz, the
current pulses only have to be less than 1/65 of a cycle for 15 consecutive times for the LD line to be asserted.
This equates to ~0.4º of phase. In the worst case, if the phase stays inside this limit, moving from one extreme to
the other, the frequency will only be within 0.2%, i.e., 4 MHz on a 2 GHz VCO.
The LD output from the W3000 is a standard logic signal and requires no external comparison or R-C filters.
Typical Performance Characteristics
MAIN_IN and REF_IN are set to cause a small beat frequency at the phase detector input. This generates a
sawtooth signal at the charge pump output of known slope. The amplitude of the UHF source is decreased. The
sensitivity limit is reached when the slope of this waveform deviates from the calculated value. This is then
repeated for the reference source.
Lucent Technologies Inc.
SOURCE
UHF
50
Figure 8. MAIN_IN and REF_IN Sensitivity Test Circuit Diagram
442
6.8 pF
+V
DD
100 pF
0.047 µF
100 pF
+V
DDC
V
CPOUT
V
V
MAIN_IN
V
V
CURRENT
DDC
SS
SS
DD
DD
METER
1
2
1
2
10 MHz REF
W3000 PLL Dual-Band Frequency Synthesizer
LOCK DET
V
PWRDN
DDC
REF_IN
/2
RES
DAT
CLK
LAT
RREF = 18 k
0.01 µF
REFERENCE
SOURCE
50
µC
V
DDC
17