9 Power Supply Recommendations

The TUSS4440 device is designed to operate from two independent supplies, a driver supply and a regulated supply.

The driver input voltage supply (VPWR) range can operate from 5 V to 24 V (when VDRV is disabled) or to 36 V (when VDRV is enabled). In applications where the TUSS4440 device may be exposed to battery transients and reverse battery currents, use external component-safeguards, such as component D1 or parallel TVS diodes, to help protect the device. If the input supply is placed more than a few inches from the TUSS4440 device, additional bulk capacitance may be required in addition to the ceramic bypass capacitors near the VPWR pin. In the event VDRV is disabled, the electrolytic capacitor at the VDRV pin is intended to act as a fast discharge capacitor during the bursting stage of the TUSS4440 device. The center-tap transformer can be supplied with an independent center-tap voltage that is isolated from the VPWR and VDRV pins, but must remain within half the specified maximum voltage rating of the OUTA and OUTB outputs. If the center-tap voltage is to be supplied by an independent source, the VDRV pin can remain floating, and VDRV should be disabled.

The regulated supply (VDD) is used as the supply reference for the analog front end, filtering, and analog output blocks, so this supply should be stable for maximum performance. TI recommends using an LDO or other regulated external power source with bypass capacitor placed closely to the VDD pin. As VDD becomes less stable, the noise floor of the VOUT signal will increase, and result in a loss of long range object detection as a consequence.

To prevent damage to the device, always avoid hot-plugging or providing instantaneous power at the VPWR and VDRV pins at start-up, unless these pins are properly protected with an RC filter or TVS diode to minimize transient effects. VPWR must always be equal to or greater than the value present at VDRV.