WM8993 datasheet(86/229 Pages) WOLFSON

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WM8993

Production Data

PD, November 2010, Rev 4.0

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R76 (4Ch)

Charge Pump

CP_ENA

Enable charge-pump digits

0 = disable

1 = enable

Note: Default value of R76[14:0]

(0x1F25h) must not be changed

when enabling/disabling the Charge

Pump

R81 (51h)

Class W 0

CP_DYN_PWR

Enable dynamic charge pump

power control

0 = charge pump controlled by

volume register settings (Class G)

1 = charge pump controlled by real-

time audio level (Class W)

Table 55 Charge Pump Control

If the headphone output drivers (HPOUT1L and HPOUT1R) are not used, then the Charge Pump and

the associated external components are not required. The Charge Pump and Headphone drivers

should not be enabled in this case (CP_ENA=0, HPOUT1L_ENA=0, HPOUT1R_ENA=0).

If the Charge Pump is not used, and the associated external components are omitted, then the

CPCA and CPCB pins can be left floating; the CPVOUTP and CPVOUTN pins should be grounded

as illustrated in Figure 24.

Note that, when the Charge Pump is disabled, it is still recommended that the CPVDD pin is kept

within its recommended operating conditions (1.71V to 2.0V).

CPVDD

WM8993

Charge Pump

CPVOUTP

CPVOUTN

CPFB1

CPFB2

CPGND

Figure 24 External Configuration when Charge Pump not used

DC SERVO

The WM8993 provides a DC servo circuit on the headphone outputs HPOUT1L and HPOUT1R in

order to remove DC offset from these ground-referenced outputs. When enabled, the DC servo

ensures that the DC level of these outputs remains within 1mV of ground. Removal of the DC offset

is important because any deviation from GND at the output pin will cause current to flow through the

load under quiescent conditions, resulting in increased power consumption. Additionally, the

presence of DC offsets can result in audible pops and clicks at power up and power down.

The recommended usage of the DC Servo is initialised by running the default Start-Up sequence as

described in the “Control Write Sequencer” section. The default Start-Up sequence executes a series

of DC offset corrections, after which the measured offset correction is maintained on the headphone

output channels. If a different usage is required, eg. if a periodic DC offset correction is required,

then the default Start-Up sequence may be modified according to specific requirements. The relevant

control fields are described in the following paragraphs and are defined in Table 56.

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