RFM95 Datasheet, PDF (80/121 Pages) List of Unclassifed Manufacturers – Low Power Long Range Transceiver Module

WIRELESS & SENSING
RFM95/96/97/98(W)
PRELIMINARY
DATASHEET
5.4.4. Over Current Protection
The power amplifiers of RFM95/96/97/98(W) are protected against current over supply in adverse RF load conditions by
the over current protection block. This has the added benefit of protecting battery chemistries with limited peak current
capability and minimising worst case PA consumption in battery life calculation. The current limiter value is controlled by the
OcpTrim bits in RegOcp, and is calculated according to the following formulae:
Table 81 Trimming of the OCP Current
OcpTrim
0 to 15
16 to 27
27+
I_MAX
45 to 120 mA
130 to 240 mA
240 mA
Imax Formula
45 + 5*OcpTrim [mA]
-30 + 10*OcpTrim [mA]
240 mA
Note Imax sets a limit on the current drain of the Power Amplifier only, hence the maximum current drain of the RFM96/
77/78 is equal to Imax + I_FS.
5.5. Receiver Description
5.5.1. Overview
The RFM95/96/97/98(W) features a digital receiver with the analog to digital conversion process being performed directly
following the LNA-Mixers block. In addition to the LoRa^TM modulation scheme the low-IF receiver is able to demodulate
ASK, OOK, (G)FSK and (G)MSK modulation. All filtering, demodulation, gain control, synchronization and packet handling
is performed digitally allowing a high degree of programmable flexibility. The receiver also has automatic gain calibration,
this improves the precision of RSSI measurement and enhances image rejection.
5.5.2. Receiver Enabled and Receiver Active States
In the receiver operating mode two states of functionality are defined. Upon initial transition to receiver operating mode the
receiver is in the ‘receiver-enabled’ state. In this state the receiver awaits for either the user defined valid preamble or RSSI
detection criterion to be fulfilled. Once met the receiver enters ‘receiver-active’ state. In this second state the received
signal is processed by the packet engine and top level sequencer. For a complete description of the digital functions of the
RFM95/96/97/98(W) receiver please see Section 4 of the datasheet.
5.5.3. Automatic Gain Control In FSK/OOK Mode
The AGC feature allows receiver to handle a wide Rx input dynamic range from the sensitivity level up to maximum input
level of 0dBm or more, whilst optimizing the system linearity.
The following table shows typical NF and IIP3 performances for the RFM95/96/97/98(W) LNA gains
available.
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