MAX9923TEUB+T [MAXIM]
Operational Amplifier, 1 Func, 25uV Offset-Max, BICMOS, PDSO10, ROHS COMPLIANT, MO-187, USOP-10;
| 型号： | MAX9923TEUB+T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Operational Amplifier, 1 Func, 25uV Offset-Max, BICMOS, PDSO10, ROHS COMPLIANT, MO-187, USOP-10 放大器 |
| 文件： | 总15页 (文件大小：352K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4429; Rev 1; 1/10
Ultra-Precision, High-Side
Current-Sense Amplifiers
/MAX923
General Description
Features
The MAX9922/MAX9923 ultra-precision, high-side cur-
rent-sense amplifiers feature ultra-low offset voltage
OS
♦ Ultra-Precision V
Over Temperature
OS
MAX9922: ±±10V ꢀmaꢁx
MAX9923T: ±2ꢂ0V ꢀmaꢁx
MAX9923H: ±210V ꢀmaꢁx
MAX9923F: ±±10V ꢀmaꢁx
(V ) of 25µV (max) and laser-trimmed gain accuracy
better than 0.5%. The combination of low V and high-
OS
gain accuracy allows precise current measurements
even at very small sense voltages.
♦ ±1ꢃꢂ5 ꢀmaꢁx Full-Scale ꢄain Accuracꢅ
The MAX9922/MAX9923 are capable of both unidirec-
tional and bidirectional operation. For unidirectional
operation, connect REF to GND. For bidirectional oper-
♦ Bidirectional or Unidirectional I
SENSE
♦ Multiple ꢄains Available
Adjustable ꢀMAX9922x
+2ꢂV/V ꢀMAX9923Tx
ation, connect REF to V /2.
DD
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.
+±11V/V ꢀMAX9923Hx
+2ꢂ1V/V ꢀMAX9923Fx
♦ ±ꢃ9V to 28V Input Common-Mode Voltage,
Independent of V
DD
♦ Supplꢅ Voltage: +2ꢃ8ꢂV to +ꢂꢃꢂV
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-
♦ 7110A Supplꢅ Current, ±0A Shutdown Current
♦ Eꢁtended Temperature Range ꢀ-41°C to +8ꢂ°Cx
♦ Available in Space-Saving ±1-Pin 0MAX
mum full-scale V
voltage is critical.
SENSE
The MAX9922/MAX9923 use a spread-spectrum
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 tech-
nique, achieves less than 25µV (max) offset voltage.
Ordering Information
PIN-
TEMP
RANꢄE
PART
ꢄAIN ꢀV/Vx
PACKAꢄE
MAX9922EUB+
10 µMAX
-40°C to +85°C Adjustable
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.
MAX9923TEUB+ 10 µMAX
MAX9923HEUB+ 10 µMAX
MAX9923FEUB+ 10 µMAX
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
25
100
250
Applications
+Denotes a lead(Pb)-free/RoHS-compliant package.
Notebook/Desktop Power Management
Handheld Li+ Battery Current Monitoring
Precision Current Sources
Pin Configuration
TOP VIEW
+
RSB
RS+
RS-
1
2
3
4
5
10
9
V
DD
OUT
FB
MAX9922
MAX9923T
MAX9923H
MAX9923F
Tꢅpical Operating Circuits appear at end of data sheetꢃ
8
N.C.
GND
7
REF
SHDN
µMAX is a registered trademark of Maxim Integrated Products, Inc.
