2 Use of the evaluation kit in passive mode
Passive mode means that NAC1080 IC does not require any external wired connected power supply and the
energy needed to supply the IC can be harvested wirelessly from the NFC field generated by the NFC reader.
Part of the harvested energy can be stored in the dedicated storage capacitor (C7 or C10) located on the board
to enable operations with the mini motor needed for the smart lock system. The evaluation board supports
testing and development of dierent methods to rotate the motor – simple one-step movement, one-step
movement with external boost-buck or multi-step method.
Table 1 shows the configuration of the board for dierent methods and gives a short description of
each method. For more detailed information about the methods see application note NFC passive lock
implementation with NAC1080. The installed firmware supports simple one-step and multi-step methods,
and switching between them is available via the mobile application soware. By default the firmware is
configured for simple one-step movement. To use one-step movement with the external boost-buck circuit
method ‒ other firmware (which is available on the Infineon webpage aer the evaluation board registration)
must be programmed and the jumper setting on the evaluation board needs to be changed as detailed in Table
1.
Table 1 Configuration of the evaluation board for dierent methods of motor rotation
Method name Simple one-step
movement
One-step movement
with external boost-
buck circuit
Multi-step movement
Method
description
One-step motor
movement. Energy
required to rotate the
motor is stored in
an external energy
storage capacitor
at once. Charge
the external energy
storage capacitor to
reach the voltage
clamping level first,
then discharge the
capacitor to rotate
the motor. Connect
an external energy
storage capacitor to
the IC VCC_HB output
pin to store the
harvested energy.
Voltage across the
capacitor is limited
by NAC1080 clamping
voltage: max. 3.6 V.
One-step motor
movement. Energy
required to rotate the
motor is stored in the
energy storage capacitor
at once. The working
principle is the same
as the “simple one-
step movement”, but
the voltage across the
energy storage capacitor
is increased. A sequence
of a boost and a buck
converter is required.
Voltage across the
energy storage capacitor
steps up to 15 V using a
discrete boost circuit. A
buck converter reduces
the voltage back to 3.3 V
to supply the H-bridge of
NAC1080.
Stepwise motor movement. Energy
required to rotate the motor is
permanently harvested during motor
movement. An energy storage capacitor is
still required because the motor usually
consumes more power than can be
harvested at a certain point of time.
This method controls the motor turn-on
and turn-o operating points with the
specified time interval or with the given
VCC_HB voltage threshold. Voltage across
the energy storage capacitor is limited
by NAC1080 clamping voltage: max 3.6
V. Implemented as a number of charging-
moving cycles. One cycle description: the
capacitor starts to charge when the NFC
energy harvesting is available and the
motor is switched o. Aer the capacitor
voltage reaches the required voltage level
(VON), the H-bridge turns on and the
motor starts to rotate. When the voltage
drops down to VOFF, the motor is switched
o. Such cycles are repeated until the
required rotation angle is reached.
(table continues...)
User manual for NAC1080 development
2 Use of the evaluation kit in passive mode
User Manual 3 V1.0
2022-06-23
