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STWBC-EP

Pins functional description

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5

Pins functional description

This section describes the functions related to the pins of the device.

5.1

Power supplies: VDD, VDDA, VSS, VSSA, VOUT

The digital portion of the STWBC-EP is powered using VDD and VSS (typically 4.5 V).

The analog portion of the STWBC-EP is powered using VDDA and VSSA (typically 4.5 V).

VDD and VDDA should be correctly filtered to allow the correct operation of the device.

The STWBC-EP generates its own internal power supply which needs a filter capacitor

of 1 μF on the VOUT pin.

5.2

DC/DC converter: DCDC_DRV, DCDC_DAC, CMP_OUT_V,

CS_CMP, DCDC_DAC_REF, DEMAGNET, VTARGET

The STWBC-EP is designed to drive a DC/DC boost converter placed in front of the half

bridge coil driver. The DC/DC power switch (external NMOS) is driven by the DCDC_DRV

pin through an output buffer.

The DC/DC inductor charging current is monitored using a sense resistor. The sense

resistor has to be connected to the CS_CMP pin so that the STWBC-EP can detect the

current flowing into the inductor.

The DC/DC converter loop compares a reference target voltage applied on the

DCDC_DAC_REF pin with the feedback voltage connected to the CMP_OUT_V pin. The

CMP_OUT_V signal is a partition of the DC/DC output voltage.

The DCDC_DAC_REF reference voltage is variable in order to adjust the DC/DC output

voltage depending on wireless power solution requirements. The DCDC_DAC_REF is

generated by filtering the PWM signal present on the DCDC_DAC pin. A second order

passive filter is required.

The DC/DC output voltage is monitored by the STWBC-EP using the VTARGET pin. The

VTARGET should be generated as a partition of the DCDC output voltage.

In order to enhance the efficiency at the medium and low load, the DC/DC converter can

operate in the quasi-resonant mode. To do so, the STWBC-EP monitors the

demagnetization of the inductor using the DEMAGNET pin.