ACE9030MSLASHIWSLASHFP2N datasheet(18/39 Pages) MITEL

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ACE9030

DAC2

CIN1

CIN2

1 nF

47 pF

82 pF

BB639

BB535

VSSA

47 pF

100 pF

LO2

470

MIXER

LOAD

6 k8

TUNED CIRCUIT AT

HARMONIC, VALUES

GIVEN FOR 44.55 MHz

VDDA

ACE9030

220 nH

DRIVE

FROM

CRYSTAL

OSC.

5.6 pF

Crystal

Multiplier

LO2

1st I.F.

2nd I.F.

14·85 MHz

x 3

44·55 MHz 45·00 MHz 450 kHz

15·36 MHz

x 5

76·80 MHz 77·25 MHz 450 kHz

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

there is a crystal frequency multiplier to generate this signal by

squaring the crystal oscillator waveform and selecting the

desired harmonic. To multiply the crystal frequency by 3 or 5

output LO2 is driven at the reference frequency with a 1:1 mark

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

the external components shown in Figure 15 giving 44.55 MHz

derived from 14.85 MHz crystal. The 6.8k

Ω resistor and 5.6pF

capacitor represent the input impedance of a typical IF

amplifier LO input.

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:

Typical frequencies generated by the multiplier are:

Fig. 15 Basic Circuit of the Crystal Multiplier

Band-Gap Reference

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

of an external reference voltage on pin DECOUP the following

Set-up command can be used:

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:

DATA1

DATA2

DATA3

DDDDDDDD

10xxxxxx

xxx1xx00

DATA1

DATA2

DATA3

xxxxxxxx

10 xxxxxx

x D

6 xxxx00

DATA1

DATA2

DATA3

xxxxxxxx

01xxxxxx

x D

6 xxxxxx

where the value in DATA1, G

BG, sets the gain from band-gap

to output voltage according to the approximate equation:

For a typical V

BG of 1·2 V the number is approximately 144

(= 90

HEX) and for a typical VBG of 1·3 V the number is approxi-

mately 70 (= 46

HEX) and a suitable trimming pattern can be

chosen.

OUT

(430 x G

+ 355 x 103)

(145 x 103)

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