6
µMAX
________________________________________________________________ Maꢁim Integrated Products
±
For pricing, deliverꢅ, and ordering information, please contact Maꢁim Direct at ±-888-629-4642,
or visit Maꢁim’s website at wwwꢃmaꢁim-icꢃcomꢃ
Ultra-Precision, High-Side
Current-Sense Amplifiers
ABSOLUTE MAXIMUM RATINGS
RSB, RS+, RS- to GND...........................................-0.3V to +30V
Current into Any Pin.......................................................... 20mA
V
to GND..............................................................-0.3V to +6V
Continuous Power Dissipation (T = +70°C)
DD
A
OUT, REF, FB, SHDN
to GND .................-0.3V to the lower of (V + 0.3V) and +6V
OUT Short Circuit to V
10-Pin µMAX (derate 4.5mW/°C above +70°C)...........362mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
DD
or GND ..............................Continuous
DD
Differential Voltage (V
- V ), (V
- V
),
RS+
RS+
RS-
RSB
(V
- V )................................................................... 5.5V
RSB
RS-
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
=
= V
= V
RS- =
+12V, V = +3.3V, V
= 0V, V
= V /2 for bidirectional, V
= 0V for unidirectional, V
= V - V
RS+ RS-
RSB
RS+
DD
GND
REF
DD
REF
SENSE
0V, MAX9922 is set for A =100V/V (R1 = 1kΩ, R2 = 99kΩ), SHDN = V , T = -40°C to +85°C, unless otherwise noted. Typical values
are at T = +25°C.) (Note 1)
A
V
DD
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
/MAX923
DC CHARACTERISTICS
MAX9922 (A = 100), V
= 0V,
V
SENSE
0.1
0.2
0.2
0.1
10
25
20
10
V
= V /2, -40°C ≤ T ≤ +85°C
REF
DD
A
MAX9923T, V
= 0V, V
= V /2,
REF DD
SENSE
-40°C ≤ T ≤ +85°C
A
Input Offset Voltage
(Notes 2, 3)
V
µV
OS
MAX9923H, V
= 0V, V
= V /2
DD
SENSE
REF
-40°C ≤ T ≤ +85°C
A
MAX9923F, V
= 0V, V
= V /2,
DD
SENSE
REF
-40°C ≤ T ≤ +85°C
A
MAX9922 (A = 100V/V), V
= 0V,
V
SENSE
0.05
V
= V /2, -40°C ≤ T ≤ +85°C
REF
DD
A
MAX9923T, V
= 0V, V
= V /2,
REF DD
SENSE
0.20
0.10
-40°C ≤ T ≤ +85°C
Input Offset Voltage
Temperature Drift (Notes 2, 4)
A
TCV
µV/°C
OS
MAX9923H, V
= 0V, V
= V /2,
DD
SENSE
REF
-40°C ≤ T ≤ +85°C
A
MAX9923F, V
= 0V, V
= V /2,
DD
SENSE
REF
0.05
-40°C ≤ T ≤ +85°C
A
Input Common-Mode Range
Input Common-Mode Rejection
V
Guaranteed by CMRR
1.90
121
28.00
V
CMR
1.9V ≤ V
≤ 28V, -40°C ≤ T ≤ +85°C
A
RS+
CMRR
140
dB
(Note 2)
MAX9922
Adj
25
MAX9923T
MAX9923H
MAX9923F
A
V
Gain
V/V
100
250
2
_______________________________________________________________________________________
Ultra-Precision, High-Side
Current-Sense Amplifiers
/MAX923
ELECTRICAL CHARACTERISTICS (continued)
(V
=
= V
= V
RS- =
+12V, V = +3.3V, V
= 0V, V
= V /2 for bidirectional, V
= 0V for unidirectional, V
= V - V
RS+ RS-
RSB
RS+
DD
GND
REF
DD
REF
SENSE
0V, MAX9922 is set for A =100V/V (R1 = 1kΩ, R2 = 99kΩ), SHDN = V , T = -40°C to +85°C, unless otherwise noted. Typical values
