User's Manual

24
5 Power Control
5.1 Power Supply Configuration
WT32 contains an internal battery charger and a switch mode regulator that is mainly used for internal
blocks of the module. The module can be powered from a single 3.3 V supply provided that VDD_CHG
is floating. Alternatively the module can be powered from a battery connected to VDD_BAT and using
an external regulator for VDD_IO. 1.8 V to 3.3 V supply voltage for VDD_IO can be used to give desired
signal levels for the digital interfaces of the module. USB, however, requires 3.3 V for proper operation
and thus, when USB is in use, 3.3 V for VDD_IO is mandatory.
AIO pins of the module use 1.8 V from the internal regulator and thus voltage level with these pins is
within 0 V and 1.8 V.
VDD_BAT
Switch mode 1,8 V
regulator
VDD_IO
Battery Charger
In
Out
VDD_CHG
AIO
Audio
RF
Flash
PIO
USB
UART
PCM
VREG_ENA
Figure 4: Power supply configuration of WT32
5.2 Voltage Regulator Enable Pin
The regulator enable pin VREG_ENA is used to enable WT32. VREG_ENA enables the on-chip
switched mode regulator.
VREG_ENA is active high, with a logic threshold of around 1V, and it has weak pull-down. It can
tolerate voltages up to 4.9V, so it may be connected directly to a battery to enable the device.
VREG_ENA can be configured with iWRAP to either latch on/off the internal regulators at the rising
edge of the input voltage, or to latch the regulators on at the rising edge and shut down the regulators at
the falling edge. Following figure shows an example of how to to implement a power on/off button using
the latch feature. See iWRAP user guide for the details on configuration.