OPA379

OPA2379

OPA4379

SBOS347A − NOVEMBER 2005 − REVISED DECEMBER 2005

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8

In unity-gain inverter configuration, phase margin can be

reduced by the reaction between the capacitance at the op

amp input and the gain setting resistors, thus degrading

capacitive load drive. Best performance is achieved by

using smaller valued resistors. However, when large

valued resistors cannot be avoided, a small (4pF to 6pF)

in Figure 3. This configuration significantly reduces

which includes the amplifier input capacitance and PC

board parasitic capacitance.

R

I

OPA379

V

IN

V

OUT

R

F

C

FB

C

IN

C

L

Figure 3. Improving Capacitive Load Drive

BATTERY MONITORING

The low operating voltage and quiescent current of the

OPA379 series make it an excellent choice for battery

monitoring applications, as shown in Figure 4. In this

remains above 2V. A low-power reference is used to set

the trip point. Resistor values are selected as follows:

1.

is approximately 1000x larger than the maximum bias

current over temperature:

R

V

REF

1000 I

BMAX

+

1.2V

+ 12MW [ 10MW

2.

monitoring applications, 50mV is adequate.

3.

R

V

HYST

V

BATT

+ 10MW

50mV

2.4V

+ 210kW

4.

5.

R

2

+

1

V

THRS

V

REF

R

1

R

1

R

F

+

1

2V

1.2V

210k

1

210k

1

10M

W

+ 325kW

6.

circuit will be 1.8V. The REF1112 has a current

requirement of 1.2

µA (max). Providing it 2µA of supply

current assures proper operation. Therefore:

R

V

BATTMIN

I

BIAS

+ 1.8V

2

mA

+ 0.9MW

REF1112

OPA379

+IN

OUT

−IN

V

STATUS

V

BATT

V

REF

R

1

R

2

R

BIAS

I

BIAS

R

F

+

Figure 4. Battery Monitor

(1)

(2)

(3)

(4)