MAX4378HASD-T Maxim Integrated, MAX4378HASD-T Datasheet - Page 7

• Manufacturer Part Number: MAX4378HASD-T
• Description: Special Purpose Amplifiers
• Manufacturer: Maxim Integrated
• Series: MAX4376, MAX4377, MAX4378r

Specifications of MAX4378HASD-T

• Number Of Channels: Quad
• Common Mode Rejection Ratio (min): 90 dB
• Operating Supply Voltage: 28 V
• Supply Current: 4 mA
• Maximum Power Dissipation: 667 mW
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Available Set Gain: 33.98 dB
• Input Voltage Range (max): 28 V

The MAX4376/MAX4377/MAX4378 high-side current-
sense amplifiers feature a 0 to +28V input common-mode
range that is independent of supply voltage. This feature
allows the monitoring of current out of a battery in deep
discharge and also enables high-side current sensing at
voltages greater than the supply voltage (V
The MAX4376/MAX4377/MAX4378 operate as follows:
current from the source flows through R
load (Figure 1). Since the internal sense amplifier’s
inverting input has high impedance, negligible current
flows through RG2 (neglecting the input bias current).
Therefore, the sense amplifier’s inverting-input voltage
equals V
The amplifier’s open-loop gain forces its noninverting
input to the same voltage as the inverting input.
Therefore, the drop across RG1 equals (I
(R
(I
plies I
I
Therefore:
where amp gain is 2, 5, or 10.
The part’s gain equals (β x RGD / RG1) x amp gain.
Therefore:
where GAIN = 20 for MAX437_T.
GAIN = 50 for MAX437_F.
GAIN = 100 for MAX437_H.
Set the full-scale output range by selecting R
the appropriate gain version of the MAX4376/
MAX4377/MAX4378.
Maxim Integrated
RG1
LOAD
V
SENSE
OUT
. Solving I
RG1
)(R
= β x (RGD/RG1)(R
SOURCE
). Since I
SENSE
by a current gain factor, β, to give I
V
Single/Dual/Quad, High-Side Current-Sense
OUT
)/RG1. The internal current mirror multi-
RGD
- (I
= (GAIN)(R
RG1
LOAD
Detailed Description
= β x (I
flows through RG1, I
)(R
SENSE
SENSE
SENSE
LOAD
x I
).
)(I
LOAD
LOAD
)(R
CC
SENSE
) x amp gain
SENSE
)
).
MAX4376/MAX4377/MAX4378
SENSE
RGD
Amplifiers with Internal Gain
)/RG1.
LOAD
RG1
to the
= β x
and
=
)
The MAX4376/MAX4377/MAX4378 sense a wide variety
of currents with different sense resistor values. Table 1
lists common resistor values for typical operation of the
MAX4376/MAX4377/MAX4378.
To measure lower currents more accurately, use a high
value for R
sense voltage that reduces offset voltage errors of the
internal op amp.
In applications monitoring very high currents, R
must be able to dissipate the I
rated power dissipation is exceeded, its value may drift
or it may fail altogether, causing a differential voltage
across the terminals in excess of the absolute maxi-
mum ratings.
If I
mize the inductance of R
have the highest inductance, metal-film resistors are
somewhat better, and low-inductance metal-film resis-
tors are best suited for these applications.
Systems such as laptop computers and other devices
that have internal charge circuitry require a precise
bidirectional current-sense amplifier to monitor accu-
rately the battery’s current regardless of polarity. Figure
2 shows the MAX4377 used as a bidirectional current
monitor. This is useful for implementing either smart
battery packs or fuel gauges.
Figure 3 shows a block diagram using the MAX4376
with a switching regulator to make a current source.
SENSE
Bidirectional Current-Sense Amplifier
has a large high-frequency component, mini-
Recommended Component Values
SENSE
Applications Information
. The high value develops a higher
SENSE
Current Source Circuit
2
R losses. If the resistor’s
. Wire-wound resistors
Choosing R
SENSE
SENSE
7