PCM3070 datasheet(39/50 Pages) TI2

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PCM3070

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SLAS724A – SEPTEMBER 2008 – REVISED NOVEMBER 2014

12 Power Supply Recommendations

To power up the device, a 3.3V system rail (1.9V to 3.6V) can be used. The IOVDD voltage can be in the range

of 1.1V – 3.6V. Internal LDOs can generate the appropriate digital and analog core voltages when configured to

do so. For maximum flexibility, the respective voltages can also be supplied externally, bypassing the built-in

LDOs. To support high-output drive capabilities, the output stages of the output amplifiers can be driven from the

analog core voltage or the 1.9…3.6V rail used for the LDO inputs (LDO_in).

The AVDD and LDOIN power inputs are used to power the analog circuits including analog to digital converters,

digital to analog converters, programmable gain amplifiers, headphone amplifiers, etc. The analog blocks in

PCM3070 have high power supply rejection ratio, however it is recommended that these supplies be powered by

well regulated power supplies like low dropout regulators (LDO) for optimal performance. When these power

terminals are driven from a common power source, the current drawn from the source will depend upon blocks

enabled inside the device. However as an example when all the internal blocks powered are enabled the source

should be able to deliver 150mA of current.

The DVDD powers the digital core of PCM3070, including the miniDSP, the audio serial interface, control

interfaces (SPI or I2C), clock generation and PLL. The DVDD power can be driven by high efficiency switching

regulators or low drop out regulators. When the miniDSP_A and miniDSP_D are enabled in programmable mode

and operated at peak frequencies, the supply source should be able to able to deliver approx 100mA of current.

When the PRB modes are used instead of programmable miniDSP mode, then the peak current load on DVDD

supply source could be approximately 20 mA.

The IOVDD powers the digital input and digital output buffers of PCM3070. The current consumption of this

power depends on configuration of digital terminals as inputs or outputs. When the digital terminals are

configured as outputs, the current consumption would depend on switching frequency of the signal and the load

on the output terminal, which depends on board design and input capacitance of other devices connected to the

signal.

Refer to Figure 19 for recommendations on decoupling capacitors.

For more detailed information see the PCM3070 Application Reference Guide, SLAU332.

13 Layout

13.1 Layout Guidelines

Each system design and PCB layout is unique. The layout should be carefully reviewed in the context of a

specific PCB design. However, the following guidelines can optimize PCM3070 performance:

•

Connect the thermal pad to ground.

•

The decoupling capacitors for the power supplies should be placed close to the device terminals. Figure 19

shows the recommended decoupling capacitors for the PCM3070.

•

The PCM3070 internal voltage references must be filtered using external capacitors. Place the filter

capacitors on REF near the device terminals for optimal performance.

•

For analog differential audio signals, the signals should be routed differentially on the PCB for better noise

immunity. Avoid crossing of digital and analog signals to avoid undesirable crosstalk.

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