MAX9922 Maxim, MAX9922 Datasheet - Page 10

• Manufacturer Part Number: MAX9922
• Description: The MAX9922/MAX9923 ultra-precision, high-side current-sense amplifiers feature ultra-low offset voltage (VOS) of 25µV (max) and laser-trimmed gain accuracy better than 0
• Manufacturer: Maxim

The MAX9922/MAX9923 high-side, current-sense
amplifiers implement a spread-spectrum autozeroing
technique that minimizes the input offset error, offset
drift over time and temperature, and the effect of 1/f
noise. This technique achieves less than 25µV (max)
offset voltage.
The MAX9922/MAX9923 high-side current-sense ampli-
fiers feature a +1.9V to +28V input common-mode
range that is independent of supply voltage (V
feature allows the monitoring of current out of a battery
as low as +1.9V and enables high-side current sensing
at voltages greater than the supply voltage.
The MAX9922/MAX9923 monitor current through a cur-
rent-sense resistor and amplify the voltage across the
resistor. The 28V input common-mode voltage (V
range of the MAX9922/MAX9923 is independent of the
supply voltage (V
does not interfere with the ground path of the load
being measured, making the MAX9922/MAX9923 par-
ticularly useful in a wide range of high-voltage systems.
Ultra-Precision, High-Side
Current-Sense Amplifiers
10
GND
N.C.
RSB
RS+
RS-
______________________________________________________________________________________
1
2
3
4
5
DD
). High-side current monitoring
GAIN = 1 +
Detailed Description
MAX9922
(
R2
R1
)
DD
10
9
8
7
6
V
SHDN
). This
DD
RS+
OUT
FB
REF
R2
R1
)
GND
N.C.
RSB
RS+
RS-
The MAX9922/MAX9923 use Maxim’s indirect current
feedback achitecture. This architecture con-
verts the differential input voltage signal to a current
through an input transconductance stage. An output
transconductance stage converts a portion of the output
voltage (equal to the output voltage divided by the
gain) into another precision current. These two currents
are subtracted and the result is fed to a loop amplifier
with sufficient gain to minimize errors (see the
Functional Diagrams.)
Battery-powered systems require a precise bidirection-
al current-sense amplifier to accurately monitor the bat-
tery’s charge and discharge currents. Measurements of
OUT with respect to V
voltage during charge and discharge cycles (Figure 1).
The MAX9922 allows adjustable gain with a pair of exter-
nal resistors between OUT, FB, and REF. The MAX9923T/
MAX9923H/MAX9923F use laser-trimmed internal resis-
tors for fixed gains of 25, 100, and 250, respectively, with
0.5% gain accuracy (see the Functional Diagrams. )
1
2
3
4
5
VERSION
H
T
F
MAX9923
REF
MAX9923
Functional Diagrams
yield a positive and negative
GAIN
100
250
25
R2
R1
10
9
8
7
6
V
OUT
FB
REF
SHDN
DD