WM8944BECSSLASHR datasheet(97/165 Pages) CIRRUS

97 / 165 page

WM8944B

Rev 4.3

THERMAL SHUTDOWN

The WM8944B incorporates a temperature sensor which detects when the device temperature is

within normal limits. The temperature status can be read at any time from the TEMP_STS bit, as

described in Table 68. This bit can be polled at any time, or may output directly on a GPIO pin, or may

be used to generate Interrupt events.

The temperature sensor can be configured to shut down the speaker outputs in the event of an

overtemperature condition. This is configured using the THERR_ACT register field.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R17 (11h)

Status Flags

TEMP_STS

Thermal Sensor status (Read only)

0 = Normal

1 = Overtemperature

R42 (2Ah)

Output ctrl

THERR_ACT

Thermal Shutdown enable

0 = Disabled

1 = Enabled

When THERR_ACT = 1, then an

over temperature condition will

cause the speaker outputs to be

disabled.

Table 68 Thermal Shutdown Control

Note: For minimum power down current the thermal shutdown should be disabled by setting the

THERR_ACT bit in register R42 (2Ah) bit 15 low.

POWER ON RESET

The WM8944B includes a Power-On Reset (POR) circuit, which is used to reset the digital logic into a

default state after power up. The POR circuit derives its output from LDOVDD and DCVDD. The

internal POR

¯¯¯ signal is asserted low when either LDOVDD or DCVDD are below minimum thresholds.

The specific behaviour of the circuit will vary, depending on relative timing of the supply voltages.

Typical scenarios are illustrated in Figure 42 and Figure 43.

DCVDD

Vpord_on

POR

Undefined

Internal POR

Internal POR active

Device Ready

LDOVDD

Vpora

Vpora_off

Figure 42 Power On Reset Timing

– LDOVDD Enabled First

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