C8051F960-B-GM Datasheet, PDF (272/492 Pages) Silicon Laboratories – Ultra Low Power 128K, LCD MCU Family

C8051F96x
20.7. Bypass Mode
The dc-dc converter has a bypass switch (MBYP), see Figure 20.1, which allows the output voltage (VDC)
to be directly tied to the input supply (VBATDC), bypassing the dc-dc converter. The bypass switch may be
used independently from the dc-dc converter. For example, applications that need to power the VDC sup-
ply in the lowest power Sleep mode can turn on the bypass switch prior to turning off the dc-dc converter in
order to avoid powering down the external circuitry connected to VDC.
There are two ways to close the bypass switch. Using the first method, Forced Bypass Mode, the FORBYP
bit is set to a logic 1 forcing the bypass switch to close. Clearing the FORBYP bit to logic 0 will allow the
switch to open if it is not being held closed using Automatic Bypass Mode.
The Automatic Bypass Mode, enabled by setting the AUTOBYP to logic 1, closes the bypass switch when
the difference between VBATDC and the programmed output voltage is less than approximately 0.4 V.
Once the difference exceeds approximately 0.5 V, the bypass switch is opened unless being held closed
by Forced Bypass Mode. In most systems, Automatic Bypass Mode will be left enabled, and the Forced
Bypass Mode will be used to close the switch as needed by the system.
20.8. DC-DC Converter Register Descriptions
The SFRs used to configure the dc-dc converter are described in the following register descriptions.
272
Rev. 1.0