are at T = +25°C.) (Note 1)
A
V
DD
A
PARAMETER
SYMBOL
CONDITIONS
= +25°C
MIN
TYP
MAX
0.40
0.60
0.30
0.60
0.40
0.75
0.50
0.80
UNITS
T
A
0.17
MAX9922
(A = 100)
V
-40°C ≤ T ≤ +85°C
A
T
A
= +25°C
0.12
0.24
0.21
MAX9923T
MAX9923H
MAX9923F
-40°C ≤ T ≤ +85°C
Gain Accuracy
(Note 5)
A
∆A
%
V
T
A
= +25°C
-40°C ≤ T ≤ +85°C
A
T
A
= +25°C
-40°C ≤ T ≤ +85°C
A
MAX9922 (A = 100)
V
0.06
0.04
0.06
0.12
160
1
MAX9923T
MAX9923H
MAX9923F
MAX9922
Gain Nonlinearity
~A
%
V
Open-Loop Gain
Input Bias Current
FB Bias Current
A
dB
pA
pA
VOL
I
I
RS+, RS-
I
MAX9922
1
FB
MAX9923T/MAX9923H/MAX9923F resistance
between FB and REF
FB Resistance
R
1
kΩ
FB
V
1.4
-
-
DD
T
= +25°C
0
0
A
Guaranteed by REF
CMRR test
REF Input Range
V
V
1.6
DD
-40°C ≤ T ≤ +85°C
A
REF Common-Mode Rejection
Ratio
0 ≤ REF ≤ V
- 1.4V (Note 2)
94
100
dB
µA
DD
MAX9922 (bidirectional)
MAX9923T (bidirectional)
MAX9923H (bidirectional)
MAX9923F (bidirectional)
20
70
20
7
60
16
6
REF Input Current
(Note 6)
R = 10kΩ to GND
and REF = GND
L
7
1
30
6
V
= V
– V
DD OUT
OH
OUT High Voltage
V
mV
OH
(Note 7)
R = 10kΩ to V
L
DD
and REF = V - 1.4
DD
R = 10kΩ to GND and REF = GND
1
6
10
30
L
OUT Low Voltage (Note 7)
SHDN Logic-Low
V
V
mV
V
OL
R = 10kΩ to V
L
and REF = V - 1.4
DD
DD
V
V
= 5.5V
0.3
IL
DD
0.6 x
SHDN Logic-High
V
= 5.5V
V
IH
DD
V
DD
SHDN Input Current
I
/I
IH IL
0.001
1
µA
_______________________________________________________________________________________
3
Ultra-Precision, High-Side
Current-Sense Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(V
=
= V
= V
RS- =
+12V, V = +3.3V, V
= 0V, V
= V /2 for bidirectional, V
= 0V for unidirectional, V
= V - V
RS+ RS-
RSB
RS+
DD
GND
REF
DD
REF
SENSE
0V, MAX9922 is set for A =100V/V (R1 = 1kΩ, R2 = 99kΩ), SHDN = V , T = -40°C to +85°C, unless otherwise noted. Typical values
are at T = +25°C.) (Note 1)
A
V
DD
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
AC CHARACTERISTICS
MAX9922
10
V
V
= 10mV
MAX9923T
MAX9923H
MAX9923F
SENSE
SENSE
P-P
50
10
-3dB Small-Signal Bandwidth
Slew Rate
BW
SR
kHz
V/µs
µs
= 5mV
P-P
2.5
0.4
200
∆V
= 2V, C = 100pF
LOAD
OUT
MAX9922
MAX9923T
MAX9923H
100
200
400
OUT Settling Time to 1% of
Final Value
C
= 7pF
LOAD
MAX9923F
/MAX923
Input-Voltage Noise
Peak-to-Peak
f
=0.1Hz to 10Hz
3.4
µV
P-P
O
Autozeroing Clock Frequency
Capacitive-Load Stability
f
Pseudo-random
20
kHz
C
No sustained oscillations
200
pF
POWER-SUPPLY CHARACTERISTICS
Supply Voltage Range
V
Guaranteed by PSRR
2.85
93
5.50
V
DD
2.85V ≤ V
≤ 5.5V, -40°C ≤ T ≤ +85°C
A
DD
Power-Supply Rejection Ratio
PSRR
99
dB
(Note 2)
V
V
V
V
V
= 5.0V
780
700
200
0.05
0.05
1300
1500
300
1
DD
I
DD
Quiescent Supply Current
µA
= 3.0V
DD
I
= 12V
RSB
RSB
I
= 0.3V
DD_SD
SHDN
SHDN
Shutdown Supply Current
Power-Down Input Current
µA
µA
I
= 0.3V, V
= 28V
RSB
1
RSB_SD
I
RS+L,
