Datasheet

FS98O22
Rev. 1.6 29/146
4. Power System
FS98O22 has a special power system that can supply a fixed voltage (3.6V) for CPU and ADC. FS98O22 could
work when the supply voltage is within a specified range, fixed or floating. The power system has 6 function
engines as Voltage Doubler, Voltage Regulator, Analog Bias Circuit, Common Voltage Generator Low
Battery Comparator and Band gap Voltage / Temperature Sensor. Through the first 4 function engines, the
system can generate 3 Voltage level as VGG = 2VDDP, VDDA = 3.6V, AGND = 1.8V. Please see Figure 4-1.
1. Voltage Doubler
The acceptable VDD range for FS98O22 is from 2.2V to 3.6V. Voltage Doubler raises the voltage of VGG
to 2 times of VDDP
3
. VGG is used as the input of Voltage Regulator. It is from 4.4V to 7.2V. Please see
Section 4.1 for detailed register setting.
2. Voltage Regulator
The fixed voltage is important when the Analog function is working. Voltage Regulator raises the voltage
of VDDA to fixed 3.6V. Although the input voltage of Voltage Regulator, VGG, is from 4.4V to 7.2V (It
depends on the voltage of VDD), the minimum possible voltage is still higher than 3.6V, so Voltage
Regulator could surely supply VDDA as 3.6V. Please refer to Section 4.2 for detailed register setting.
3. Analog Bias Circuit
Analog Bias Circuit is used to set VB to 3.6V. VB is used for FS98O22 Analog Function Network. The
user needs to enable Analog Bias Circuit, and then the Analog Functions such as ADC or OPAMP can
work correctly. Please refer to Section 4.3 for detailed register setting.
4. Common Voltage Generator
FS98O22 sets the analog ground to half VDDA. Please refer to Section 4.4 for detailed register setting.
Figure 4-1 FS98O22 power system block
3
VDDP means the VDD for Charge Pump (Voltage Doubler). User usually connects the VDDP to VDD.
VSSP means the VSS for Charge Pump (Voltage Doubler). User usually connects the VSSP to VSS.
FORTUNE'
Properties
For Reference Only