In Pulsed mode, the DC-DC PWM is turned on until the output capacitor is charged to the configured high trigger limit. Then the
DC-DC PWM is temporarily turned off until the output voltage drops to the lower trigger limit, whereby a PWM burst then charges
the output capacitor again. In general, pulsed mode is entered when the SoC enters a low-power mode, and is in continuous mode
when the SoC is in a RUN mode. Software can configure which DC-DC mode (Continuous or Pulsed) is selected when entering
some low-power modes. Pulsed mode improves energy efficiency in low-power modes where the current does not exceed 0.5 mA.
VDD_1P8 should supply VDD1, VDD2, and VDDA through external PCB traces and, within the current capability, may also power
other circuits of the system. The VDD_1P5 is designed to supply just the Radio Frequency circuit. This power supply should be
externally connected to only the VDD_RF pins.
The DC-DC SMPS uses the voltage VDD_0/1 as feedback for the loop control of the VDD_1P8 output, so application hardware
designer must ensure the correct return signal without series resistance from VDD_1P8 to VDD_0/1.
It is not possible to configure the DC-DC for buck or boost modes while sourcing VDD_0/1 from an external source.
3 DC-DC Power modes
3.1 Bypass mode
In Bypass mode, the DC-DC converter is disabled. Both the VDD_1P8 and VDD_1P5 are inputs. MKW devices require individual
DC supply for the VDDx, VDDA, VDD_1P8, VDD_1P5, and VDD_RFx domains to be functional.
Below is the minimum recommended circuit configurations for DC-DC converter in Bypass mode.
VDCDC_IN
VDD_1P8
VDD_0
VDD_1
VDDA
VDD_1P5
VDD_RF1
VDD_RF2
VDD_RF3
* VREFH
DCDC_CFG
DCDC_LP
* Some packages have the
option to connect it to VDDA
internally
DCDC_LN
DCDC_GND
10 µF
PSWITCH
10
9
11
12
13
8
0.1 µF
1.71 - 3.6 V
1.45 - 3.6 V
1.71 - 3.6 V
0.1 µF
12 pF
0.1 µF
0.1 µF
0.1 µF
12 pF
10 µF
10 µF
Figure 1. MKW DC-DC in Bypass Mode
3.2 Buck mode
In Buck mode, the input voltage VDCDC_IN is converted to a lower voltage which is output to the VDD_1P8 and VDD_1P5 pins.
These pins are initialized to the below default startup values (after POR resets only), and then by software, those values may
be changed:
VDD_1P8 = 1.8 V and VDD_1P5 = 1.5 V
NXP Semiconductors
DC-DC Power modes
MKW4xZ/3xZ/3xA/2xZ DC-DC Power Management, Rev. 3, 04 June 2021
Application Note
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