LTC1921 datasheet(15/22 Pages) LINER

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LTC6101/LTC6101HV

6101fh

APPLICATIONS INFORMATION

Reverse Supply Protection

Some applications may be tested with reverse-polarity

supplies due to an expectation of this type of fault during

operation. The LTC6101 is not protected internally from

external reversal of supply polarity. To prevent damage that

may occur during this condition, a Schottky diode should

be added in series with V– (Figure 7). This will limit the

reverse current through the LTC6101. Note that this diode

will limit the low voltage performance of the LTC6101 by

effectively reducing the supply voltage to the part by VD.

In addition, if the output of the LTC6101 is wired to a device

that will effectively short it to high voltage (such as through

an ESD protection clamp) during a reverse supply condi-

tion, the LTC6101’s output should be connected through

a resistor or Schottky diode (Figure 8).

Response Time

The LTC6101 is designed to exhibit fast response to inputs

for the purpose of circuit protection or signal transmission.

This response time will be affected by the external circuit

in two ways, delay and speed.

If the output current is very low and an input transient

occurs, there may be an increased delay before the output

voltage begins changing. This can be improved by increas-

ing the minimum output current, either by increasing

RSENSE or decreasing RIN. The effect of increased output

current is illustrated in the step response curves in the

Typical Performance Characteristics section of this data

sheet. Note that the curves are labeled with respect to the

initial output currents.

The speed is also affected by the external circuit. In this

case, if the input changes very quickly, the internal ampli-

ﬁer will slew the gate of the internal output FET (Figure

1) in order to maintain the internal loop. This results in

current ﬂowing through RIN and the internal FET. This

current slew rate will be determined by the ampliﬁer and

FET characteristics as well as the input resistor, RIN. Us-

ing a smaller RIN will allow the output current to increase

more quickly, decreasing the response time at the output.

This will also have the effect of increasing the maximum

output current. Using a larger ROUT will decrease the re-

sponse time, since VOUT = IOUT • ROUT. Reducing RIN and

increasing ROUT will both have the effect of increasing the

voltage gain of the circuit.

Figure 7. Schottky Prevents Damage During Supply Reversal

Figure 8. Additional Resistor R3 Protects

Output During Supply Reversal

6101 F07

LTC6101

4.99k

100

VBATT

RSENSE

–

V+

V–

OUT

–IN

+IN

6101 F08

ADC

LTC6101

4.99k

100

VBATT

RSENSE

–

V+

V–

OUT

–IN

+IN

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