PCM5252 datasheet(39/119 Pages) TI1

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OUTLP

OUTRN

OUTLN

OUTRP

Left Differential Output

Right Differential Output

RC LPF

Optional RC Low-Pass Filter

470W

4.3nF

P Output

470W

N Output

PCM5252

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SLASE63 – NOVEMBER 2014

9.7 DAC and Differential Analog Outputs

9.7.1 Analog Outputs

The PCM5252 devices include a two-channel DAC, with differential outputs. Each pin has a full-scale output

voltage is 2.1Vrms with ground center output. This equates to a 4.2Vrms differential output. A dc-coupled load is

supported in addition to an ac-coupled load, if the load resistance conforms to the specification. The PCM5252

DAC outputs on the OUTLP, OUTLN, OUTRP, and OUTRN terminals have market-leading low out-of-band

noise, which offer up to 20dB lower out-of-band noise compared with existing DAC technology.

Many applications require an external low-pass RC filter (470

Ω + 1.2nF) to provide sufficient out-of-band noise

rejection. This RC filter provides the added advantage of improved protection against ESD damage.

The PCM5252 can also support single ended outputs, using OUTLP and OUTRP respectively. A single 470

and 2.2nF capacitor can be used on each pin in single ended mode.

The choice between VREF and VCOM modes affects the maximum output level. This is explained in Voltage

Reference and Output Levels.

Figure 61. Optional Low Pass Filters

9.7.2 Choosing Between VREF and VCOM Modes

VREF mode is the default configuration. This mode allows full 2.1Vrms signal output. As shown in Recommended

Operating Conditions, the minimum AVDD to avoid clipping is 3.2V.

VCOM mode allows setting a custom common-mode voltage when required by the application. This somewhat

limits the output signal swing before clipping.

9.7.2.1 Voltage Reference and Output Levels

The PCM5252 has an internal, fixed band-gap reference voltage, with default operation in VREF mode. No

external decoupling capacitor is required for this mode.

The PCM5252 can be operated with a common-mode voltage output (VCOM mode) at the VCOM pin by setting

Page 1, Register 1, D(0) to 1. In this mode, an external decoupling capacitor is required.

When using this DAC in VREF mode, the output-signal voltage is independent of the power-supply voltage: The

D/A conversion gain in VREF mode yields a 2.1Vrms output voltage with a digital full-scale input. However, in

VREF mode, an output waveform may clip due to the limitations that may be present in the analog power supply

voltage. On the other hand, the full-scale output voltage in VCOM mode is proportional to the analog power

supply AVDD. Example, (2.1 × AVDD / 3.3) Vrms.

9.7.2.2 Mode Switching Sequence, From VREF Mode to VCOM Mode

Following register setting sequence is recommended for changing VREF mode to VCOM mode.

1. Page 0 / Register 2

RQST = 1: Standby mode

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