TDA7529 datasheet(13/60 Pages) STMICROELECTRONICS

13 / 60 page

TDA7529

Function description

13/60

Figure 4.

Positive/negative current diagram

Constant current mode: the output current can be set to 2 mA source current. The AGC

detector is in power -down mode and only the PIN diode driver is active.

Voltage and current mode with hand-over: the Vthr level is programmable with 6 bit in

the range of 0.2V to 2.56V. The voltage Vthr is the internal reference voltage of an

external cascode transistor emitter feedback loop.

Figure 5.

Voltage and current mode with hand-over

The voltage output swing is comprised between 0V and 3.3V (VDD).

The microcontroller can read the voltage at the AGC capacitor via the serial control

interface.

3.3

AM RF-AGC

The AM AGC system is controlled by an average detector. The time constant of the AM RF-

AGC is defined by an external capacitor connected to TCAM and programmable internal

currents with symmetrical attack/decay behavior.

The AM RF-AGC has two output pins to drive one PIN diode attenuator and the external

preamplifier gain control.

The AGC outputs can be programmed to the same modes as the FM RF-AGC with the

exception of pos/neg current.

The microcontroller can read the voltage at the AGC capacitor via the serial control

interface.

1.65V

Iout

15mA

f(e) current

AC00041

Iout

Vout

Vthr

AC00042

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