SA9025 データシートの表示（PDF） - Philips Electronics
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SA9025 Datasheet PDF : 23 Pages
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Philips Semiconductors
900 MHz transmit modulator and 2.2 GHz
fractional–N synthesizer
Objective specification
SA9025
REFERENCE
INPUT
DIVIDE BY NREF
/2
/2 /2
MAIN SELECT
RSM = “00”
RSM = “01”
RSM = “10”
RSM = “11”
RSA = “11”
RSA = “10”
RSA = “01”
RSA = “00”
AUXILIARY SELECT
Figure 8. Reference Variable Divider
SR01440
Phase Detectors (Figure 9)
The auxiliary and main phase detectors each consist of a 2 D-type
flip-flop phase and frequency detector. Each flip-flop is set by the
negative edge of the divider terminal count output pulse. The reset
inputs are activated after a delay when both flip-flops have been set.
This avoids non-linearity or dead-band around zero phase error.
The flip-flops drive on-chip charge pumps. A pull-up current from
the charge pump indicates the VCO frequency shall be increased
while a pull-down pulse indicates the VCO frequency shall be
decreased.
Current Settings
The IC has two current setting pins, RN and IPEAK. The active
charge pump currents and the fractional compensation currents are
linearly dependent on the current in the current setting pins. This
current, ISET, is set by an external resistor connected between the
current setting pin and VSS.
Auxiliary Output Charge Pumps
The auxiliary charge pumps on pin PHA are driven by the auxiliary
phase detector and the current value is determined by the external
resistor attached to pin RN.
1997 Aug 01
18
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