WM8321 datasheet(68/253 Pages) WOLFSON

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WM8321

Production Data

PD, February 2012, Rev 4.0

15.9 FAULT PROTECTION

Each of the DC-DC Buck Converters (1 to 4) is monitored for voltage accuracy and fault conditions.

An undervoltage condition is set if the output voltage falls below the required level by more than the

applicable undervoltage margin, as specified in Section 7.1.

Each LDO Regulator (1 to 10) is monitored for voltage accuracy and fault conditions. An undervoltage

condition is set if the output voltage falls below the required level by more than the undervoltage

margin, as specified in Section 7.2.

The DCm_ERR_ACT and LDOn_ERR_ACT fields configure the fault response to an Undervoltage

condition. An Interrupt is always triggered under this condition (see Section 15.12); additional action

can also be selected independently for each converter / regulator. The options are to ignore the fault,

shut down the converter, or to shut down the system. To prevent false alarms during short current

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

If a fault condition is detected, and the selected response is to shut down the converter or regulator,

then the associated _ENA and _STS fields are reset to 0, as described in Section 15.2.

If a fault condition is detected, and the selected response is to shut down the system, then a Device

Reset is triggered, as described in Section 24.1, forcing a transition to the OFF state. The WM8321

will automatically return to the ON state after performing the Device Reset.

Note that, if the fault condition persists, then a maximum of 6 Device Resets will be attempted to

initiate the start-up sequence. If the sequence fails more than 6 times, the WM8321 will remain in the

OFF state until the next valid ON state transition event occurs.

Note that DC-DC1 and DC-DC2 overvoltage and high current conditions can be detected and

reported as described in Section 15.10. The DCm_ERR_ACT fields have no relation to these

conditions.

The DC-DC3 and DC-DC4 Converters have a selectable overvoltage protection feature, controlled by

DC3_OVP or DC4_OVP. This affects the converter response when the applicable converter is

enabled or when its output voltage is increased. When the overvoltage protection is enabled, there is

less overshoot in the output voltage, but some oscillation may occur as the voltage settles. This

function should only be enabled if steep load transients are present on the output of the DC-DC

Converter and if voltage overshoot is critical.

15.10 MONITORING AND FAULT REPORTING

Each of the DC-DC Converters (1 to 4) and LDOs (1 to 10) is monitored for voltage accuracy and fault

conditions. An undervoltage condition is detected if the voltage falls below the required level by more

than a pre-determined tolerance. If an undervoltage condition occurs, then this is indicated using the

corresponding status bit(s) defined in Section 15.11.5. An undervoltage condition also triggers an

Undervoltage Interrupt (see Section 15.12). Additional actions to shut down the converter or perform

a Device Reset may also be selected.

The Internal LDO (LDO13) is also monitored for voltage accuracy and fault conditions. An

undervoltage condition in LDO13 is indicated using the INTLDO_UV_STS bit. This undervoltage

condition also causes an OFF transition to be scheduled, as described in Section 11.3.

DC-DC Converters 1 and 2 are monitored for overvoltage conditions. An overvoltage condition is set if

the voltage is more than 100mV above the required level. If an overvoltage condition occurs, then this

is indicated using the corresponding status bit(s). Note that there is no Interrupt or other selectable

response to an overvoltage condition.

The current draw on DC-DC Converters 1 and 2 can be monitored against user-programmable

thresholds in order to detect a high current condition. This feature is enabled using

DCm_HC_IND_ENA and the current threshold is set using DCm_HC_THR. Note that the high current

threshold is not the same as the maximum current capability of the DC-DC Converters, but is set

according to the application requirements. If a high current condition occurs, then this is indicated

using the corresponding status bit(s). A high current condition also triggers a High Current Interrupt

(see Section 15.12).

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