LTC6102 datasheet(14/20 Pages) LINER

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LTC6102/LTC6102HV

6102fb

Figure 7. Voltage Level-Shift Circuit

Figure 8. Schottky Prevents Damage During Supply Reversal

APPLICATIONS INFORMATION

Again, very large voltages may be sensed as long as RIN

is chosen so that IOUT does not exceed the allowed output

current. For example, VIN may be as large as 1V with RIN =

1k, or as large as 10V with RIN = 10k. For a 10V maximum

input and a 5V maximum output, RIN = 10k and ROUT = 5k

will allow the LTC6102HV to translate VIN to VOUT with a

common mode voltage of up to 100V. For the case where

a large input resistor is used, a similar resistor in series

with +IN will reduce error due to input bias current.

Reverse Supply Current

Some applications may be tested with reverse-polarity

supplies due to an expectation of this type of fault during

operation. The LTC6102 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 8). This will

limit the reverse current through the LTC6102. Note that

this diode will limit the low voltage performance of the

LTC6102 by effectively reducing the supply voltage to the

part by VD.

Because the voltage across RSENSE is not restricted to

the sense range of the LTC6102 in this circuit, VSENSE

can be large compared to the allowed sense voltage. This

facilitates the sensing of very large voltages, provided

that RIN is chosen so that VSENSE/RIN does not exceed

the allowed output current. The gain is still controlled by

ROUT/RIN, so either gain or attenuation may be applied to

the input signal as it is translated to the output. Finally,

the input may be a voltage source rather than a sense

resistor, as shown in Figure 7. This circuit allows the

translation of a wide variety of input signals across the

entire supply range of the LTC6102 with only a tiny offset

error while retaining simple gain control set by ROUT/RIN.

Figure 6. LTC6102 Supply Current Monitored with Load

–INF

–INS

LTC6102

ROUT

VOUT

6102 F06

RIN

LOAD

VBAT

RSENSE

V+

V–

OUT

+IN

VREG

0.1μF

–INF

–INS

LTC6102

ROUT

VOUT

6102 F07

RIN

VIN

VCM

V+

V–

OUT

+IN

VREG

0.1μF

VOUT = VIN •

ROUT

RIN

6102 F08

LTC6102

4.99k

100

VBATT

RSENSE

–

V+

V–

–INF

OUT

–INS

+IN

VREG

0.1μF

In addition, if the output of the LTC6102 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 LTC6102’s output should be connected through

a resistor or Schottky diode (Figure 9).

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