FS9721_LP1 datasheet(30/41 Pages) FORTUNE

30 / 41 page

FS9721_LP1

Rev. 2.0

31/41

R17

R16

0.99

R29

0.01

uA/mA

0.5A/250V

10A

10A/250V

J11

J10

COM

ADPC1

SGND

FS9721_LP1

R18

90k

10k

OP1O

OP1N

Diagram 27

Current Measurement(B)

In TSTB connecting to VSS mode, the current signal enters IC from SA.

When doing the current measurement, The sampling resistance of μA mode is R16+R17+R29,

the sampling resistance of mA mode is R16+R29, and the sampling resistance of 10A mode is R29.

They are measured respectively through the mode switch. When measuring μA, J10 is open and

J11 is close; when measuring mA, J11 is open and J10 is close; the large current enters directly via

10A port.

The maximum reduced voltage for μA, mA and 10A modes is 0.4V.

These voltages are input voltage comparator to compare. If the voltage is smaller than 40mV, it

will be sent to ×10 times ampifier to amplify, then sent to A/D converter; if the voltage is larger than

40mV, the system will work the auto-ranging signal, and jump up one mode under the control of

microprocessor and send the current signal directly to the A/D converter.

The accuracy of resistance R16, R17, R29, R8 and R9 affects the accuracy of the current

measurement.

FS9721_LP1 데이터시트(PDF) 30 Page - Fortune Semiconductor Corp.