ata5780 ATMEL Corporation, ata5780 Datasheet - Page 17

• Manufacturer Part Number: ata5780
• Description: Uhf Ask/fsk Receiver
• Manufacturer: ATMEL Corporation

4.3.3
4.3.3.1
4.3.3.2
4.3.4
4.4
4.4.1
9207BS–RKE–01/11
SPDT Block
Transparent RX Mode
RSSI
Receiver Damping
TMDO / TMDO_CLK
TRPA / TRPB
The received data stream and a corresponding data clock are available on pin 17 (TMDO) and
19 (TMDO_CLK) if the following conditions are fulfilled,
If the demodulator path A and path B are enabled, the first path to get a successful bit check or
valid start bit/SFID is passed through to pin TMDO (pin17) and pin TMDO_CLK (pin 19).
This transparent signal is a raw signal directly from the demodulator output.
An RSSI buffer is provided to analyze the signal strength profile based on the telegram length.
The RSSI buffer length is 32 bytes. The RSSI sample rate can be programmed to be between
250µs and 4ms. The RSSI buffer is organized as a ring-buffer and the customer must ensure
there is buffer overflow. RSSI sampling is started with the start bit/SFID okay. When starting
RX mode or when the ID check fails during polling, the RSSI buffer pointer is set to the initial
values (reset).
This feature allows a desired signal to be received in the presence of strong blockers. If the
damping is activated, the reception path has 15dB more attenuation. This damping can be set
by a control register bit located in the front-end register. An RF detector is implemented in the
LNA circuitry which detects overload power in the LNA stage. This condition can be read out
via an SPI command. This detector is activated during PLL start and based on this result the
damping switches are set. Because the damping in this case is located in the front of the LNA,
overloading can be reduced.
Of course this overload protection of 15dB leads to a sensitivity loss of 15dB, but it still
enables data reception in the presence of modulated blockers 15dB above the 1dB compres-
sion point (ICP1dB = –35dBm).
• RX transparent mode is enabled
• Successful bitcheck/wake-up check
• Valid startbit/SFID
Atmel ATA5780 [Preliminary]
17