MAX9934TART+ [MAXIM]
Analog Circuit, 1 Func, BICMOS, PBGA6, 1 X 1.50 MM, 0.60 MM HEIGHT, ROHS COMPLIANT, UCSP-6;
| 型号： | MAX9934TART+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Analog Circuit, 1 Func, BICMOS, PBGA6, 1 X 1.50 MM, 0.60 MM HEIGHT, ROHS COMPLIANT, UCSP-6 信息通信管理 |
| 文件： | 总19页 (文件大小：855K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
EVALUATION KIT AVAILABLE
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
General Description
Features
The MAX9934 high-precision, low-voltage, high-side
current-sense amplifier is ideal for both bidirectional
(charge/discharge) and unidirectional current measure-
ments in battery-powered portable and laptop devices.
o Input Offset Voltage: 10µV (max)
o Gain Error Less than 0.25%
o -0.1V to +5.5V Input Common-Mode Voltage
Range
Input offset voltage (V ) is a low 10µV (max) at +25°C
OS
across the -0.1V to 5.5V input common-mode voltage
o Chip Select Allows Multiplexing Several MAX9934
range, and is independent of V . Its precision input
CC
Current Monitors to One ADC
specification allows the use of very small sense volt-
ages (typically 10mV full-scale) for minimally invasive
current sensing.
o Current Output Allows R
Selection
OUT
for Gain Flexibility
o Single Supply Operation: 2.5V to 3.6V
The output of the MAX9934 is a current proportional to
input V
and is available in either 25µA/mV or
o Two Gain Options: G of 25µA/mV (MAX9934T)
SENSE
M
5µA/mV gain options (G ) with gain accuracy better
and 5µA/mV (MAX9934F)
M
than 0.25% (max) at +25°C. A chip select (CS) allows
multiplexing of several MAX9934 current outputs to a
single microcontroller ADC channel (see the Typical
Operating Circuit). CS is compatible with 1.8V and 3.3V
logic systems.
o Bidirectional or Unidirectional Operation
o Small, 6-Bump UCSP (1mm x 1.5mm x 0.6mm)
and 8-Pin µMAX Packages
The MAX9934 is designed to operate from a 2.5V to
Ordering Information
3.6V V
supply, and draws just 120µA (typ) quiescent
CC
current. When powered down (V
= 0), RS+ and RS-
PIN-
PACKAGE
TOP
MARK
CC
PART
GAIN
draw less than 0.1nA (typ) leakage current to reduce
battery load. The MAX9934 is robust and protected
from input faults of up to 6V input differential voltage
between RS+ and RS-.
MAX9934FART+T
MAX9934FAUA+T
MAX9934FAUA/V+T
MAX9934TART+T
MAX9934TAUA+T
MAX9934TAUA/V+T
5µA/mV
5µA/mV
5µA/mV
25µA/mV
25µA/mV
25µA/mV
6 UCSP
8 µMAX
8 µMAX
6 UCSP
8 µMAX
8 µMAX
AAG
—
AAG
AAF
—
The MAX9934 is specified for operation over the -40°C
to +125°C temperature range and is available in an
8-pin µMAX® or a 6-bump UCSP™ (1mm x 1.5mm x
0.6mm), making it ideal for space-sensitive applications.
AAF
Note: All devices are specified over the -40°C to +125°C
extended temperature range.
Applications
PDAs and Smartphones
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
MP3 Players
Sensor Instrumentation Amplifiers
Notebook PCs and Ultra-Mobile PCs
Portable Current Monitoring
Typical Operating Circuit
V
CC
= 3.3V
0.1µF
I
LOAD
-0.1V ≤ V ≤ 5.5V
CM
V
CC
R
SENSE
MAX9934
RS-
RS+
V
TO ADC
OUT
OUT
R
OUT
10kΩ
1000pF
GND
CS
µMAX is a registered trademark and UCSP is a trademark of
Maxim Integrated Products, Inc.
