ACE9030
Typical performance for noise power measured in the
adjacent channels,16 kHz wide at 25 kHz offset is – 70 dBc.
To power down the multiplier if it is not required, a Normal
command can be used with DATA3 bit D6 set to LOW, to set
the multiplier power on DATA3 bit D6 should be set to HIGH:
DAC2
DAC2
CIN1
47 pF
DATA1
xxxxxxxx
DATA2
01xxxxxx
DATA3
x D6 xxxxxx
C1
82 pF
1 nF
CIN2
D1
BB535
D2
BB639
C2
Band-Gap Reference
82 pF
A band-gap voltage reference is used to set levels in the
ADC, in the DAC’s and the currents in the synthesiser charge
pumps. This voltage is smoothed by an external decoupling
capacitor on the DECOUP pin.
The voltage derived for the ADC full range reference can
be monitored through pin DOUT8. The Radio Interface DAC
reference is nominally the same as the ADC reference and it
can be monitored independantly of DOUT8 by setting DAC3
(the low output impedance DAC) to full scale.
To power down the band-gap reference to allow the use
ofanexternalreferencevoltageonpinDECOUPthefollowing
Set-up command can be used:
Fig. 14 Crystal Oscillator Trimming Circuit with Typical
Component Values
Crystal Multiplier for LO2
To mix the first intermediate frequency signal down to the
second IF a second local oscillator is needed. In the ACE9030
thereisacrystalfrequencymultipliertogeneratethissignalby
squaring the crystal oscillator waveform and selecting the
desired harmonic. To multiply the crystal frequency by 3 or 5
outputLO2isdrivenatthereferencefrequencywitha1:1mark
space ratio. This ratio of 1:1 is chosen to minimise the even
harmonics, especially the second and fourth. A tuned circuit
will pick off the required harmonic. ACE9030 is specified with
theexternalcomponentsshowninFigure15giving44.55MHz
derivedfrom14.85MHzcrystal. The6.8kΩ resistorand5.6pF
capacitor represent the input impedance of a typical IF
amplifier LO input.
DATA1
DATA2
DATA3
xxxxxxxx
10 xxxxxx
x D6 xxxx00
where the band-gap is powered down if DATA3 bit D6 is LOW
or is active if DATA3 bit D6 is HIGH.
The band-gap voltage multiplier for the ADC and DAC
reference (nominally 3·45 V) can be adjusted by a Set-up
command to correct for production spreads:
TUNED CIRCUIT AT
HARMONIC, VALUES
DATA1
DATA2
DATA3
GIVEN FOR 44.55 MHz
VDDA
DDDDDDDD
10xxxxxx
xxx1xx00
ACE9030
47 pF
220 nH
470
where the value in DATA1, GBG, sets the gain from band-gap
to output voltage according to the approximate equation:
MIXER
LOAD
DRIVE
FROM
LO2
CRYSTAL
OSC.
3
100 pF
BG
V
OUT
BG
(430 x G + 355 x 10 )
(145 x 103)
6 k8
5.6 pF
=
V
VSSA
For a typical VBG of 1·2 V the number is approximately 144
(= 90HEX) and for a typical VBG of 1·3 V the number is approxi-
mately 70 (= 46HEX) and a suitable trimming pattern can be
chosen.
Fig. 15 Basic Circuit of the Crystal Multiplier
Typical frequencies generated by the multiplier are:
Crystal Multiplier
LO2
1st I.F.
2nd I.F.
14·85 MHz
15·36 MHz
x 3
x 5
44·55 MHz 45·00 MHz 450 kHz
76·80 MHz 77·25 MHz 450 kHz
18
MITEL [ MITEL NETWORKS CORPORATION ]
