LTC6102HVCDD(RevB) データシートの表示（PDF） - Linear Technology

部品番号

コンポーネント説明

メーカー

LTC6102HVCDD
(Rev.:RevB)

Precision Zero Drift Current Sense Amplifier

Linear Technology 

LTC6102/LTC6102HV

APPLICATIONS INFORMATION

Selection of External Input Resistor, RIN

The external input resistor, RIN, controls the transconduc-

tance of the current sense circuit, IOUT = VSENSE/RIN. For

example, if RIN = 100, then IOUT = VSENSE/100 or IOUT =

1mA for VSENSE = 100mV.

V+

TIE AS CLOSE TO RIN AS POSSIBLE

RSENSE

RIN–

+IN

RIN+

LOAD

V–

+–

–INS

–INF

V+

VREG

0.1μF

another way, such as with a Schottky diode across RSENSE

(Figure 3). This will reduce the high current measurement

accuracy by limiting the result, while increasing the low

current measurement resolution. This approach can be

helpful in cases where occasional large burst currents

may be ignored.

Care should be taken when designing the PC board lay-

out for RIN, especially for small RIN values. All trace and

interconnect impedances will increase the effective RIN

value, causing a gain error. It is important to note that the

large temperature drift of copper resistance will cause a

change in gain over temperature if proper care is not taken

to reduce this effect.

V+

LTC6102

OUT

VOUT

ROUT

RSENSE*

V+

LOAD

RIN–

RIN+

OUTPUT

ROUT

V–

LTC6102

CREG

V–

*VISHAY VCS1625 SERIES

WITH 4 PAD KELVIN CONNECTION

6102 F02

Figure 2. Kelvin Input Connection Preserves Accuracy

with Large Load Current and Large Output Current

RIN should be chosen to provide the required resolution

while limiting the output current. At low supply voltage,

IOUT may be as much as 1mA. By setting RIN such that

the largest expected sense voltage gives IOUT = 1mA, then

the maximum output dynamic range is available. Output

dynamic range is limited by both the maximum allowed

output current (Note 1) and the maximum allowed output

voltage, as well as the minimum practical output signal. If

less dynamic range is required, then RIN can be increased

accordingly, reducing the output current and power dis-

sipation. If small sense currents must be resolved ac-

curately in a system that has very wide dynamic range, a

smaller RIN may be used if the max current is limited in

10

RSENSE

DSENSE

6102 F03

LOAD

Figure 3. Shunt Diode Limits Maximum Input Voltage to Allow

Better Low Input Resolution Without Overranging

To further limit the effect of trace resistance on gain,

maximizing the accuracy of these circuits, the LTC6102 has

been designed with a Kelvin input. The inverting terminal

(–INS) is separate from the feedback path (–INF). During

operation, these two pins must be connected together.

The design of the LTC6102 is such that current into –INS

is input bias current only, which is typically 60pA at 25°C.

Almost all of the current from RIN flows into –INF, through

the LTC6102, and into ROUT via the OUT pin. In order to

minimize gain error, –INS should be routed in a separate

path from –INF to a point as close to RIN as possible. In

addition, the higher potential terminal of RIN should be

connected directly to the positive terminal of RSENSE (or

any input voltage source). For the highest accuracy, RIN

should be a four-terminal resistor if it is less than 10Ω.

Selection of External Output Resistor, ROUT

The output resistor, ROUT, determines how the output cur-

rent is converted to voltage. VOUT is simply IOUT • ROUT.

In choosing an output resistor, the max output voltage

must first be considered. If the circuit that is driven by the

output does not have a limited input voltage, then ROUT

6102fb

Share Link: