LT2940CMS datasheet(11/24 Pages) LINER

11 / 24 page

LT2940

2940f

Table 1. LT2940 Essential Operating Parameters to Achieve Speciﬁed Accuracy (VCC Operating Range = 6V to 80V)

PARA-

METER

SENSE

INPUT

PINS

PIN VOLTAGE

LIMIT

INPUT

OPERATING

RANGE

SCALING

OUTPUT

MONITOR

OUTPUT

PINS

OUTPUT

OPERATING

RANGE

OUTPUT

VOLTAGE COMPLIANCE

Voltage

V+, V–

0V to VCC – 3V at VCC ≤ 12V

0V TO 9V at 12V < VCC < 30V

0V to 18V at VCC ≥ 30V

VV = ±8V

Current

I+, I–

4V to 80V*

VI = ±200mV

GIMON =

1000μA /V

IMON

IIMON =

±200μA

Sourcing:

0V to VCC – 4.5V at VCC ≤ 7.5V

0V to 7.5V at 12V < VCC < 30V

0V to 12V at VCC ≥ 30V

Sinking:

As Above, Except Minimum is 0.5V

Power

V+, V–,

I+, I–

See Above Limits

VV • VI = ±0.4V2

KPMON =

500μA / V2

PMON

IPMON =

±200μA

* The current sense range is completely independent of the supply voltage.

APPLICATIONS INFORMATION

PMON and IMON outputs are capable of indicating forward

and reverse ﬂow of power and current, provided they are

advantageously biased.

The multiplier core full-scale product of ±0.4V2 may

be reached over a range of voltage and current inputs,

as shown in Figure 2. For example, voltage sense and

current sense combinations of 8V and 50mV, 4V and

100mV, and 2V and 200mV each multiply to 0.4V2, and

thus produce 200μA at PMON. This arrangement allows

the core to operate at full-scale, and therefore at best ac-

curacy, over a 4:1 range of current and voltage, a readily

appreciated feature when monitoring power in variable

supply applications.

Essential Design Equations

A few equations are needed to calculate input scaling factors

and achieve a desired output. Consider the basic applica-

tion in Figure 3, where the power PIN is to be measured

as the product of voltage VIN and current IIN:

PIN = VIN • IIN

(6)

The actual measured quantities VIN and IIN are scaled to be

level-compatible with the LT2940. In this basic application,

a simple resistive voltage divider scales VIN, and a sense

resistor scales IIN.

VV = VIN • kV

(7a)

V =

(7b)

VI = IIN • kI

(8a)

kI = RSENSE

(8b)

The PMON output current is given by:

IPMON = KPMON • VIN • kV • IIN • kI

(9a)

IPMON = PIN • KPMON • kV • kI

(9b)

The output current may be positive (sourcing) or

negative (sinking) depending on the signs of VIN, kV,

IIN, and kI. Provided that the magnitudes of VV and VI

do not exceed 8V and 200mV as shown in Figure 2, at

Figure 2. PMON Output Current as a Function

of Sense Input Voltages

2940 F02

VV = VV+ – VV– (V)

100

12.5

200

0.5

IPMON

= 200μA

25μA

50μA

100μA

12.5μA

LT2940CMS датащи(PDF) 11 Page - Linear Technology

LT2940CMS датащи(HTML) 11 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

датащи скачать

ссылки URL