FROM µC
CHIP SELECT
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
19-5011; Rev 3; 11/12
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
ABSOLUTE MAXIMUM RATINGS
RS+, RS- to GND......................................................-0.3V to +6V
Junction-to-Case Thermal Resistance (θ
)
JC
V
to GND..............................................................-0.3V to +4V
(Note 1) ......................................................................42°C/W
CC
CS, OUT to GND (V
= 0, or CS < V )..................-0.3V to +4V
6-Bump UCSP (derate multilayer 3.9mW/°C
above +70°C).............................................................308mW
Junction-to-Ambient Thermal Resistance (θ
(Note 1) ....................................................................260°C/W
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (µMAX only, soldering, 10s)..............+300°C
Soldering Temperature (reflow) .......................................+260°C
CC
IL
OUT to GND (CS > V )................................-0.3V to V
+ 0.3V
CC
IH
Differential Input Voltage (RS+ - RS-).................................... 6V
Output Short-Circuit Current Duration
OUT to GND or V ...............................................Continuous
CC
Continuous Input Current into Any Terminal..................... 20mA
)
JA
Continuous Power Dissipation (T = +70°C)
A
8-Pin µMAX (derate multilayer 4.8mW/°C
above +70°C).............................................................388mW
Junction-to-Ambient Thermal Resistance (θ
)
JA
(Note 1) ....................................................................206°C/W
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
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
= 3.3V, V
= V
= 3.0V, V
= 0V, V
= (V
+ V )/2, V = 3.3V, R
= 10kΩ to GND for unidirectional opera-
CM
RS+
RS-
CC
tion, R
RS+
RS-
CC
SENSE
CS
OUT
= 10kΩ to V /2 for bidirectional operation. T = -40°C to +125°C, unless otherwise noted. Typical values are at T
=
OUT
A
A
+25°C.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DC CHARACTERISTICS
T
= +25°C
10
14
10
20
60
90
A
MAX9934T
MAX9934F
-40°C ≤ T ≤ +125°C
A
Input Offset Voltage (Note 3)
V
µV
OS
T
A
= +25°C
-40°C ≤ T ≤ +125°C
A
MAX9934T
MAX9934F
Input Offset Voltage Drift (Note 3)
Common-Mode Input Voltage
V
/dT
nV/°C
V
OS
Range (Average of V
and
CMVR
Guaranteed by CMRR2
-0.1
+5.5
RS+
V
) (Note 3)
RS-
T
= +25°C
128
112
128
109
119
104
98
134
135
125
113
A
0 ≤ V
0.2V (MAX9934F)
≤ V
-
CC
CM
-40°C ≤ T ≤ +125°C
A
CMRR1
T
A
= +25°C
0 ≤ V ≤ V
0.2V (MAX9934T)
-
CC
CM
-40°C ≤ T ≤ +125°C
A
Common-Mode Rejection Ratio
(Note 3)
dB
T
A
= +25°C
-0.1 ≤ V ≤ 5.5V
(MAX9934F)
CM
-40°C ≤ T ≤ +125°C
A
CMRR2
T
A
= +25°C
-0.1 ≤ V ≤ 5.5V
CM
(MAX9934T)
-40°C ≤ T ≤ +125°C
98
A
2
Maxim Integrated
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
ELECTRICAL CHARACTERISTICS (continued)
(V
= 3.3V, V
= V
= 3.0V, V
= 0V, V
= (V
+ V )/2, V = 3.3V, R
= 10kΩ to GND for unidirectional opera-
