FS9952_LP2

Power System

R7

40k

R4

20k

R2

82k

VR2

10k

C4

10μF

C3

10μF

C1

10μF

C8

10μF

C2

10μF

C14

0.1μF

3V

BT1

57 REFI

58 REFO

39 VDDA

33 VB

38 VGG

36 CA

37 CB

31 VDD

30 AGND

29 VSS

FS9952

Diagram 7 Power System

The voltages of IC pins in the power system are shown as Diagram 8.

2*VDD

3.9V

1.2V

1.5V

FS9952

0.4V

1.5V

38 VGG

39 VDDA

58 REFO

57 REFI

31 VDD

29 VSS

30 AGND

Diagram 8 Voltage of Each Point in Power System

VB is the bias current input point in IC. The increase of R4 will reduce the current consumption in IC, but the

shortage of bias current will affect the input range of AC measurement.

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

potential of the point is generated in the IC and cannot connect to the middle point of battery.

C4 and C5 are bypath capacitance, and also to make AGND regulated to VDD and VSS. C2 is the power pump

capacitance. IC makes VDD voltage pass C3 to charge/discharge so as to raise VGG to be about double

voltage of VDD.

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

REFO is the bandgap power source in the IC. It is about 1.2V that relative to AGND and has 100ppm/℃

stability.

Rev. 1.2

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