RS-L
V
= V
= 0V, V
= V
= V = 28V
RS-
0.01
0.1
DD
REF
RSB
RS+
I
4
_______________________________________________________________________________________
Ultra-Precision, High-Side
Current-Sense Amplifiers
/MAX923
ELECTRICAL CHARACTERISTICS (continued)
(V
=
= V
= V
RS- =
+12V, V = +3.3V, V
= 0V, V
= V /2 for bidirectional, V
= 0V for unidirectional, V
= V - V
RS+ RS-
RSB
RS+
DD
GND
REF
DD
REF
SENSE
0V, MAX9922 is set for A =100V/V (R1 = 1kΩ, R2 = 99kΩ), SHDN = V , T = -40°C to +85°C, unless otherwise noted. Typical values
are at T = +25°C.) (Note 1)
A
V
DD
A
PARAMETER
SYMBOL
CONDITIONS
= 0V, V = V
MIN
TYP
MAX
UNITS
Power-Down Supply Current
I
V
= V
= V = 28V
RS-
0.05
1
µA
RSBL
DD
REF
RSB
RS+
MAX9922, A = 100V/V, V
= 0V, V
=
SENSE
V
REF
Power-Up Time
800
µs
10mV, V
value
= 0V to 3.3V, settling to 0.1% of final
DD
Note 1: All devices are 100% production tested at T = +85°C. All temperature limits are guaranteed by design.
A
Note 2:
V
OS
is measured in bidirectional mode with V = V /2.
REF DD
Note 3: 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.
Note 4:
Note 5:
V
drift limits are guaranteed by design and bench characterization and are the average of drift from -40°C to +25°C and
OS
from +25°C to +85°C.
= V = 12V, V
V
RSB
= V /2 for bipolar mode and V
= 0V for unipolar mode. Gain accuracy and gain linearity are
RS+
REF
DD
REF
specified over a V
range that keeps the output voltage 250mV away from the rails to achieve full accuracy. Output of
SENSE
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 V voltages > 150mV. See the Typical Operating Characteristics section for plots of Input vs. Output.
SENSE
Note 6: This is the worst-case REF current needed to directly drive the bottom terminal of the gain setting resistors, at V
= 3.3V,
DD
and V
= V /2 while maintaining gain accuracy. An internal 1kΩ resistor (R1) is present in the MAX9923T/
REF
DD
MAX9923H/MAX9923F between the FB and REF pins, while in the MAX9922 the resistor is external and user selectable. A
voltage identical to the V develops across this resistor. In all versions the REF input current is dependent on the mag-
SENSE
nitude and polarity of V
, and in the MAX9922 it is dependent on the value of the external resistor as well. The input
SENSE
bias current for REF is typically 1pA in the MAX9922 since it connects to the gate of a MOS transistor. See the External
Reference section for more details.
Note 7: The range of V
, V , and V
may limit the output swing of the MAX9922 with adjustable gain set to less than
REF
CM
SENSE
100V/V.
_______________________________________________________________________________________
5
Ultra-Precision, High-Side
Current-Sense Amplifiers
Typical Operating Characteristics
(V
= 3.3V, V
= V , V
= V
= V
= 12V, T = +25°C, unless otherwise noted.)
