STPM098C datasheet(90/110 Pages) STMICROELECTRONICS

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Figure 75. DPM configuration efficiency-load current - Example 2

Load Current L2

Efficiency L2

N=1

N=2

Iload5

3.14.7.2

Active diode emulation (ADE)

When operating in a single phase configuration under very light load condition, STPM098C allows a further

efficiency boosting by forcing the controller to work in DCM (discontinuous current mode) and consequently

reducing DrMOS conduction losses.

The n-th loop ADE activation can be disabled separately by means of a dedicated PMBus™ command as follows:

Table 70. ADE disable bit

CTRL_PFM_DIS

Description

ADE enabled (default)

ADE disabled

If ADE is disabled, when DPS reduces the number of active phases to 1, the controller will still works in CCM.

CCM/DCM boundary condition is sensed by a dedicated zero-current comparator on ISENn which constantly

monitors the current level.

If ISENn – CFILT/VREF1 ≤ ZC_OFFSET occurs for an interval longer than ZC_MASK_DELAY, the related PWM

output is overridden to HIZ. PWM masking is removed at the next switching cycle.

Zero current detection threshold ZC_OFFSET can be offset with respect to zero level by means of two dedicated

PMBus™ commands OFSZC<1:0> and GAINZC<3:0> as follows:

ZC_OFFSET = ZC_OFFSET (OFSZC) + ZC_OFFSET (GAINZC)

Table 71. ZC offset1 configuration bit

OFSZC1

OFSZC 0

Description

ZC_OFFSET = 0 mV (default)

ZC_OFFSET = 8 mV

ZC_OFFSET = 16 mV

ZC_OFFSET = 24 mV

STPM098C

Functional description

DS14440 - Rev 1

page 90/110

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