FS9721_LP3

Rev. 2.1

20/39

2*VDD

3.9V

1.2V

0.4V

1.5V

1.5V

VGG

VDDA

REFO

REFI

VDD

AGND

VSS

FS9721_LP3

RLCD

3V

Diagram 9

Relative Voltage for Each Point

VB is the IC internal bias current input. The increase of R4 will decrease IC internal current consumption, but

insufficient bias current will influence AC measurement input range.

AGND is the analog ground connection. Its potential is equal to the middle point of battery voltage. The

potential of the point is generated by IC internal voltage that cannot connect to the middle point of battery.

C4 and C5 are the bypass capacitances in one hand, and in the other hand to make AGND be regulated to

VDD and VSS. C2 is power pump capacitance. IC makes VDD go through C2 to charge/discharge so as to raise

VGG up to approximate double.

VDDA is the output voltage after regulating VGG in the IC that is about 3.9V relative to VSS.

REFO is the IC internal bandgap power that is about 1.2V relative to AGND, and has the stability of

100ppm/

.

℃

15.3

Power Supply Circuit

According to different application of users, the supply methods are different. In some measurements, all

operating amplifier, Hale components and so on sensors require larger voltage so that it is difficult to supply by

3V. If so, the following supply methods are recommended:

10uF

10uF

3V

VDD

AGND

VSS

FS9721_LP3

Diagram 10

3V Power Supply