RS- A
DD
SHDN
DD RSB
RS+
MAX9922 UNIPOLAR
GAIN ACCURACY HISTOGRAM
MAX9922 INPUT
OFFSET VOLTAGE HISTOGRAM
MAX9922
OFFSET VOLTAGE DRIFT HISTOGRAM
90
80
70
60
60
50
40
30
20
10
0
50
40
30
20
10
0
60
50
40
30
20
10
0
-0.5 -0.4 -0.3 -0.2 -0.1
0
0.1 0.2 0.3 0.4 0.5
-10 -8 -6 -4 -2
0
2
4
6
8
10
-50 -40 -30 -20 -10
0
10 20 30 40 50
/MAX923
GAIN ACCURACY (%)
V
OS
(µV)
TCV (nV/°C)
OS
INPUT REFERRED OFFSET
vs. INPUT COMMON-MODE VOLTAGE
MAX9922
INPUT vs. OUTPUT
MAX9922
INPUT vs. OUTPUT
8
6
2.0
1.5
1.0
0.5
0
2.0
1.5
1.0
0.5
0
R = 100kΩ
G
R = 100kΩ
G
F
F
R
= 1kΩ
R
= 20kΩ
4
2
0
-2
-4
-6
-8
-0.5
-1.0
-1.5
-2.0
-0.5
-1.0
-1.5
-2.0
0
4
8
12
16
20
24
28
-250
-150
-50
0
50
150
250
-25
-15
-5
0
5
15
25
INPUT COMMON MODE (V)
DIFFERENTIAL INPUT (mV)
DIFFERENTIAL INPUT (mV)
GAIN ERROR
vs. INPUT COMMON-MODE VOLTAGE
V /V
OH OL
vs. I /I
OH OL
0.5
0.4
0.3
0.2
0.1
0
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
REF = GND
V
OH
6
V
OL
0
0
0
5
10
15
20
25
2
4
8
10
INPUT COMMON MODE (V)
OUTPUT CURRENT (mA)
6
_______________________________________________________________________________________
Ultra-Precision, High-Side
Current-Sense Amplifiers
/MAX923
Typical Operating Characteristics (continued)
(V
= 3.3V, V
= V , V
= V
= V
= 12V, T = +25°C, unless otherwise noted.)
RS- A
DD
SHDN
DD RSB
RS+
SUPPLY CURRENT
vs. TEMPERATURE
RSB CURRENT
vs. TEMPERATURE
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.4
0.3
0.2
0.1
0
V
= 28V
RSB
V
= 12V
V
= 5.5V
RSB
DD
V
= 3.3V
DD
V
= 2.85V
DD
V
= 1.9V
RSB
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX9922
GAIN vs. FREQUENCY
140
120
100
80
30
25
20
15
10
5
GAIN = OPEN LOOP
V
= 2.85V
DD
V
DD
= 5.5V
60
40
GAIN = 1000
V
= 3.3V
DD
20
0
0
-40
-15
10
35
60
85
10E-3
1E+0
100E+0
10E+0
10E+3
100E+3
1E+6
100E-3
1E+3
TEMPERATURE (°C)
FREQUENCY (Hz)
PSRR
vs. FREQUENCY
INPUT CMRR
vs. FREQUENCY
-60
-60
-70
-70
-80
-80
-90
-90
-100
-100
-110
-120
-130
-110
-120
-130
-140
-140
1E+0
10E+0 100E+0 1E+3
FREQUENCY (Hz)
10E+3 100E+3
1E+0
10E+0 100E+0 1E+3
FREQUENCY (Hz)
10E+3 100E+3
_______________________________________________________________________________________
7
Ultra-Precision, High-Side
Current-Sense Amplifiers
Typical Operating Characteristics (continued)
(V
= 3.3V, V
= V , V
= V
= V
= 12V, T = +25°C, unless otherwise noted.)
