VDCDC_IN
** VDD_1P8
To power
other circuits
VDD_0
VDD_1
VDDA
** VDD_1P5
VDD_RF1
VDD_RF2
VDD_RF3
** VREFH
DCDC_CFG
DCDC_LP
* Need 1.1 V min to start,
the supply can drop to 0.9 V
after DC-DC converter settles
** Both pins are outputs
of the DCDC converter
in Buck mode
*** Some packages have the
option to connect it to VDDA
internally
DCDC_LN
DCDC_GND
10 µH
10 µF
PSWITCH
0.1 µF
100 nH
0.1 µF
0.1 µF
10 µF
12 pF
1 µF
100 nH
12 pF
10 µF
*0.9 - 1.795 V
*
Figure 4. MKW DC-DC in Boost mode
3.4 Buck-Boost mode
The MKW DC-DC converter does not support Buck-Boost switching. Based on the battery voltage range for the system, the
application should be designed for either Buck or Boost configuration. It is not possible to switch modes on the fly. For example,
a hypothetical configuration circuit switching from buck to boost mode is not allowed. The DC-DC mode must change after the
power is turned off and the pin configuration correctly set.
4 DC-DC converter software setup
The DC-DC operates in two different modes; Continuous Mode and Pulsed Mode. In Continuous Mode, the control loop keeps
the PWM ON, constantly adjusting the pulse width to maintain the two output voltages.
The Pulsed Mode option periodically generates a PWM burst, recharging the bulk capacitors. When the voltage falls below the
configured threshold, the DC-DC module starts the PWM, and after voltage reaches the maximum threshold value, it turns off,
starting a new cycle. Pulsed mode is automatically entered whenever the MCU enters VLPR, VLPW, VLPS, LLS, or VLLSx modes.
Note that it is possible to, by software, select either Continuous or Pulsed Mode when entering VLPR, VLPW, or VLPS modes.
Below oscilloscope plots show the difference between Continuous and Pulsed modes.
NXP Semiconductors
DC-DC converter software setup
MKW4xZ/3xZ/3xA/2xZ DC-DC Power Management, Rev. 3, 04 June 2021
Application Note
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