CM
RS+
A
RS-
CC
tion, R
RS+
RS-
CC
SENSE
CS
OUT
= 10kΩ to V /2 for bidirectional operation. T = -40°C to +125°C, unless otherwise noted. Typical values are at T
=
OUT
A
+25°C.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
25
5
MAX
UNITS
MAX9934T
MAX9934F
Current Gain (Transconductance)
G
µA/mV
M
T
= +25°C
0.25
2.0
A
MAX9934T
MAX9934F
-40°C ≤ T ≤ +125°C
Current Gain Error
(Note 4)
A
G
%
ME
T
A
= +25°C
0.25
2.4
-40°C ≤ T ≤ +125°C
A
MAX9934T
MAX9934F
200
240
100
100
60
Gain Error Drift
G
/dT
ppm/°C
ME
Input-Bias Current for RS+
Input-Bias Current for RS-
I
V
V
V
V
= V
= V
= V
= 5.5V
0.1
0.1
35
nA
nA
µA
nA
BRS+
RS+
RS+
RS+
RS-
RS-
RS-
≤ V
- 0.2V
CC
I
BRS-
= 5.5V
= V = 5.5V
RS-
Input Leakage Current
I
= 0V, V
0.1
100
LEK
CC
RS+
DC CHARACTERISTICS
Minimum Current for Output Low
I
Unidirectional, V = I x R
OUT
1
100
0.25
0.25
0.30
0.26
nA
V
OL
OL
OL
V
I
I
I
I
= +600µA, V
= V - V
0.1
OH
OUT
OUT
OUT
OUT
OH
CC
OUT
Output-Voltage Range
(MAX9934T)
V
= -600µA, bidirectional
= +375µA, V = V - V
0.15
0.18
0.18
OL
V
OH
OH
CC
OUT
Output-Voltage Range
(MAX9934F)
V
V
= -375µA, bidirectional
OL
Deselected Amplifier Output
Leakage
V
CS
and 0 ≤ V
= 0V, V = 3.6V,
OUT
I
0.1
0.1
100
nA
OLK
≤ 3.6V
CC
LOGIC I/O (CS)
Input Voltage Low CS
Input Voltage High CS
Input Current CS
V
0.54
V
V
IL
V
1.26
100
IH
I ,I
IL IH
0 ≤ V ≤ V
CC
nA
CS
POWER SUPPLY
Supply-Voltage Range
V
Guaranteed by PSRR
2.5V ≤ V ≤ 3.6V,
2.5
3.6
V
CC
CC
Power-Supply Rejection Ratio
Supply Current
PSRR
110
120
120
120
dB
V
= V
= 2V (Note 3)
RS+
RS-
V
V
= 3.3V, R
= 10kΩ to 3.3V,
OUT
CC
I
230
210
µA
µA
CC
= V
= 3.1V
RS+
RS-
Supply Current, Output
Deselected
V
V
= 0V, R
= 10kΩ to 3.3V,
CS
OUT
I
CC,DES
= V
= 3.1V
RS-
RS+
AC CHARACTERISTICS (C = 1000pF)
L
MAX9934T
= 25µA/mV, V
1.5
5
G
= 5mV
SENSE
M
Amplifier Bandwidth
Maxim Integrated
BW
kHz
MAX9934F
= 5µA/mV, V
G
= 25mV
SENSE
M
3
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
ELECTRICAL CHARACTERISTICS (continued)
(V
= 3.3V, V
= V
= 3.0V, V
= 0V, V
= (V
+ V )/2, V = 3.3V, R
= 10kΩ to GND for unidirectional opera-
CM
RS+
A
RS-
CC
tion, R
RS+
RS-
CC
SENSE
CS
OUT
= 10kΩ to V /2 for bidirectional operation. T = -40°C to +125°C, unless otherwise noted. Typical values are at T
=
OUT
A
+25°C.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
670
220
MAX
UNITS
0.1% final value, Figure 1, MAX9934T
0.1% final value, Figure 1, MAX9934F
Output Settling Time
Output Select Time
t
µs
S
Output to 0.1% final value, Figure 2,
MAX9934T
150
80
2
t
µs
ZH
Output to 0.1% final value, Figure 2,
MAX9934F
Output step of 100mV, C = 10pF,
L
Output Deselect Time
Power-Down Time
Power-Up Time
t
t
t
µs
µs
µs
HZ
PD
PU
Figure 2
Output step of -100mV, C = 10pF,
L
2
V
> 2.5V
CC
0.1% final value, Figure 3, MAX9934T
0.1% final value, Figure 3, MAX9934F
300
200
Note 2: All devices are 100% production tested at T = +25°C. Unless otherwise noted, specifications overtemperature are guaran-
A
teed by design.
Note 3: Guaranteed by design. Thermocouple, contact resistance, RS- input-bias current, and leakage effects preclude measure-
ment of this parameter during production testing. Devices are screened during production testing to eliminate defective
units.
Note 4: Gain error tested in unidirectional mode: 0.2V ≤ V
≤ 3.1V for the MAX9934T; 0.25V ≤ V
≤ 2.5V for the MAX9934F.
OUT
OUT
4
Maxim Integrated
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
Typical Operating Characteristics
(V
= 3.3V, V
= V
= 3.0V, V
= 0V, C = 1000pF, R
= 10kΩ to GND for unidirectional operation, R
= 10kΩ to
CC
RS+
RS-
SENSE
L
OUT
OUT
V
CC
/2 for bidirectional operation. T = +25°C, unless otherwise noted.)
A
OFFSET VOLTAGE
vs. COMMON-MODE VOLTAGE
MAX9934T V HISTOGRAM
MAX9934T DRIFT V HISTOGRAM
OS
OS
10
8
40
30
25
20
15
10
5
35
30
25
20
15
10
5
T
A
= +125NC
6
4
2
0
T
A
= +25NC
-2
-4
-6
-8
-10
T
A
= -40NC
0
0
-0.1 0.6 1.3 2.0 2.7 3.4 4.1 4.8 5.5
COMMON-MODE VOLTAGE (V)
-10 -8 -6 -4 -2
0
2
4
6
8
10
0
6
12 18 24 30 36 42 48 54 60
VOS (FV)
TCVOS (nV/NC)
OFFSET VOLTAGE
vs. COMMON-MODE VOLTAGE
MAX9934T GAIN ERROR
HISTOGRAM
MAX9934T GAIN ERROR
DRIFT HISTOGRAM
10
8
30
25
20
15
10
5
35
30
25
20
15
10
5
6
V
CC
= 2.5V
V
CC
= 3.3V
4
2
0
V
= 3.6V
CC
-2
-4
-6
-8
-10
0
0
-0.1 0.6 1.3 2.0 2.7 3.4 4.1 4.8 5.5
COMMON-MODE VOLTAGE (V)
GE (%)
TC GE (PPM/NC)
V
vs. V
SENSE
MAX9934F GAIN ERROR
HISTOGRAM
MAX9934F GAIN ERROR DRIFT
HISTOGRAM
OUT
V
= GND
REF
40
35
30
25
20
15
10
5
25
20
15
10
5
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
GAIN = 25µA/mV
GAIN = 5µA/mV
UNIDIRECTIONAL
0
0
0
10 20 30 40 50 60 70 80
(mV)
V
SENSE
GE (%)
TC GE (PPM/°C)
Maxim Integrated
5
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
Typical Operating Characteristics (continued)
(V = 3.3V, V
= V
= 3.0V, V
= 0V, C = 1000pF, R
= 10kΩ to GND for unidirectional operation, R
= 10kΩ to
CC
RS+
RS-
SENSE
L
OUT
OUT
V
CC
/2 for bidirectional operation. T = +25°C, unless otherwise noted.)
