10

LT1787/LT1787HV

Figure 8. Unidirectional Current Sensing Mode

Figure 7. Single Supply 2.5V Bidirectional Operation

with External Voltage Reference and I/V Converter

2.5V

C1

1

µF

TO

CHARGER/

LOAD

1M

5%

1787 F07

LT1495

C3

1000pF

LT1389-1.25

2.5V

+

–

A1

1

2

3

4

8

7

6

5

LT1787

–

+

DNC

1787 F08

C

0.1

µF

2.5V TO

60V

TO

LOAD

1

2

3

4

8

7

6

5

LT1787HV

–

+

DNC

S

0

0.30

0.25

0.20

0.15

0.10

0.05

0

0.005 0.010

IDEAL

0.015 0.020

1787 F09

0.025 0.030

Figure 9. Expanded Scale of Unidirectional Output

Buffered Output Operation

Figure 7 shows the LT1787’s outputs buffered by an

operational amplifier configured as an I/V converter. This

configuration is ideal for monitoring very low voltage

reference voltage appearing at the op amp’s noninverting

The op amp’s output may swing from ground to its

positive supply voltage. The low impedance output of the

op amp may drive following circuitry more effectively than

the high output impedance of the LT1787. The I/V con-

verter configuration also works well with split supply

voltages.

Single Supply Unidirectional Operation

Figure 8 shows the simplest connection in which the

sense current. The LT1787’s outputs can swing as low as

30mV as shown in Figure 9. Accuracy is sacrificed at small

output levels, but this is not a limitation in protection

circuit applications or where sensed currents do not vary

greatly. Increased low level accuracy can be obtained by

be done with resistor dividers, voltage references or a

simple diode. Accuracy is ensured if the output signal is