Design information

AN2612

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3.4

Design information for power management

3.4.1

Recommendations for the codec layout

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Use an electrolytic capacitor at each branch of the Vcc power track.

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Place decoupling capacitors as close as possible to the Vcc and ground pins.

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Dissipate the heat with a large ground plane.

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Place the PLL filter components as close as possible to pin FILT.

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For differential applications create symmetrical paths for the output stage.

Please refer to the STA529 datasheet/applications note for details of the above points.

3.4.2

Power supply considerations

there is a risk that the switching noise will appear on the power supply lines. Furthermore

this switching frequency is in the audio band. So, if the supply is shared with the audio stage

and insufficient decoupling is employed, it could lead to a noisy audio line output when used

in single-ended mode, as shown in Figure 13, upper photo. In order to minimize this

possibility it was decided to employ separate regulators on the BT_HTS_RX_R2 board for

the RF part and for the analog audio part. The lower photo of Figure 13 shows the resulting

line output for single-ended mode.

Figure 12 shows how the power management is implemented on the board. IC5, IC6 are

two 3.3 V low dropout (LDO) regulators (ST reference LD2985AM33). 3V3_BT is the supply

brands of LDO are also usable, but they should have a high PSRR and a good regulation

supply.

Figure 12.

Power management