MAX4073F Maxim, MAX4073F Datasheet - Page 7

• 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

The MAX4073 high-side current-sense amplifier fea-
tures a +2V to +28V input common-mode range that is
independent of supply voltage. This feature allows the
monitoring of current out of a battery as low as +2V and
also enables high-side current sensing at voltages
greater than the supply voltage (V
The MAX4073 operates as follows: current from the
source flows through R
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
gain forces its noninverting input to the same voltage as
the inverting input. Therefore, the drop across RG1
equals (I
I
multiplies I
I
RG1. Assuming infinite output impedance, V
(RGD). Substituting in for I
β
β
(I
50V/V for MAX4073F, and GAIN = 100V/V for MAX4073H.
Set the full-scale output range by selecting R
the appropriate gain version of the MAX4073.
The MAX4073 senses a wide variety of currents with
different sense resistor values. Table 1 lists common
resistor values for typical operation of the MAX4073.
To measure lower currents more accurately, use a
large value for R
RG1
RGD
SOURCE
LOAD
✕
✕
SOT23-6
(RGD / RG1)(R
RGD / RG1. Therefore, V
1, 2
= (I
= β
3
4
5
6
), where GAIN = 20V/V for MAX4073T, GAIN =
LOAD
LOAD
✕
- (I
Recommended Component Values
PIN
RG1
I
RG1
LOAD
)(R
)(R
Applications Information
SENSE
. Solving I
SC70-5
SENSE
by a current gain factor, β, to give
SENSE
SENSE
_______________________________________________________________________________________
)(R
2
3
4
5
1
SENSE
SENSE
) / RG1. The internal current mirror
). Since I
Detailed Description
. The larger value develops a
✕
RGD
RGD
I
LOAD
). The amplifier’s open-loop
to the load (Figure 1). Since
NAME
OUT
and rearranging, V
GND
OUT
RS+
V
= β
RS-
RG1
). The parts gain equals
CC
Choosing R
High-Side Current-Sense Amplifier
CC
= (GAIN) (R
✕
flows through RG1,
Low-Cost, SC70, Voltage-Output,
).
(I
LOAD
Ground
Supply Voltage Input. Bypass to GND with a 0.1µF capacitor.
Power-Side Connection to the External Sense Resistor
Load-Side Connection to the External Sense Resistor
Voltage Output. V
12kΩ.
OUT
)(R
SENSE
SENSE
SENSE
= (I
SENSE
OUT
RGD
and
) /
=
)
)
OUT
is proportional to V
higher-sense voltage that reduces offset voltage errors
of the internal op amp. Typical sense voltages range
between 10mV and 150mV.
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 (±5V).
If I
mize the inductance of R
have the highest inductance, metal-film resistors are
Figure 1. Functional Diagram
SENSE
+3V TO +28V
V
+2V TO +28V
SOURCE
has a large high-frequency component, mini-
FUNCTION
SENSE
V
CC
GND
CURRENT
MIRROR
. Output impedance is approximately
I
RG1
R
RS+
RGD = 12kΩ
G1
SENSE
MAX4073T/F/H
R
SENSE
A1
2
I
RGD
Pin Description
R losses. If the resistor’s
. Wire-wound resistors
OUT
R
RS-
I
LOAD
G2
TO LOAD/BATTERY
V
OUT
SENSE
7