C8051F960-B-GM Datasheet, PDF (269/492 Pages) Silicon Laboratories – Ultra Low Power 128K, LCD MCU Family

C8051F96x
20. On-Chip DC-DC Buck Converter (DC0)
C8051F96x devices include an on-chip step down dc-dc converter to efficiently utilize the energy stored in
the battery, thus extending the operational life time. The dc-dc converter is a switching buck converter with
an input supply of 1.8 to 3.8 V and an output that is programmable from 1.8 to 3.5 V in steps of 0.1 V. The
battery voltage should be at least 0.4 V higher than the programmed output voltage. The programmed out-
put voltage has a default value of 1.9 V. The dc-dc converter can supply up to 250 mW. The dc-dc con-
verter can be used to power the MCU and/or external devices in the system (e.g., an RF transceiver).
The dc-dc converter has a built in voltage reference and oscillator, and will automatically limit or turn off the
switching activity in case the peak inductor current rises beyond a safe limit or the output voltage rises
above the programmed target value. This allows the dc-dc converter output to be safely overdriven by a
secondary power source (when available) in order to preserve battery life. When enabled, the dc-dc con-
verter can source current into the output capacitor, but cannot sink current. The dc-dc converter’s settings
can be modified using SFR registers described in Section 20.8.
Figure 20.1 shows a block diagram of the buck converter.
VBAT
DC/DC Converter
IND
VBATDC
4.7 uF
+ 0.1uF
+ 0.01uF
MBYP
M1
Control Logic
SFR
Control
Voltage
Reference
Local
Oscillator
0.56 uH
VDC
2.2 uF
+0.1uF
I_load
+0.01uF
GNDDC
GND
Figure 20.1. Step Down DC-DC Buck Converter Block Diagram
Rev. 1.0
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