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Application note
COMPANY PUBLIC
Rev. 1.1 — 19 June 2018
345311
4.4.3 Tx envelope shape
The PN5180 provides some registers to adjust the wave shapes. The following
description is a generic description. A more detailed description can be found in [14] and
[15], since it is mainly related to the DPC antenna tuning.
4.4.4 TX_CLK_MODE
For type A the 100% ASK is enabled, so basically no residual carrier needs to be
adjusted. However, the TX_CLK_MODE_RM (RF_CONTROL_TX_CLK register) allows
to change the TX output stage behavior during the modulation pulses. The Fig 41 shows
an example with the default setting as well as the setting, where the TX output stages are
open drain, and only the low side MOS (pull) are actively driven. The green signal shows
the field, picked up with the ReferencePICC in a few cm distances. The yellow signal
shows the TX output using a standard probe with a standard GND cable. These signals
just indicate the difference between different register settings in principle.
a. TX_CLK_MODE_RM = 001bin (Default)
b. TX_CLK_MODE_RM = 101bin (low side pull)
The RF_CONTROL_TX, the TX_UNDERSHOOT_CONFIG and the
TX_OVERSHOOT_CONFIG in combination with the RF_CONTROL_TX_CLK allow to
adjust the shape of the falling and rising edges of the Tx envelope signal (see the
principle in Fig 42).
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