WM8352 datasheet(145/336 Pages) WOLFSON

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Production Data

WM8352

PD, February 2011, Rev 4.4

145

15.2.2

CURRENT LIMIT SWITCH BULK DETECTION CONTROL

The Current Limit Switch can be connected to voltages which may be higher than the device LINE

voltage. To support this capability, the switch is powered from the highest available voltage; this

requires a bulk detection circuit in order to select the highest available voltage. The bulk detection

circuit is always enabled whenever the Current Limit Switch is enabled.

It is possible to control whether the bulk detection circuit is enabled or not when the Current Limit

Switch is disabled. This is controlled in Active mode by the LS_PROT bit, and in Hibernate mode by

the LS_HIB_PROT bit.

Disabling the Bulk Detection circuit will reduce power consumption. It is important to note, however,

that the Bulk Detection circuit should always be enabled if voltages greater than LINE could be

present on IP or OP. This applies regardless of whether the Current Switch is open or closed.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R199 (C7h)

Limit switch

control

LS_HIB_PRO

Controls the bulk detection circuit when

Limit Switch is disabled in Hibernate

mode.

0 = bulk detection disabled

1 = bulk detection enabled

LS_PROT

Controls the bulk detection circuit when

Limit Switch is disabled in Active mode.

0 = bulk detection disabled

1 = bulk detection enabled

Table 92 Current Limit Switch Bulk Detection Control

15.2.3

INTERRUPTS AND FAULT PROTECTION

The response to an over-current condition is selectable. To prevent false alarms during short current

surges, faults are only signalled if the fault condition persists.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R199 (C7h)

Limit switch

control

15:14

LS_ERRACT

[1:0]

Current limit detection behaviour

00 = ignore

01 = disable switch

10 = shut down system

11 = shut down system

Table 93 Fault Response for the Current Limit Switch

The limit switch has its own first-level interrupt, OC_INT (see Section 24). This contains a single

second-level interrupt, OC_LS_EINT, indicating an over-current condition. OC_LS_EINT can be

masked by setting the IM_OC_LS_EINT bit.

ADDRESS

BIT

LABEL

DESCRIPTION

R29 (1Dh)

Over Current

Interrupt Status

OC_LS_EINT

Limit Switch Over-current interrupt.

(Rising Edge triggered)

Note: This bit is cleared once read.

R37 (25h)

Over Current

Interrupt Mask

IM_OC_LS_EINT

Mask bit for Limit switch over-current

interrupt

When set to 1, IM_OC_LS_EINT masks

OC_LS_EINT in R29 and does not trigger

an OC_INT interrupt when OC_LS_EINT is

set).

Table 94 Current Limit Switch Interrupts

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