CS4525 datasheet(46/98 Pages) CIRRUS

46 / 98 page

DS726PP1

CS4525

gradual voltage ramp minimizes output transients while the DC blocking capacitor is charged and dis-

charged. The Popguard has no effect on the PWM_SIG outputs nor the auxiliary serial output.

PWM Popguard is disabled by default; to enable it, the RmpSpd[1:0] register must be set to any value

other than 11. PWM Popguard should only be used for has when the power outputs are configured for

stereo half-bridge with full-bridge sub per Section 6.1.7.1. The RAMP_CAP pin must be connected to the

VP supply through a 0.033 µF capacitor whenever PWM Popguard is enabled, as shown in Figure 19.

Table 9. Typical Ramp Times for Various VP Voltages

PWM Popguard’s output ramp time will vary depending on the voltage applied to VP and the value of the

RmpSpd[1:0] bits; typical ramp times are listed in Table 9. All output channels are affected by the Rm-

pSpeed[1:0] bits, and PWM Popguard is disabled by default.

6.1.8

Logic-Level PWM Outputs

The CS4525 has two configurable logic-level PWM outputs, PWM_SIG1 and PWM_SIG2. These outputs

can be used as either digital input to an external PWM amplifier such as the CS4412, or as an analog

input to a headphone amplifier or a line-out amplifier.

To eliminate power-up pops when used to supply an external PWM amplifier, the CS4525 implements the

same click-free start-up function on the PWM_SIG outputs as it does for its own powered PWM outputs.

This function can only be utilized if the PWM amplifier has an initial transition delay feature, such as the

CS4412A. To eliminate power-up and power-down pops when used to supply an analog output circuit,

the PWM_SIG outputs support a high-impedance state that is controlled by the HiZPSig bit in the

VP Voltage

Typical Ramp Up Times

RmpSpd[1:0] = 00

RmpSpd[1:0] = 01

RmpSpd[1:0] = 10

RmpSpd[1:0] = 11

12 V

2.16 seconds

2.20 seconds

Instant (No Ramp)

15 V

1.74 seconds

1.76 seconds

1.78 seconds

Instant (No Ramp)

18 V

1.40 seconds

1.42 seconds

1.44 seconds

Instant (No Ramp)

Referenced Control

RmpSpeed[1:0] ................... “Ramp Speed (RmpSpd[1:0])” on page 75

PDnAll ................................. “Power Down (PDnAll)” on page 89

PDnOutX ............................. “Power Down PWM Power Output X (PDnOutX)” on page 88

Left

Speaker

Right

Speaker

Subwoofer

0.033 uF

+8V to +18V

Full-

bridge

Filter

CS4525

OUT1

OUT2

OUT3

OUT4

Half-

bridge

Filter

Half-

bridge

Filter

Figure 19. Popguard Connection Diagram

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