TDA7528

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Description (continued)

The mixer outputs have a single ended low impedance design to drive one or two IF filters

with different bandwidths. A switchable-gain IF amplifier, independent IF AGC and an

integrated anti-aliasing stage drive the IF A/D converter of the STA3005 backend.

Programmable RF AGCs to actuate adjustable preamplifier stages and two D/A converters

for tuning external filter stages complete the reception path.

Two fully integrated VCOs are included in the TDA7528, oscillating in a range around 3.7

GHz and 4.7 GHz respectively. The output signal of the selected VCO drives a

programmable divider generating the LO signal for the mixer stage. The PLL, integrated with

the exception of the loop filter, allows reception on all the above-mentioned frequencies,

swift frequency changes in the standard tuning steps of 50 kHz for FM, 9 or 10 kHz for LW

and MW and 5 kHz for SW. The smallest available tuning steps are 12.5 kHz for FM and 1

kHz for all AM bands.

The TDA7528 frontend is controlled by a serial command interface, switchable between SPI

and I2C protocol. The external reference clock source is typically 74.1 MHz and intended to

be generated within the STA3005 back-end. However, the TDA7528 also features its own

reference oscillator typically intended to use a crystal at 74.4 MHz.

All the necessary calibration steps can be carried out electronically during production. An

integrated temperature sensor facilitates the adaptation of various parameters during

operation, like IF gain or AGC threshold.