A
V
vs. V
SENSE
OUT
V
= 1.65V
V
OUT
vs. V (V < 5mV)
SENSE OUT
REF
2.0
1.5
1.0
0.5
0
5
4
3
2
1
0
BIDIRECTIONAL
G = 25FA/mV
GAIN = 5µA/mV
G = 5FA/mV
GAIN = 25µA/mV
-0.5
-1.0
-1.5
-2.0
-40
-20
0
20
40
0
20
40
60
80
100
V
(mV)
VSENSE + VOS (FV)
SENSE
SUPPLY CURRENT
V
OH
vs. I
OH
vs. TEMPERATURE (V = 0)
CS
160
140
120
100
80
300
250
200
150
100
50
V
= 0V
CM
MAX9934F
V
= 5.5V
CM
MAX9934T
60
0
40
0
100
200
I
300
(µA)
400
500
600
-40 -25 -10
5
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
OH
SUPPLY CURRENT
vs. TEMPERATURE
RS+ BIAS CURRENT
vs. V
RS+
160
140
120
100
80
10nA
1nA
V
= 0V
CM
T
A
= +125°C
V
= 5.5V
CM
100pA
10pA
1pA
T
= +25°C AND -40°C
A
60
40
-40 -25 -10
5
20 35 50 65 80 95 110 125
-0.1 0.6 1.3 2.0 2.7 3.4 4.1 4.8 5.5
(V)
TEMPERATURE (°C)
V
RS+
6
Maxim Integrated
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
Typical Operating Characteristics (continued)
(V = 3.3V, V
= V
= 3.0V, V
= 0V, C = 1000pF, R
= 10kΩ to GND for unidirectional operation, R = 10kΩ to
OUT
CC
RS+
RS-
SENSE
L
OUT
V
CC
/2 for bidirectional operation. T = +25°C, unless otherwise noted.)
A
RS- BIAS CURRENT
RS- BIAS CURRENT
vs. V (-0.1V ≤ V ≤ V )
vs. V ( 3V ≤ V
≤ 5.5V)
RS-
RS-
CC
RS-
RS_
50
45
40
35
30
25
20
15
10
5
100nA
10nA
1nA
T
= +125°C
A
T
= +125°C
A
T
= +25°C
A
T
= -40°C
A
100pA
10pA
1pA
T
= +25°C AND -40°C
A
0
-0.1 0.4 0.9 1.4 1.9 2.4 2.9 3.4
(V)
3.0
3.5
4.0
4.5
5.0
5.5
V
V
(V)
RS-
RS-
OUTPUT LEAKAGE CURRENT
vs. V (V = 0)
OUTPUT LEAKAGE CURRENT
vs. V
(V = 0, V = 0)
OUT CS
OUT CC
CS
10nA
1nA
10nA
T
= +125°C
A
1nA
100pA
10pA
1pA
T
= +125°C
= +25°C
A
T
100pA
10pA
1pA
A
T
= +25°C
A
T
= -40°C
A
T
= -40°C
A
100fA
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
(V)
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
(V)
V
V
OUT
OUT
NORMALIZED GAIN
vs. FREQUENCY
COMMON-MODE REJECTION RATIO
vs. FREQUENCY
10
0
0
-20
G = 5FA/mV
-40
-10
-20
-30
-40
G = 25FA/mV
-60
-80
-100
-120
-140
1
10
100
1k
10k
100k
0.01
0.1
1.0
10
100
FREQUENCY (Hz)
FREQUENCY (kHz)
Maxim Integrated
7
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
Typical Operating Characteristics (continued)
(V = 3.3V, V
= V
= 3.0V, V
= 0V, C = 1000pF, R
= 10kΩ to GND for unidirectional operation, R
= 10kΩ to
CC
RS+
RS-
SENSE
L
OUT
OUT
V
CC
/2 for bidirectional operation. T = +25°C, unless otherwise noted.)
