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PDF MAX9922 Data sheet ( Hoja de datos )
| Número de pieza | MAX9922 | |
| Descripción | (MAX9922 / MAX9923) High-Side Current-Sense Amplifiers | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-4429; Rev 0; 3/09
EVAALVUAAILTAIOBNLEKIT
Ultra-Precision, High-Side
Current-Sense Amplifiers
www.datasheet4u.com
General Description
The MAX9922/MAX9923 ultra-precision, high-side cur-
rent-sense amplifiers feature ultra-low offset voltage
(VOS) of 25µV (max) and laser-trimmed gain accuracy
better than 0.5%. The combination of low VOS and high-
gain accuracy allows precise current measurements
even at very small sense voltages.
The MAX9922/MAX9923 are capable of both unidirec-
tional and bidirectional operation. For unidirectional
operation, connect REF to GND. For bidirectional oper-
ation, connect REF to VDD/2.
The MAX9922 has adjustable gain set with two external
resistors. The MAX9923T/MAX9923H/MAX9923F use an
internal laser-trimmed resistor for fixed gain of 25V/V,
100V/V, and 250V/V, respectively. The devices operate
from a +2.85V to +5.5V single supply, independent
of the input common-mode voltage, and draw only 700µA
operating supply current and less than 1µA in shutdown.
The +1.9V to +28V current-sense input common-mode
voltage range makes the MAX9922/MAX9923 ideal for
current monitoring in applications where high accuracy,
large common-mode measurement range, and mini-
mum full-scale VSENSE voltage is critical.
The MAX9922/MAX9923 use a patented spread-spec-
trum autozeroing technique that constantly measures
and cancels the input offset voltage, eliminating drift
over time and temperature, and the effect of 1/f noise.
This, in conjunction with the indirect current-feedback
technique, achieves less than 25µV (max) offset voltage.
The MAX9922/MAX9923 are available in a small 10-pin
µMAX® package and are specified over the -40°C to
+85°C extended temperature range.
Applications
Notebook/Desktop Power Management
Handheld Li+ Battery Current Monitoring
Precision Current Sources
Typical Operating Circuits appear at end of data sheet.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Features
♦ Ultra-Precision VOS Over Temperature
MAX9922: ±10µV (max)
MAX9923T: ±25µV (max)
MAX9923H: ±20µV (max)
MAX9923F: ±10µV (max)
♦ ±0.5% (max) Full-Scale Gain Accuracy
♦ Bidirectional or Unidirectional ISENSE
♦ Multiple Gains Available
Adjustable (MAX9922)
+25V/V (MAX9923T)
+100V/V (MAX9923H)
+250V/V (MAX9923F)
♦ 1.9V to 28V Input Common-Mode Voltage,
Independent of VDD
♦ Supply Voltage: +2.85V to +5.5V
♦ 700µA Supply Current, 1µA Shutdown Current
♦ Extended Temperature Range (-40°C to +85°C)
♦ Available in Space-Saving 10-Pin µMAX
Ordering Information
PART
MAX9922EUB+
PIN-
PACKAGE
10 µMAX
TEMP
RANGE
-40°C to +85°C
GAIN (V/V)
Adjustable
MAX9923TEUB+ 10 µMAX
MAX9923HEUB+ 10 µMAX
-40°C to +85°C
-40°C to +85°C
25
100
MAX9923FEUB+ 10 µMAX -40°C to +85°C
250
+Denotes a lead(Pb)-free/RoHS-compliant package.
Pin Configuration
TOP VIEW
RSB 1 +
RS+ 2
RS- 3
N.C. 4
GND 5
MAX9922
MAX9923T
MAX9923H
MAX9923F
10 VDD
9 OUT
8 FB
7 REF
6 SHDN
µMAX
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1 page  
Ultra-Precision, High-Side
Current-Sense Amplifiers
www.daEtasLhEeeCt4uT.cRomICAL CHARACTERISTICS (continued)
(VRSB = VRS+ = VRS- = +12V, VDD = +3.3V, VGND = 0, VREF = VDD/2 for bidirectional, VREF = 0 for unidirectional, VSENSE = VRS+ - VRS- = 0,
MAX9922 is set for AV =100V/V (R1 = 1kΩ, R2 = 99kΩ), SHDN = VDD, TA = -40°C to +85°C, unless otherwise noted. Typical values are at
TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
Power-Down Supply Current
IRSBL VDD = VREF = 0, VRSB = VRS+ = VRS- = 28V
0.05 1
µA
Power-Up Time
MAX9922, AV = 100V/V, VREF = 0, VSENSE =
10mV, VDD = 0 to 3.3V, settling to 0.1% of final
value
800
µs
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
All devices are 100% production tested at TA = +85°C. All temperature limits are guaranteed by design.
VOS is measured in bidirectional mode with VREF = VDD/2.
