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 2.1 V min to start,
the supply can drop to 1.8 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
100 kΩ
SW1
*1.8 - 4.2 V
PSWITCH
0.1 µF
100 nH
0.1 µF
0.1 µF
10 µF
12 pF
1 µF
100 nH
12 pF
10 µF
*
Figure 2. MKW DC-DC in Buck mode (manual start)
3.2.2 Buck Mode – Auto start
This mode allows the DC-DC to automatically turn on immediately after power is applied to the device. Typical startup time is 2.3
ms and varies with the loading of the converter.
As the PSWITCH is always tied to VDCDC_IN, there is no possibility to turn off the DC-DC SMPS after it starts. If software attempts
to shut down the module, the device enters in an abnormal state, requiring a power cycle to recover the unit.
Below is the recommended circuit for DC-DC converter in Buck Auto Start mode:
NXP Semiconductors
DC-DC Power modes
MKW4xZ/3xZ/3xA/2xZ DC-DC Power Management, Rev. 3, 04 June 2021
Application Note
4 / 28
