MAX4073F Maxim, MAX4073F Datasheet - Page 8

• Manufacturer Part Number: MAX4073F
• Description: The MAX4073 low-cost, high-side current-sense amplifier features a voltage output that eliminates the need for gain-setting resistors making it ideal for cell phones, notebook computers, PDAs, and other systems where current monitoring is crucial
• Manufacturer: Maxim

somewhat better, and low-inductance metal-film resis-
tors are best suited for these applications.
For V
2V, 5V, or 10V depending on the gain. For proper oper-
ation, ensure V
by 1.2V (see Output High Voltage (V
Temperature in the Typical Operating Characteristics).
If the cost of R
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 R
V
R
wide copper trace.
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:
where R
Figure 3 shows a block diagram using the MAX4073
with a switching regulator to make a current source.
Low-Cost, SC70, Voltage-Output,
High-Side Current-Sense Amplifier
8
SENSE
SENSE
_______________________________________________________________________________________
SENSE
%
ERROR
LOAD
in this case requires about 2 inches of 0.1 inch-
of 50mV that yields a maximum V
= 100mV, full-scale output voltage can be
is the external load applied to OUT.
CC
SENSE
=
Using a PCB Trace as R
exceeds the full-scale output voltage
100
SENSE
is an issue and accuracy is not



12k
Current Source Circuit
of 5mΩ) creates a full-scale
Ω +
R
LOAD
Output Impedance
R
LOAD
CC
−
OUT
1
- V



SENSE
OH
of 1V.
) vs.
Figure 2. MAX4073T Connections Showing Use of PC Board
Figure 3. Current Source
V
IN
0.3in COPPER
REGULATOR
SWITCHING
LOW-COST
INPUT
+2V TO +28V
0.1µF
+3V TO +28V
+
RS+
0.1in COPPER
MAX4073T
R
V
SENSE
SENSE
GND
OUT
RS+
V
CC
MAX4073T/F/H
RS-
V
R
V
OUT
SENSE
GND
SENSE
CC
_
RS-
+3V TO +28V
LOAD/BATTERY
0.3in COPPER
0.1µF
I
LOAD
BATTERY
LOAD/