ZHCS363L August 2011 – March 2017 TRF7970A
PRODUCTION DATA.
The TRF7970A positive supply input VIN (pin 2) sources three internal regulators with output voltages VDD_RF, VDD_A and VDD_X. All regulators use external bypass capacitors for supply noise filtering and must be connected as indicated in reference schematics. These regulators provide a high power supply reject ratio (PSRR) as required for RFID reader systems. All regulators are supplied by VIN (pin 2).
The regulators are not independent and have common control bits in register 0x0B for output voltage setting. The regulators can be configured to operate in either automatic or manual mode (register 0x0B, bit 7). The automatic regulator setting mode ensures an optimal compromise between PSRR and the highest possible supply voltage for RF output (to ensure maximum RF power output). The manual mode allows the user to manually configure the regulator settings. For applications in which the TRF7970A may be subjected to external noise, manually reducing the regulator settings can improve RF performance.