RS- A
DD
SHDN
DD RSB
RS+
PEAK-TO-PEAK NOISE
INPUT NOISE DENSITY
vs. FREQUENCY
(0.1Hz TO 10Hz)
MAX9922/23 toc16
250
200
150
100
50
1.25µV/div
32kHz SPIKE ENERGY
= 4.3µVRMS
0
1s/div
10
100
1,000
10,000 100,000
FREQUENCY (Hz)
/MAX923
POWER-ON RESPONSE
LARGE SIGNAL INPUT
(MAX9922, A = 100)
STEP RESPONSE (MAX9922, A = 100)
V
V
INPUT
(10mV/div)
0V
0V
OUT
(500mV/div)
0V
0V
OUTPUT
(1V/div)
V
DD
(1V/div)
V
= 10mV
SENSE
TIME (200µs/div)
TIME (80µs/div)
SHUTDOWN ON/OFF TRANSIENT
(MAX9922, A = 100)
V
SHDN
(1V/div)
0V
0V
OUTPUT
(500mV/div)
V
= 10mV
SENSE
TIME (200µs/div)
8
_______________________________________________________________________________________
Ultra-Precision, High-Side
Current-Sense Amplifiers
/MAX923
Typical Operating Characteristics (continued)
(V
= 3.3V, V
= V , V
= V
= V
= 12V, T = +25°C, unless otherwise noted.)
RS- A
DD
SHDN
DD RSB
RS+
OVERLOAD RECOVERY
(OUTPUT LIMITING) (MAX9922, A = 100)
SATURATION/OVERLOAD RECOVERY
(INPUT LIMITED) (MAX9922)
V
INPUT
(50mV/div)
INPUT
(100mV/div)
0V
0V
0V
OUTPUT
(1V/div)
OUTPUT
(1V/div)
0V
GAIN = 5V/V
TIME (150µs/div)
TIME (200µs/div)
Pin Description
PIN
1
NAME
RSB
RS+
RS-
FUNCTION
Current-Sense Amplifier Input Stage Supply. Connect to either RS+ or RS-.
Current-Sense Amplifier Positive Input
Current-Sense Amplifier Negative Input
No Connection. Not internally connected.
Ground
2
3
4
N.C.
GND
5
6
SHDN Shutdown Logic Input. Connect to GND to reduce quiescent current to 1µA. Connect to V
for normal operation.
DD
Reference Voltage Input. Connect to an external voltage to provide a bidirectional current-sense output. Connect
to GND for unidirectional operation.
7
8
REF
Gain-Set Feedback Input. Connect an optional noise reduction capacitor between OUT and FB.
MAX9922: Adjustable Gain. Connect a resistive-divider feedback network between OUT, FB, and REF to set the
current-sense amplifier gain. Use an external combination of R1 and R2 resistors for gain = 1 + (R2/R1).
FB
MAX9923T/MAX9923H/MAX9923F: Fixed gain. See the Functional Diagrams.
9
OUT
Voltage Output. V
is proportional to V
.
OUT
SENSE
10
V
Power-Supply Voltage Input. Bypass to GND with a 0.1µF capacitor.
DD
_______________________________________________________________________________________
9
Ultra-Precision, High-Side
Current-Sense Amplifiers
Functional Diagrams
1
2
10
9
1
2
10
RSB
RS+
RS-
V
DD
RSB
RS+
RS-
V
DD
9
OUT
R2
OUT
R2
3
4
8
7
3
4
8
FB
FB
R1
R1
7
REF
N.C.
REF
N.C.
MAX9922
GAIN = 1 +
MAX9923
6
5
6
5
GND
SHDN
GND
SHDN
/MAX923
R2
(R1 )
MAX9923
VERSION
GAIN
25
T
H
F
100
250
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.)
Detailed Description
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 ). This
DD
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.
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
yield a positive and negative
REF
The MAX9922/MAX9923 monitor current through a cur-
rent-sense resistor and amplify the voltage across the
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.)
resistor. The 28V input common-mode voltage (V
)
RS+
range of the MAX9922/MAX9923 is independent of the
supply voltage (V ). High-side current monitoring
DD
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.
