11

Definitions

Gain

Gain is defined as the slope of the best-fit line of differ-

offset error adjusted out.

Nonlinearity

Nonlinearity is defined as half of the peak-to-peak output

deviation from the best-fit gain line, expressed as a per-

centage of the full-scale differential output voltage.

tied together and the signal applied to both inputs with

respect to pin GND1), expressed in dB.

Common Mode Transient Immunity, CMTI, also known as

Common Mode Rejection

CMTI is tested by applying an exponentially rising/falling

voltage step on pin 4 (GND1) with respect to pin 5 (GND2).

The rise time of the test waveform is set to approximately

50 ns. The amplitude of the step is adjusted until the dif-

mV deviation from the average output voltage for more

than 1

Ps. The ACPL-790B/790A/7900 will continue to

function if more than 10 kV/

Ps common mode slopes are

applied, as long as the breakdown voltage limitations are

observed.

Power Supply Rejection, PSR

PSR is the ratio of differential amplitude of the ripple

outputs over power supply ripple voltage, referred to the

input, expressed in dB.

Application Information

Application Circuit

The typical application circuit is shown in Figure 21. A

floating power supply (which in many applications could

be the same supply that is used to drive the high-side

power transistor) is regulated to 5 V using a simple three-

terminal voltage regulator (U1). The voltage from the

the input of the ACPL-790B/790A/7900 through an RC

anti-aliasing filter (R5 and C3). And finally, the differential

output of the isolation amplifier is converted to a ground-

referenced single-ended output voltage with a simple dif-

ferential amplifier circuit (U3 and associated components).

Although the application circuit is relatively simple, a few

recommendations should be followed to ensure optimal

performance.

0.1

PF

8

7

6

1

3

U2

5

2

4

R1

2.00 K

+15 V

C8

0.1

PF

0.1

PF

-15 V

–

+

TL032A

R3

10.0 K

ACPL-790B/

ACPL-790A/

ACPL-7900

C4

R4

10.0 K

C6

68 pF

U3

U1

78L05

IN

OUT

C1

C2

47 nF

R5

10

GATE DRIVE

CIRCUIT

POSITIVE

FLOATING

SUPPLY

HV+

* * *

HV-

–

+

MOTOR

C5

68 pF

0.1

PF

0.1

PF

C3

C7

R2

2.00 K

* * *

* * *

GND1

GND2

GND2

GND2

GND2

Figure 21. Typical application circuit for motor phase current sensing.