SA8028 Ver la hoja de datos (PDF) - Philips Electronics
Número de pieza
componentes Descripción
Fabricante
SA8028
Philips Electronics
SA8028 Datasheet PDF : 28 Pages
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Philips Semiconductors
2.5 GHz sigma delta fractional-N /
760 MHz IF integer frequency synthesizers
Product data
SA8028
1.4 Phase detector (see Figure 6)
The reference signal and the RF (IF) divider output are connected to a phase frequency detector that controls the charge pumps. The dead
zone (caused by the finite time taken to switch the charge pump current sources on or off) is cancelled by forcing the pumps ON for a minimum
time (backlash time, τ) at every cycle providing improved linearity.
VDDCP
“1”
D
Q
fREF
* see note
CLK
R
R
P
P–TYPE
CHARGE PUMP
τ
IPH
IF/RF
DIVIDER
“1”
D
R
CLK
X
Q
N–TYPE
N
CHARGE PUMP
GNDCP
fREF
R
X
τ
P
τ
N
IPH
SR02413
NOTES:
For the RF synthesizer, the output of the reference input buffer is routed directly (not divided) to the input of the RF phase detector. Whereas
for the IF synthesizer, the reference input to the IF phase detector is the output from the reference divider.
τ (backlash time) is the delay that fixes the minimum allowable charge pump activity time.
Figure 6. Phase detector structure with timing.
2002 Feb 22
9
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