MAX471ESA-T Maxim Integrated, MAX471ESA-T Datasheet - Page 10

• Manufacturer Part Number: MAX471ESA-T
• Description: Special Purpose Amplifiers
• Manufacturer: Maxim Integrated
• Series: MAX471, MAX472r

Specifications of MAX471ESA-T

• Number Of Channels: Single
• Operating Supply Voltage: 5 V, 9 V, 12 V, 15 V
• Supply Current: 0.05 mA
• Maximum Power Dissipation: 791 mW
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Supply Voltage - Max: 36 V
• Supply Voltage - Min: 3 V

The MAX471’s maximum sense current is 3A
power-up, fault conditions, or other infrequent events,
larger peak currents are allowed, provided they are
short—that is, within a safe operating region, as shown
in Figure 5.
Figure 5. MAX471 Pulse Current Safe Operation for 10,000
Pulses and Fuse Time for Continuous Current. Pulse tests done
with 250mW average power dissipation.
R
the MAX472. V
load/charge or power-source/battery side of the sense
resistor. Connect V
R
in the measured current.
The general circuit of Figure 4 is useful in a wide variety
of applications. It can be used for high-current applica-
tions (greater than 3A), and also for those where the full-
scale load current is less than the 3A of the MAX471.
Table 1. Suggested Component Values for the MAX472
FULL-SCALE
SENSE
SENSE
CURRENT,
I
SENSE
LOAD
0.1
10
1
5
, RG1, and RG2 are externally connected on
if you want to include the MAX472 current drain
(A)
50
45
40
35
30
25
20
15
10
5
0
T
RESISTOR,
CURRENT-
CC
A
10
DIP safe
operating region
= +25°C
R
SENSE
_______________________________________________________________________________________
(mΩ)
SENSE
500
50
10
can be connected to either the
5
CC
PULSE WIDTH (sec)
Suggested Component Values
100
to the load/charge side of
GAIN-SETTING
Small
for Various Applications
Outline
RESISTORS,
RG1 = RG2
fuse
time
Small Outline safe
operating region
Peak Sense Current
200
200
100
1m
(Ω)
50
DIP
fuse
time
10m
MAX472
RESISTOR,
RMS
OUTPUT
R
(kΩ)
OUT
10
10
. For
5
2
Current-Sense Amplifiers
FULL-SCALE
VOLTAGE,
Table 1 shows suggested component values and indi-
cates the resulting scale factors for various applications
required to sense currents from 100mA to 10A.
Higher or lower sense-current circuits can also be built.
Select components and calculate circuit errors using
the guidelines and formulas in the following section.
Choose R
a) Voltage Loss: A high R
b) Accuracy: A high R
c) Efficiency and Power Dissipation: At high current
d) Inductance: If there is a large high-frequency com-
e) Cost: If the cost of R
OUTPUT
V
OUT
power-source voltage to degrade through IR loss.
For least voltage loss, use the lowest R
currents to be measured more accurately. This is
because offsets become less significant when the
sense voltage is larger.
levels, the I
Take this into consideration when choosing the
resistor value and power dissipation (wattage) rat-
ing. Also, if the sense resistor is allowed to heat up
excessively, its value may drift.
ponent to I
low. Wire-wound resistors have the highest induc-
tance, while metal film is somewhat better. Low-
inductance metal-film resistors are available. Instead
of being spiral wrapped around a core, as in metal-
film or wire-wound resistors, these are a straight
band of metal. They are made in values under 1Ω.
may want to use an alternative solution, as shown in
Figure 6. This solution uses the PC board traces to
create a sense resistor. Because of the inaccuracies
of the copper “resistor,” you will need to adjust the
full-scale current value with a potentiometer. Also,
the resistance temperature coefficient of copper is
fairly high (approximately 0.4%/°C), so systems that
experience a wide temperature variance should take
this into account.
2.5
2.5
2.5
2
(V)
Precision, High-Side
SENSE
V
SENSE
2
OUT
FACTOR,
R losses in R
SCALE
based on the following criteria:
(V/A)
2.5
0.5
0.2
25
/I
SENSE
, you will want to keep inductance
SENSE
SENSE
SENSE
SENSE
TYPICAL ERROR AT X%
1%
14
14
13
12
becomes an issue, you
OF FULL LOAD (%)
value allows lower
value will cause the
may be significant.
10%
2.5
2.5
2.0
2.0
SENSE
R
100%
value.
SENSE
0.9
0.9
1.1
1.6
9