LTC6104 datasheet(13/16 Pages) LINER

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LTC6104

6104f

Reverse Supply Protection

Some applications may be tested with reverse-polarity

supplies due to an expectation of this type of fault during

operation. The LTC6104 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 6). This will limit the

reverse current through the LTC6104. Note that this diode

will limit the low voltage performance of the LTC6104 by

effectively reducing the supply voltage to the part by VD.

Keep this in mind when choosing an output resistor and

voltage reference.

In addition, if the output of the LTC6104 is wired to a

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

through an ESD protection clamp) during a reverse sup-

ply condition, the LTC6104’s output should be connected

through a resistor or Schottky diode (Figure 7).

Response Time

The LTC6104 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.

For unidirectional applications, if the output current is

very low and an input transient occurs, there may be an

increased delay before the output voltage starts to change.

This can be improved by increasing the minimum output

current, either by increasing RSENSE or by decreasing RIN.

The effect of increased output current is illustrated in the

step response curves in the Typical Performance Charac-

teristics section of this datasheet. Note that the curves are

labeled with respect to the initial output currents.

For bidirectional applications, there is a delay when output

current changes polarity. The delay time can be found

in the step response curves in the Typical Performance

Characteristics section of this data sheet.

Speed is also affected by the external circuit. In this case,

if the input changes very quickly, the internal ampliﬁer

and the internal output FET (Figure 1) will attempt to

maintain the internal loop, but may be slew rate limited.

This results in current ﬂowing through RIN and the internal

FET. This current slew rate will be determined by the ampli-

ﬁer and FET characteristics as well as the input resistor,

RIN. Using 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

APPLICATIONS INFORMATION

Figure 6. Schottky Prevents Damage During Supply Reversal

Figure 7. Additional Resistor R1 Protects Output

During Supply Reversal

–

+INA

OUT

–

LTC6104

–INA

–INB

RIN

CHARGER/LOAD

RSENSE

VSENSE +

–

+INB

V–

ILOAD

CURRENT

MIRROR

–

ROUT

VREF

6104 F06

VOUT

–

+INA

OUT

LTC6104

–INA

–INB

RIN

CHARGER/LOAD

RSENSE

VSENSE +

–

+INB

V–

ILOAD

CURRENT

MIRROR

–

ROUT

VREF

6104 F07

–

ADC

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