10 ______________________________________________________________________________________
Ultra-Precision, High-Side
Current-Sense Amplifiers
/MAX923
In bidirectional operation, the external voltage applied
to V
has to be able to supply the current in the feed-
REF
5V
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.
V
- V
REF
OUT
A
= 100
V
2.5V
CHARGE
CURRENT
-25mV
0
25mV
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.
DISCHARGE
CURRENT
-2.5V
Gain accuracy is specified over the V
range to
SENSE
R2
V
= R
x
1 +
x I
+ V
REF
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.
OUT
SENSE
(
)
SENSE
R1
Figure 1. Bidirectional Current-Sense Transfer Function
Applications Information
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
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
mode, the current drawn from both the V
input and
DD
the current-sense amplifier inputs (RSB, RS+, and RS-)
is less than 1µA each.
V
to GND of 0.1µF is recommended. Since the
DD
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.
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 V
= V
REF
OUT
for V
= 0mV. Positive V
causes OUT to
SENSE
SENSE
swing toward the positive supply, while negative
causes OUT to swing toward GND. This feature
V
SENSE
allows the output voltage to measure both charge and
discharge currents. Use V
dynamic range.
= V /2 for maximum
DD
REF
______________________________________________________________________________________ 11
Ultra-Precision, High-Side
Current-Sense Amplifiers
Optional Noise Reduction Capacitor
A noise reduction capacitance of ~1nF can be con-
nected between OUT and FB, if needed. Noise reduc-
tion is achieved by both limiting the amplifier
bandwidth, reducing contribution of broadband white
noise and by attenuating contribution of any small
20kHz autozero ripple that appears at the output. Using
higher values of feedback capacitance reduces the
output noise of the amplifier, but also reduces its signal
bandwidth.
Sense Resistor Connections
Take care to prevent solder and trace resistance from
causing errors in the sensed voltage because of the high
currents that flow through R
. Either use a four termi-
SENSE
nal current-sense resistor or use Kelvin (force and sense)
PCB layout techniques to minimize these errors.
Efficiency and Power Dissipation
At high current levels, the I2R losses in R
can be
SENSE
significant. Take this into consideration when choosing
the resistor value and its power dissipation (wattage)
rating. The sense resistor’s value will drift if it is allowed
to heat up excessively. The precision V
of the
OS
MAX9922/MAX9923 allows the use of small sense resis-
tors to reduce power dissipation and reduce hot spots.
/MAX923
12 ______________________________________________________________________________________
Ultra-Precision, High-Side
Current-Sense Amplifiers
/MAX923
Typical Operating Circuits
Unidirectional Mode
V
SENSE
R
LOAD
RS+
RS-
BATT
1.9V TO
28V
RSB
3.3V
V
DD
12-BIT ADC
OUT
MAX9923T
MAX9923H
MAX9923F
1nF*
FB
ON
SHDN
REF
GND
OFF
*OPTIONAL NOISE REDUCTION
Bidirectional Mode
V
SENSE
TO WALL-CUBE/CHARGER
R
LOAD
RS+
RS-
BATT
1.9V TO
28V
RSB
3.3V
V
DD
12-BIT ADC
= 2.5V
OUT
V
REF
MAX9923T
MAX9923H
MAX9923F
1nF*
FB
1.25V
ON
SHDN
REF
GND
OFF
*OPTIONAL NOISE REDUCTION
Chip Information
PROCESS: BiCMOS
______________________________________________________________________________________ 13
Ultra-Precision, High-Side
Current-Sense Amplifiers
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the
package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the
package regardless of RoHS status.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
21-0061
10 µMAX
U10-2
/MAX923
α
α
14 ______________________________________________________________________________________
Ultra-Precision, High-Side
Current-Sense Amplifiers
/MAX923
Revision History
REVISION REVISION
PAGES
DESCRIPTION
CHANGED
NUMBER
DATE
0
1
3/09
1/10
Initial release
Updated conditions for REF input current and Note 6
—
3, 5
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 15
© 2010 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
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