FS9952_LP1

Rev. 2.0

20/31

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.

Oscillation Circuit

U1

35 XOUT

34 XIN

CX1

CX2

FS9952

R1

Diagram 9

Oscillation Circuit

The oscillation of FS9952_LP1 can be quartz, but for the cost reduction, it also can be ceramic.

In the diagram, R1 is the reviser to provide the static working point; CX2 is the fine adjustment of frequency;

CX1 is temperature offset. In less requirements situation, CX1 and CX2 can be unused.

15.5 Mode Switch and Function Control Circuit

R10

180

L1

LED

S6

S5

S4

S3

S2

S11

S10

S9

S8

S7

S1

C5

0.1uF

R6

100k

VDD

27 BLOUT

16 MAXH

18 SELECT

19 RANGE

20 HOLD

26 BLCTR

21 MEA4

22 MEA3

23 MEA2

24 MEA1

25 MEA0

56 RST

FS9952

Diagram 10 Mode Switch and Function Control Circuit

S2〜S6 are mode switches which are the lock switches. For their functions, please refer to 9.1.

S1 and S7〜S11 are function control switches which are the trigger switches. For their functions, please

refer to )Keys Definition) and )Other Functions).