LTC6102 datasheet(13/20 Pages) LINER

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LTC6102/LTC6102HV

6102fb

The LTC6102HV can be used at voltages up to 105V. This

additional voltage requires that more power be dissipated

for a given level of current. This will further limit the allowed

output current at high ambient temperatures.

It is important to note that the LTC6102 has been designed

to provide at least 1mA to the output when required, and

can deliver more depending on the conditions. Care must

be taken to limit the maximum output current by proper

choice of sense and input resistors and, if input fault

conditions are likely, an external clamp.

Output Filtering

The output voltage, VOUT, is simply IOUT • ZOUT. This

makes ﬁltering straightforward. Any circuit may be used

which generates the required ZOUT to get the desired ﬁlter

response. For example, a capacitor in parallel with ROUT

will give a low pass response. This will reduce unwanted

noise from the output, and may also be useful as a charge

reservoir to keep the output steady while driving a switch-

ing circuit such as a mux or ADC. This output capacitor

in parallel with an output resistor will create a pole in the

output response at:

f–3dB =

2• •ROUT •COUT

Useful Equations

Input Voltage: VSENSE =ISENSE •RSENSE

Voltage Gain:

VOUT

VSENSE

ROUT

RIN

Current Gain:

IOUT

ISENSE

RSENSE

RIN

Transconductance:

IOUT

VSENSE

RIN

Transimpedance:

VOUT

ISENSE

SENSE •

ROUT

RIN

APPLICATIONS INFORMATION

Figure 5. V+ Powered Separately from Load Supply (VBAT)

6102 F05

LTC6102

ROUT

VOUT

RIN

VBAT

LOAD

(V+ – 2V) TO V+

RSENSE

V+

V–

OUT

+IN

V+

–INF

–INS

VREG

0.1μF

Input Sense Range

The inputs of the LTC6102 can function from V+ to (V+ – 2V).

Not only does this allow a wide VSENSE range, it also allows

the input reference to be separate from the positive supply

(Figure 5). Note that the difference between VBAT and V+

must be no more than the input sense voltage range listed

in the Electrical Characteristics table.

Monitoring Voltages Above V+ and Level Translation

The LTC6102 may be conﬁgured to monitor voltages that are

higher than its supply, provided that the negative terminal

of the input voltage is within the input sense range of the

LTC6102. Figure 6 illustrates a circuit in which the LTC6102

has its supply pin tied to the lower potential terminal of the

sense resistor instead of the higher potential terminal. The

operation of the LTC6102 is such that the –INS and –INF

pins will servo to within a few microvolts of +IN, which is

shorted to V+. Since the input sense range of the LTC6102

includes V+, the circuit will operate properly. The voltage

across RSENSE will be held across RIN by the LTC6102,

causing current VSENSE/RIN to ﬂow to ROUT. In this case,

the supply current of the LTC6102 is also monitored, as

it ﬂows through RSENSE.

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