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high. However, the BPE must not be disabled when it is active (in critical supply levels 0 through 3). The BPE can be

disabled safely at any time that it is inactive. The input to the BPE controller is selected using the BPE_SRC_SEL bit.

By default, the input to the BPE controller is the measurement ADC PVDD channel. If the selected measurement ADC

channel is not already active, enabling the BPE will automatically enables it. The sample rate and filter settings for the

measurement ADC determine the speed at which the BPE updates.

SPEAKER PLAYBACK DATA PATH

BPE

CONTROLLER

LIMITER

GAIN

REDUCTION

PVDD SUPPLY

VBAT SUPPLY

MEAS

ADC

BPE_SRC_SEL

Figure 27. BPE Block Diagram

BPE State Controller and Level Thresholds

There are a total of four BPE critical supply levels, each with individually programmable thresholds. The thresholds for

each level are configured with the BPE_L0_VTHRESH to BPE_L3_VTHRESH bit fields respectively. The BPE state

controller monitors the measurement ADC channel results and automatically makes state changes.

Table 9. Brownout-Prevention Engine Levels

THRESHOLD NAME

CONDITION

BPE Inactive

VSUPPLY > Critical Supply Level 3

Critical Supply Level 3

Critical Supply 3 ≥ VSUPPLY > Critical Supply Level 2 + Hysteresis

Critical Supply Level 2

Critical Supply Level 2 ≥ VSUPPLY > Critical Supply Level 1 + Hysteresis

Critical Supply Level 1

Critical Supply Level 1 ≥ VSUPPLY > Critical Supply Level 0 + Hysteresis

Critical Supply Level 0

VSUPPLY ≤ Critical Supply Level 0

The brownout engine supports hysteresis on the levels. This behaves as follows:

● When in level N, transition to level N + 1 when VSUPPLY stays above (level N threshold) + (hysteresis)

● When in level N, transition to level N - 1 when VSUPPLY falls below level N threshold

The amount of hysteresis is defined by the BPE_VTHRESH_HYST register. The hysteresis is only applied to the

thresholds when supply voltage is increasing. The amount of hysteresis can be defined as larger than the distance

between two levels.

Thresholds must be configured so that the level N threshold is greater than the sum of the level N - 1 threshold and the

hysteresis. For example, if the level 2 threshold is set to 3.15V and hysteresis is set to 25mV, then the level 3 threshold

must be set to 3.1875V or higher.

The current level that the BPE is in can be read-back using the BPE_STATE register. The BPE_LOWEST register

contains the lowest BPE level that the controller has visited since the last time the BPE_LOWEST register was read.

MAX98396

20V Digital Input Class-DG Amplifier with I/V

Sense and Brownout Prevention

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