TDA5150 Datasheet, PDF (49/106 Pages) Infineon Technologies AG – On-chip, high resolution fractional-N synthesizer and Sigma-Delta modulator with ASK, FSK, GFSK options

TDA 5150
TDA 5150 Functional Description
2.4.8.5 Fail-Safe PA Switch Off
To prevent erroneous transmissions (on wrong frequency or with erroneous modulation
parameters, altered payload etc.) the activation of Fail-Safe mechanism is coupled with
deactivation (switching off) of the RF Power Amplifier stages. If critical errors occur, the
Fail-Safe mechanism incorporated in the TDA5150 is activated, provided the detection
enable bit is armed (i.e. bit FSOFF in SFR TXCFG0 (0x04.4) is 0).
Observe that this corresponds to the after-reset state. In other words, by exiting the reset
state, the Fail-Safe detection is already armed, but it can be deactivated anytime by
changing its control bit state to High (bit FSOFF=1 (0x04.4)) or rearmed, by setting it to
Low.
If the detection is armed, RF Power Amplifier drivers are automatically switched OFF in
case of an error, to prevent erroneous transmissions.
This happens if at least one of the following events occurs:
• Parity error in the SFRs
• Brownout event (event sensed by the brown-out detector BOD)
• PLL lock failure is detected (event sensed by the lock detector LD)
If the detection is disabled, the error flags in Transmitter Status Register (0x01) still keep
track of error status (i.e. they are set, if an error occurs) but the RF Power Amplifier is
not switched off by the error flag(s) set condition (i.e. the RF-PA continues to transmit
despite error until the transmission is terminated as a normal, error-free one).
Refer to Transmitter Status Register (0x01) description and Fail-Safe Flags, explained
in next Chapter 2.4.8.6 SFRs related to RF Power Amplifier and ASK Modulator.
Data Sheet
49
V 1.0, July 2009