Philips Semiconductors
Product specification
1GHz low-voltage Fractional-N synthesizer
SA7025
REFERENCE R
MAIN N
TIME
VCO CYCLES
N
N
N + 1
N
N + 1
DETECTOR
OUTPUT
2
4
1
3
0
CONTENTS
ACCUM.
FRACTIONAL
COMPENSATION
CURRENT
PULSE-WIDTH
MODULATION
mA
OUTPUT ON
PHP, PHI
µA
PULSE-LEVEL
MODULATION
SR00608
Figure 9. Waveforms for NF = 2, Fraction = 0.4
PA registers. The f
of the Auxiliary divider.
signal can be used to verify the divide ratio
Lock Detect
AUX
The output LOCK is H when the auxiliary phase detector AND the
main phase detector indicates a lock condition. The lock condition
is defined as a phase difference of less than +1 cycle on the
reference input REF_IN. The lock condition is also fulfilled when the
relative counter is disabled (EM = “0” or respectively EA = “0”) for
the main, respectively auxiliary counter.
If T1 = High and T0 = High, the lock output is configured as f
The signal is the buffered output of the MAIN divider. The f
signal appears as normally high and pulses low whenever the
divider reaches terminal count from the value programmed into the
NM1, NM2 or NM3 registers. The f signal can be used to verify
.
MAIN
MAIN
MAIN
the divide ratio of the MAIN divider and the prescaler.
Test Modes
The lock output is selectable as f
, f
, f
and lock. Bits T1
REF AUX MAIN
and T0 of the E word control the selection (see Figures 6 and 10).
If T1 = T0 = Low, or if the E-word is not sent, the lock output is
configured as the normal lock output described in the Lock Detect
section.
If T1 = Low and T0 = High, the lock output is configured as f
.
REF
The signal is the buffered output of the reference divider NR and the
3-bit binary counter SM. The f signal appears as normally low
REF
and pulses high whenever the divider reaches terminal count from
the value programmed into the NR and SM registers. The f
REF
signal can be used to verify the divide ratio of the Reference divider.
If T1 = High and T0 = Low, the lock output is configured as f
.
AUX
The signal is normally high and pulses low whenever the divider
reaches terminal count from the value programmed into the NA and
14
1996 Aug 6
NXP [ NXP ]
