NPM1100-CAAA-R datasheet(29/58 Pages) NORDIC

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Core components

When VINT is above VSYSBUCKMIN, the buck regulator is enabled and its output voltage is available at

VOUTB.

BUCK features two modes of operation: hysteretic and PWM. Hysteretic mode offers efficiency for the

full range of supported load currents. PWM mode provides a clean supply operation due to a constant

switching frequency, FBUCK. This provides optimal coexistence with RF circuits. BUCK can automatically

change between Hysteretic and PWM modes. Modes are controlled by the

MODE pin. The state of the

MODE pin can be changed at any time.

6.3.1 Output voltage selection (VOUTBSET0, VOUTBSET1)

BUCK output voltage selection pins

VOUTBSET0 and VOUTBSET1 should be hardwired to DEC, VSYS, or

AVSS. Do not toggle these pins during operation.

VOUTBSET1

VOUTBSET0

VOUTB voltage

LOW

1.8 V

LOW

HIGH

2.1 V

HIGH

LOW

2.7 V

HIGH

3.0 V

Table 16: Output voltage selection

For BUCK to supply the desired output voltage, VINT must be VDROPOUT_BUCK greater than the voltage on

VOUTB.

When supplied from battery, the following equation gives the VINT:

VINT = VBAT – IBAT x RONCHARGER

Here, IBAT is the current being drawn from the battery.

6.3.2 BUCK mode selection (MODE)

In Automatic mode, BUCK selects Hysteretic mode for low load currents, and PWM mode for high load

currents.

This maximizes efficiency over the full range of supported load currents. In PWM mode, BUCK provides

a clean supply operation due to constant switching frequency and lower voltage ripple. This allows for

optimal coexistence with RF circuits. The

MODE pin can be changed at any time.

MODE

BUCK operation mode

LOW

Automatic selection between Hysteretic and PWM

modes

HIGH

PWM mode

Table 17: BUCK mode selection

6.3.3 Component selection

Recommended values for the inductor are shown in the following table.

4445_367 v1.0

NPM1100-CAAA-R Datasheet(PDF) 29 Page - Nordic Semiconductor

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