16

CS4361

Confidential Draft

2/12/08

4.6

Output Transient Control

The CS4361 uses Popguard technology to minimize the effects of output transients during power-up and

power-down. When implemented with external DC-blocking capacitors connected in series with the audio

outputs, this feature eliminates the audio transients commonly produced by single-ended, single-supply

converters. To make the best use of this feature, it is necessary to understand its operation.

4.6.1

Power-Up

When the device is initially powered up, the audio outputs, AOUT1-6, are clamped to VQ, which is initially

low. After RST is released and MCLK is applied, the outputs begin to ramp with VQ towards the nominal

quiescent voltage. This ramp takes approximately 200 ms to complete. The gradual voltage ramping al-

lows time for the external DC-blocking capacitors to charge to VQ, effectively blocking the quiescent DC

voltage. Audio output begins approximately 2000 sample periods after valid LRCK and SDIN are supplied

(and SCLK, if used).

4.6.2

Power-Down

To prevent audio transients at power-down, the DC-blocking capacitors must fully discharge before turn-

ing off the power. In order to do this, either stop MCLK or hold RST low for a period of about 250 ms before

removing power. During this time, voltage on VQ and the audio outputs discharge gradually to GND. If

power is removed before this 250 ms time period has passed, a transient will occur when the VA supply

drops below that of VQ. There is no minimum time for a power cycle; power may be reapplied at any time.

When changing clock ratio or sample rate, it is recommended that zero data (or near zero data) be present

on SDIN for at least 10 LRCK samples before the change is made. During the clocking change, the DAC

outputs will always be in a zero data state. If non-zero audio is present at the time of switching, a slight

click or pop may be heard as the DAC output automatically goes to its zero data state.

4.7

Grounding and Power Supply Decoupling

As with any high-resolution converter, the CS4361 requires careful attention to power supply and grounding

arrangements to optimize performance. Figure 6 shows the recommended power arrangement, with VA

connected to a clean +5 V supply. For best performance, decoupling and filter capacitors should be located

as close to the device package as possible, with the smallest capacitors placed closest.

4.8

Analog Output and Filtering

The analog filter present in the CS4361 is a switched-capacitor filter followed by a continuous-time, low-

pass filter. Its response, combined with that of the digital interpolator, is given in Figures 14 - 21. The rec-

ommended external analog circuitry is shown in the “Typical Connection Diagram” on page 11.

The analog outputs are named AOUT1-6. The SDIN1 feeds AOUT1 as the ‘Left’ marked data and AOUT2

as the ‘Right’ marked data. The SDIN2 feeds AOUT3 as the ‘Left’ marked data and AOUT4 as the ‘Right’

marked data. The SDIN3 feeds AOUT5 as the ‘Left’ marked data and AOUT6 as the ‘Right’ marked data.