EFP01 datasheet(12/158 Pages) SILABS

12 / 158 page

3.2.1.4 Current Limiting

When powering EFP01 from weak power sources or sources with a high internal impedance, peak load currents at the converter output

can cause a large supply voltage droop at the input, increasing the risk of an unintended power-on reset. To alleviate these issues, it

may be necessary to limit the input current.

Note: EFP0111 is the only OPN that has its current limit enabled by default (on DCDC A).

Note: Because enabling the current limit will essentially current-starve the output, the system designer should validate the application

under the worst-case output load current.

On EFP01, the current limit is controlled by forcing a minimum time between the start of pulse events (TSW_MIN) and is configured by

BB_IRI_CON in the BB_CTRL6 register. BB_IRI_CON can be calculated based on the mode, the input voltage (VDDB), output voltage

(VOA), DCDC A inductor value (LA), peak current (IPK, set by BB_IPK), and the desired limited battery current (IBATT_LIMIT) as follows:

In buck mode: IBATT_LIMIT =

L × IPK 2

2 × TSW_MIN

(VDDB - VOA)

In boost mode: IBATT_LIMIT =

L × IPK 2

2 × TSW_MIN

(

VOA - VBOOST

VBOOST )

where TSW_MIN is programmed by BB_IRI_CON as follows:

TSW_MIN = 300ns × (2 × BB_IRI_CON + 1)

Note that the required BB_IRI_CON setting for a given current limit varies with the VDDB or VBOOST voltages and the peak current,

both variables that can change over battery voltage. An application requiring a fixed current limit over the entire range of the battery

may need to occasionally measure the VDDB voltage and recalculate / reprogram the BB_IRI_CON setting.

Note also that in configurations where the VOC LDO is used in parallel with the VOA output (e.g., Buck with LDO configuration), the

BB_IRI_CON bitfield in the BB_CTRL6 register will control the current limit when the converter is in DCDC mode and the

VOC_IRI_CON bitfield in the LDOC_BB_CTRL register will control the current limit when the converter is in LDO mode.

EFP01 Energy Friendly PMIC Family Data Sheet

System Overview

silabs.com | Building a more connected world.

Rev. 1.3 | 12

EFP01 数据表(PDF) 12 Page - Silicon Laboratories