MAX4073 Просмотр технического описания (PDF) - Maxim Integrated

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MAX4073

Low-Cost, SC70, Voltage-Output, High-Side Current-Sense Amplifier

Maxim Integrated 

MAX4073T/F/H

Low-Cost, SC70, Voltage-Output,

High-Side Current-Sense Amplifier

somewhat better, and low-inductance metal-film resis-

tors are best suited for these applications.

For VSENSE = 100mV, full-scale output voltage can be

2V, 5V, or 10V depending on the gain. For proper oper-

ation, ensure VCC exceeds the full-scale output voltage

by 1.2V (see Output High Voltage (VCC - VOH) vs.

Temperature in the Typical Operating Characteristics).

Using a PCB Trace as RSENSE

If the cost of RSENSE is an issue and accuracy is not

critical, use the alternative solution shown in Figure 2.

This solution uses copper PC board traces to create a

sense resistor. The resistivity of a 0.1-inch-wide trace of

2-ounce copper is approximately 30mΩ/ft. The resis-

tance-temperature coefficient of copper is fairly high

(approximately 0.4%/°C), so systems that experience a

wide temperature variance must compensate for this

effect. In addition, do not exceed the maximum power

dissipation of the copper trace.

For example, the MAX4073T (with a maximum load cur-

rent of 10A and an RSENSE of 5mΩ) creates a full-scale

VSENSE of 50mV that yields a maximum VOUT of 1V.

RSENSE in this case requires about 2 inches of 0.1 inch-

wide copper trace.

Output Impedance

The output of the MAX4073 is a current source driving a

12kΩ resistance. Resistive loading added to OUT

reduces the output gain of the MAX4073. To minimize

output errors for most applications, connect OUT to a

high-impedance input stage. When output buffering is

required, choose an op amp with a common-mode

input range and an output voltage swing that includes

ground when operating with a single supply. The op

amp’s supply voltage range should be at least as high

as any voltage the system may encounter.

The percent error introduced by output loading is deter-

mined with the following formula:

%ERROR

=

100

⎛ RLOAD

⎝⎜ 12kΩ + RLOAD

− 1⎞⎠⎟

where RLOAD is the external load applied to OUT.

INPUT

0.3in COPPER

RSENSE

+ 0.1in COPPER _

VSENSE

RS+

RS-

VCC

MAX4073T

LOAD/BATTERY

0.3in COPPER

+3V TO +28V

0.1µF

OUT

GND

Figure 2. MAX4073T Connections Showing Use of PC Board

VIN LOW-COST +2V TO +28V

SWITCHING

REGULATOR

VSENSE

RSENSE

+3V TO +28V

0.1µF

RS+

RS-

VCC

MAX4073T/F/H

ILOAD

OUT

GND

LOAD/

BATTERY

Figure 3. Current Source

Current Source Circuit

Figure 3 shows a block diagram using the MAX4073

with a switching regulator to make a current source.

8

Maxim Integrated

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