The DAC_DVDD supply is required from the system to power several portions of the device. As shown in Figure 125, it provides power to the DVDD_REG pin and the CPVDD pin. Proper connection, routing, and decoupling techniques are highlighted in the EVM User's Guide (as well as the Application and Implementation section and the Layout Examples section) and must be followed as closely as possible for proper operation and performance. Deviation from the guidance offered in the TAS3251EVM User's Guide, which follows the same techniques as those shown in theApplication and Implementation section, can result in reduced performance, errant functionality, or even damage to the TAS3251 device.
Some portions of the device also require a separate power supply that is a lower voltage than the external DAC_DVDD supply. To simplify the power supply requirements for the system, the TAS3251 device includes an integrated low-dropout (LDO) linear regulator to create this supply. This linear regulator is internally connected to the DAC_DVDD supply and its output is presented on the DVDD_REG pin, providing a connection point for an external bypass capacitor. It is important to note that the linear regulator integrated in the device has only been designed to support the current requirements of the internal circuitry, and should not be used to power any additional external circuitry. Additional loading on this pin could cause the voltage to sag, negatively affecting the performance and operation of the device.
The outputs of the high-performance DACs used in the TAS3251 device are ground centered, requiring both a positive low-voltage supply and a negative low-voltage supply. The positive power supply for the DAC output stage is taken from the DAC_AVDD pin, which can be connected to the DAC_DVDD supply provided by the system. A charge pump is integrated in the TAS3251 device to generate the negative low-voltage supply. The power supply input for the charge pump is the CPVDD pin. The CPVSS pin is provided to allow the connection of a filter capacitor on the negative low-voltage supply. As is the case with the other supplies, the component selection, placement, and routing of the external components for these low voltage supplies are shown in the TAS3251 EVM User's Guide and should be followed as closely as possible to ensure proper operation of the device.