A
OUTPUT SETTING TIME
vs. PERCENTAGE OF FINAL VALUE
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
1V V
STEP
OUT
-20
-40
MAX9934T
-60
MAX9934F
-80
-100
-120
1.00
0.10
0.01
0.01
0.1
1.0
10
100
PERCENTAGE OF FINAL VALUE (%)
FREQUENCY (kHz)
LARGE-SIGNAL INPUT STEP
RESPONSE (MAX9934F)
LARGE-SIGNAL INPUT STEP
RESPONSE (MAX9934T)
MAX9934 toc24
MAX9934 toc25
V
V
SENSE
SENSE
20mV/div
5mV/div
0.01% FINAL VALUE
1% FINAL VALUE
0.01% FINAL VALUE
1% FINAL VALUE
2V
2V
V
V
OUT
OUT
1V
1V
500mV/div
500mV/div
100µs/div
400µs/div
CS DISABLED TRANSIENT RESPONSE
OUTPUT SELECT TIME
C
= 10pF (MAX9934T)
OUT
MAX9934 toc26
MAX9934 toc27
C = 0
L
V
CS
V
1% FINAL VALUE
2V/div
CS
2V/div
1V
V
OUT
0.1% FINAL VALUE
1% FINAL VALUE
500mV/div
MAX9934T
MAX9934F
1V
V
OUT
V
OUT
0.1% FINAL VALUE
500mV/div
1V/div
40Fs/div
4µs/div
8
Maxim Integrated
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
Typical Operating Characteristics (continued)
(V = 3.3V, V
= V
= 3.0V, V
= 0V, C = 1000pF, R
= 10kΩ to GND for unidirectional operation, R
= 10kΩ to
CC
RS+
RS-
SENSE
L
OUT
OUT
V
CC
/2 for bidirectional operation. T = +25°C, unless otherwise noted.)
A
SATURATION RECOVERY TIME
POWER-UP TIME
V
OUT
= V TO 1V (MAX9934T)
OL
MAX9934 toc29
MAX9934 toc28
UNIDIRECTIONAL
V
CS
2V/div
V
SENSE
1% FINAL VALUE
5mV/div
1mV
1V
1V
0.1% FINAL VALUE
1% FINAL VALUE
V
OUT
500mV/div
MAX9934T
MAX9934F
1V
0V
V
OUT
500mV/div
0.1% FINAL VALUE
V
OUT
500mV/div
C
= 0.1µF
BYPASS
100Fs/div
400Fs/div
SATURATION RECOVERY TIME
= V TO 1V (MAX9934T)
V
OUT
OH
MAX9934 toc30
UNIDIRECTIONAL
V
SENSE
10mV/div
V
OUT
1V/div
1V
400µs/div
Maxim Integrated
9
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
Pin Description
PIN/BUMP
NAME
FUNCTION
UCSP
µMAX
A1
1
V
Power Supply
Current Output. OUT provides an output current proportional to input V
CC
. Connect an
SENSE
A2
2
OUT
external resistor (R ) from OUT to GND for unidirectional sensing or to an external reference
OUT
voltage for bidirectional sensing.
A3
B1
B2
3
8
7
GND
RS+
RS-
Ground
Sense Resistor Power Side Connection
Sense Resistor Load Side Connection
Chip-Select Input. Drive CS high to enable OUT, drive CS low to put OUT in a high-impedance
state.
B3
—
6
CS
4, 5
N.C.
No Connection. Not internally connected.
Functional Diagram
V
SENSE
CS
MAX9934
% FINAL VALUE
V
CC
2V
V
OUT
1V STEP
RS+
RS-
% FINAL VALUE
G
m
*R
GAIN
G
m
1V
OUT
t
t
S
S
GND
*R
R
= 40Ω FOR THE MAX9934T AND
= 200Ω FOR THE MAX9934F.
GAIN
GAIN
Figure 1. Output Settling Time
achieve gain error of less than 0.25%. The precision V
OS
Detailed Description
specification allows accurate current measurements with
a low-value current-sense resistor, thus reducing power
dissipation in battery-powered systems, as well as load-
regulation issues in low-voltage DC power supplies.
