WM8962B datasheet(160/295 Pages) WOLFSON

160 / 295 page

WM8962

160

Rev 4.3

INTERNAL OSCILLATOR CONTROL

The internal oscillator is enabled by OSC_ENA. The oscillator is suitable for operation at 24MHz,

using a suitable external crystal. The oscillator should be enabled when an external crystal is

connected to MCLK to provide clocking; it should be disabled when an external clock is connected to

MCLK.

The OSC_ENA register is controlled automatically under certain circumstances, as described below.

The associated control register, CLKREG_OVD, is defined in the “Automatic Clocking Configuration”

section, (see “Clocking and Sample Rates”).

When a logic 0 is applied on the GPIO5 pin, the OSC_ENA register is set 0. In this case, the

OSC_ENA register is locked to prevent accidental writes to this register. The OSC_ENA register can

be unlocked by setting the CLKREG_OVD bit.

When a logic 1 is applied on the GPIO5 pin, the OSC_ENA register defaults to 1. In this case, the

default (1) is selected on the rising edge of GPIO5; other settings can then be selected by writing to

the OSC_ENA register as normal.

Note that, if GPIO functionality is required on the GPIO5 pin, then the CLKREG_OVD bit must be set

to ‘1’ in order to select normal read/write control of the OSC_ENA register.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R129 (81h)

PLL 2

OSC_ENA

Internal Oscillator Enable

0 = Disabled

1 = Enabled

If CLKREG_OVD = 0, then OSC_ENA is

controlled by the GPIO5 pin.

If CLKREG_OVD = 0 and GPIO5 = 0,

then OSC_ENA = 0 and cannot be

changed by the Control Interface.

If CLKREG_OVD = 0 and GPIO5 = 1,

then OSC_ENA = 1 by default, but the

value can be changed via the Control

Interface.

If CLKREG_OVD = 1 then OSC_ENA =

1 by default, but the value can be

changed via the Control Interface.

Table 105 Internal Oscillator Enable

The crystal oscillator requires an external crystal on the XTI and XTO pins The WM8962 provides

internal loading capacitors for the crystal, removing the need for any external capacitors, as shown in

Figure 59.

Crystal Oscillator

XTI / MCLK

XTO

Figure 59 Crystal Oscillator

The internal loading capacitance

is detailed in the “Electrical Characteristics”. Selection of the correct

crystal component is important to ensure best accuracy and stability of the oscillator.

In cases where the internal loading capacitance differs from the required value (eg. due to

characteristics of the chosen crystal, or due to additional capacitive effects of PCB tracks), it is

possible to compensate for this within the WM8962, using the control registers described below.

WM8962B Datasheet(PDF) 160 Page - Wolfson Microelectronics plc

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