®

ISC300

9

Com 1

+In

–In

Undefined

–V

ISO

I

2

I

1

R

S

Output Undefined

FIGURE 13. –In and +In Open Circuit.

APPLICATIONS FLEXIBILITY

ISOLATED VOLTAGE MEASUREMENT CHANNEL

Figure 15 shows the ISC300 configured for a

±10V input.

With a few external components the ISC300 can accurately

convert a

±10V input to an isolated ±10V output with no

external adjustments. The primary function of the output

circuitry is to add gain to convert the

±5V output of the

ISC300 to

±10V, and to reduce output impedance. The

addition of a few resistors and capacitors provides an active

low pass filter with a cut off frequency of typically 200Hz.

The filter response is flat to 1dB and rolls off from cut off

at –12dB per octave.

ISOLATED MEASUREMENT BRIDGE CIRCUIT

Figure 16 shows a measurement bridge circuit using the

ISC300. All the input circuitry is powered by the ISC300

isolated supplies. The OPA1013 dual op amp is used to

Com 1

+In

–In

Undefined

–V

ISO

I

2

I

1

R

S

Output Undefined

FIGURE 14. Com 1 Open Circuit.

FIGURE 15. Isolated Voltage Measurement Channel with Output Filter.

OPA27GP

Logic

Control

6.8nF

±10V

OUT

+10V

IN

Out

ACom 2

DCom 2

+In

Sense 1

–In

Sense 2

Com 1

6.8nF

100k

Ω

100k

Ω

22k

Ω

22k

Ω

+V

CC

ƒ

+V

DD

excite the measurement bridge and the INA102 is used to

amplify the bridge delta voltage. Connecting pins 4 and 7

together, and pins 5 and 6 together on the INA102 sets its

gain to 1000.

ISOLATED 4 TO 20MA RECEIVER

In Figure 17, the ISC300 converts a 4 to 20mA current to an

isolated 0 to 5V output. The 6.25

Ω resistor converts the 4 to

20mA input to 0.025 to 0.125V. The 125

Ω resistor in

conjunction with the 200

µA current source provides an

offset of –0.025V. Fine offset and gain adjustment gives an

accurate 0 to 0.1V input range.

Offset and Gain Adjustment

16mA change on the input.