CS4525 datasheet(46/98 Pages) CIRRUS

46 / 98 page

DS726PP3

CS4525

charged and discharged. The Popguard technology has no effect on the PWM_SIG outputs nor the aux-

iliary serial output.

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

any value other than 11. The PWM Popguard feature should only be used 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 the PWM Popguard technology is

enabled, as shown in Figure 19.

Table 9. Typical Ramp Times for Various VP Voltages

The 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 RmpSpeed[1:0] bits,

and PWM Popguard feature 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

EQ Config register. This bit is active-low and cleared by default. To use the PWM_SIG outputs, the HiZ-

PSig bit must be set to enable the PWM_SIG output drivers.

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 89

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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