Data sheet limits are guaranteed by design and bench characterization. Thermocouple effects preclude measurement of
this parameter during production testing. Devices are screened during production testing to eliminate defective units.
VOS drift limits are guaranteed by design and bench characterization and are the average of drift from -40°C to +25°C and
from +25°C to +85°C.
VRSB = VRS+ = 12V, VREF = VDD/2 for bipolar mode and VREF = 0 for unipolar mode. Gain accuracy and gain linearity are
specified over a VSENSE range that keeps the output voltage 250mV away from the rails to achieve full accuracy. Output of
the part is rail-to-rail, and goes to within 25mV of the rails, but accuracy is not maintained. Linear operation is not guaran-
teed for VSENSE voltages > ±150mV. See the Typical Operating Characteristics section for plots of Input vs. Output.
This is the worst-case REF current needed to directly drive the bottom terminal of the gain setting resistors, at VDD = 3.3V,
and VREF = VDD/2. An internal 1kΩ resistor (R1) is present in the MAX9923T/MAX9923H/MAX9923F between the FB and
REF pins, while in the MAX9922 the resistor is external and user selectable. A voltage identical to the VSENSE develops
across this resistor. In all versions the REF input current is dependent on the magnitude and polarity of VSENSE, and in the
MAX9922 it is dependent on the value of the external resistor as well. See the External Reference section for more details.
The range of VREF, VCM, and VSENSE may limit the output swing of the MAX9922 with adjustable gain set to less than
100V/V.
_______________________________________________________________________________________ 5
5 Page 
Ultra-Precision, High-Side
Current-Sense Amplifiers
www.datasheet4u.com
-25mV
VOUT - VREF
5V
2.5V
AV = 100
CHARGE
CURRENT
0
DISCHARGE
CURRENT
-2.5V
25mV
( )VOUT = RSENSE x
1+
R2
R1
x ISENSE + VREF
Figure 1. Bidirectional Current-Sense Transfer Function
Shutdown
The MAX9922/MAX9923 feature a logic shutdown input
to reduce the supply current to less than 1µA. Drive
SHDN high for normal operation. Drive SHDN low to
place the device in shutdown mode. In shutdown
mode, the current drawn from both the VDD input and
the current-sense amplifier inputs (RSB, RS+, and RS-)
is less than 1µA each.
External Reference
The MAX9922/MAX9923 are capable of both unidirec-
tional and bidirectional operation. For unidirectional
current-sense applications, connect the REF input to
GND. For bidirectional, connect REF to a reference.
This sets bidirectional current sense with VOUT = VREF
for VSENSE = 0mV. Positive VSENSE causes OUT to
swing toward the positive supply, while negative
VSENSE causes OUT to swing toward GND. This feature
allows the output voltage to measure both charge and
discharge currents. Use VREF = VDD/2 for maximum
dynamic range.
In bidirectional operation, the external voltage applied
to VREF has to be able to supply the current in the feed-
back network between OUT, FB, and REF. This current
is simply the input sense voltage divided by the resis-
tance between FB and REF (1kΩ typical for MAX9923).
Furthermore, ensure the external voltage source sup-
plied to REF has a low source resistance to prevent
gain errors (e.g., use a stand-alone reference voltage
or an op amp to buffer a high-value resistor string.) See
the Typical Operating Circuits.
Input Differential Signal Range
The MAX9922/MAX9923 feature a proprietary input
structure optimized for small differential signals as low
as 10mV full scale for high efficiency with lowest power
dissipation in the sense resistor, or +100mV full scale for
high dynamic range. The output of the MAX9922/
MAX9923 allows for bipolar input differential signals.
Gain accuracy is specified over the VSENSE range to
keep the output voltage 250mV away from the rails to
achieve full accuracy. Output of the part is rail-to-rail
and goes to within 25mV of the rails, but accuracy is not
maintained. Linear operation is not guaranteed for input
sense voltages greater than ±150mV.
Applications Information
Power Supply, Bypassing, and Layout
Good layout technique optimizes performance by
decreasing the amount of stray capacitance at the
high-side, current-sense amplifier gain-setting pins, FB
to REF and FB to GND. Capacitive decoupling between
VDD to GND of 0.1µF is recommended. Since the
MAX9922/MAX9923 feature ultra-low input offset volt-
age, board leakage and thermocouple effects can easi-
ly introduce errors in the input offset voltage readings
when used with high-impedance signal sources.
Minimize board leakage current and thermocouple
effects by thoroughly cleaning the board and placing
the matching components very close to each other and
with appropriate orientation. For noisy digital environ-
ments, the use of a multilayer printed circuit board
(PCB) with separate ground and power-supply planes
is recommended. Keep digital signals far away from
the sensitive analog inputs. Unshielded long traces at
the input and feedback terminals of the amplifier can
degrade performance due to noise pick-up.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet MAX9922.PDF ] | |
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