4.3.1 Bridge voltage monitor
This signal monitors the voltage provided to the H-bridge either by DC-DC boost or directly by VIN in case of DC-
DC bypass. The value is available in the GUI.
4.3.2 DC-DC current monitor
This signal monitors the current to the DC-DC buck/boost. It is measured on sensing resistor and is used for DC-
DC regulation and overcurrent protection. The value is not available in the GUI.
4.3.3 Bridge current monitor
This signal monitors current going through the main H-bridge. Measured on a high-precision sensing resistor. The
signal is used for many purposes including ASK demodulation, FOD, and current limitation. The mean value is
available in the GUI.
An external low-pass filter is used to filter the current monitor signal.
4.3.4 Ring voltage monitor
This signal monitors the voltage in the node between C
TANK
and the transmitter's coil pin. The signal is used for
many purposes, including OVP, FOD, and Q factor measurement.
The value is not available in the GUI.
The ring voltage is AC coupled with STWBC2 using an RC circuit. As the RNG_SNS pin is maintained at a fixed
voltage, the ring voltage is converted to current flowing into the RNG_SNS pin thanks to the resistor.
4.4 Onboard voltage sources
STWBC2 features several LDOs and level shifters, which are used to supply the internal circuitry of the device. As
an example, the 3.3 V power supply is used to power the MCU, while the 1.8 V LDO is used to power the AFE.
4.4.1 DC-DC buck converter
The DC-DC buck converter can work in two modes: a 5 V output voltage (for VIN > 5.5 V) or a 3.6 V output
voltage.
The maximum output current is 450 mA, including both user application and the consumption of the STEVAL-
WBC2TX70 itself.
The buck converter is supplied from the VIN pin of STWBC2, and its output is used to power the internal circuitry
(VDD). The buck output voltage can also be used to power user applications.
4.4.2 The 3.3 V LDO
The 3.3 V output is generated from VDD. The 3.3 V is used to power the MCU, analog low-voltage circuits, and
level shifters of STWBC2. The maximum output current is 150 mA (user application + STEVAL-WBC2TX70
consumption). External LDO capacitors should be placed as close to the IC as possible.
4.4.3 The 1.8 V LDO
The 1.8 V output is generated from VDD. The 1.8 V is used to power the AFE digital core of STWBC2 and the
level shifters. The maximum output current is 50 mA (user application + STEVAL-WBC2TX70 consumption).
External LDO capacitors should be placed as close to the IC as possible.
4.4.4 Voltage Doubler
The voltage doubler is used to generate voltage higher than the 5 V, required by the gate drivers and the higher
voltage IOs (LED/buzzer driver). The doubler voltage is generated from the DC-DC buck voltage, and the output
is given by the voltage provided: a 3.6 V DC-DC buck voltage results in 6.5 V, while a 5 V input results in a 9.2 V
output. The maximum output current is 25 mA.
UM3286
Device description and operation
UM3286 - Rev 1
page 9/84
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