The MAX9934 high-side, current-sense amplifier moni-
tors current through an external current-sense resistor
by amplifying the voltage across the resistor (V
)
SENSE
). An output voltage
to create an output current (I
OUT
The MAX9934 high-side current-sense amplifier fea-
tures a -0.1V to +5.5V input common-mode range that
is independent of supply voltage (V ). This ability to
CC
sense at voltages beyond the supply rail allows the
monitoring of currents out of a power supply even in a
shorted condition, while also enabling high-side current
sensing at voltages greater than the MAX9934 supply
(V
) then develops across the external output resis-
OUT
tor (R
). See the Typical Operating Circuit.
OUT
The MAX9934 uses precision amplifier design tech-
niques to achieve a low-input offset voltage of less than
10µV. These techniques also enable extremely low-input
offset voltage drift over time and temperature and
10
Maxim Integrated
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
1.8V
3.3V
V
CS
V
CC
2.5V
0V
0V
% FINAL VALUE
% FINAL VALUE
t
t
HZ
PD
V
OUT
V
OUT
100mV
100mV
t
PU
t
ZH
Figure 2. Output Select and Deselect Time
Figure 3. Output Power-Up and Power-Down Time
voltage. Further, when V
= 0, the amplifier maintains
CC
Applications Information
an extremely high impedance on both its inputs and
output, up to the maximum operating voltages (see the
Absolute Maximum Ratings section).
Advantages of Current-Output
Architecture
The transconductance transfer function of the MAX9934
converts input differential voltage to an output current.
The MAX9934 features a CS that can be used to dese-
lect its output current-source. This allows multiple cur-
rent-sense amplifier outputs to be multiplexed into a
single ADC channel with a single R
Select Functionality for Multiplexed Systems section for
more details.
An output termination resistor, R
, then converts this
OUT
current to a voltage. In a large circuit board with multi-
ple ground planes and multiple current-measurement
rails spread across the board, traditional voltage-output
current-sense amplifiers become susceptible to
ground-bounce errors. These errors occur because the
local ground at the location of the current-sense amplifi-
er is at a slightly different voltage than the local ground
voltage at the ADC that is sampling the voltage. The
MAX9934 allows accurate measurements to be made
even in the presence of system ground noise. This is
achieved by sending the output information as a cur-
rent, and by terminating to the ADC ground.
. See the Chip
OUT
The Functional Diagram shows the internal operation of
the MAX9934. At its core is the indirect current-feed-
back architecture. This architecture uses two matched
transconductance amplifiers to convert their input dif-
ferential voltages into an output current. A high-gain
feedback amplifier forces the voltage drop across
R
to be the same as the input differential voltage.
GAIN
The internal resistor (R
) sets the transconductance
GAIN
gain of the device. Both input and output transconduc-
tance amplifiers feature excellent common-mode rejec-
tion characteristics, helping the MAX9934 to deliver
industry-leading precision specifications over the full
common-mode range.
A further advantage of current-output systems is the
flexibility in setting final voltage gain of the device.
Since the final voltage gain is user-controlled by the
choice of output termination resistor, it is easy to opti-
mize the monitored load current range to the ADC input
voltage range. It is no longer necessary to increase the
size of the sense resistor (also increasing power dissi-
pation) as necessary with fixed-gain, voltage-output
current-sense amplifiers.
Maxim Integrated
11
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
I
LOAD1
V
= 3.3V
CC
0.1µF
-0.1V ≤ V ≤ 5.5V
V
IN1
CM
R
SENSE
OUT1
MAX9934
MICROCONTROLLER
CS1
I
LOAD2
V
= 3.3V
CC
0.1µF
V
IN2
-0.1V ≤ V ≤ 5.5V
CM
R
SENSE
OUT2
MAX9934
CS2
I
LOAD3
V
= 3.3V
CC
0.1µF
-0.1V ≤ V ≤ 5.5V
V
IN3
CM
R
SENSE
OUT3
MAX9934
CS3
ADC
V
OUT
UNIDIRECTIONAL OPERATION
10kΩ
(OPTIONAL)
Figure 4. Typical Application Circuit Showing Chip-Select Multiplexing
amplifier outputs are connected in common to a single
load resistor located adjacent to the monitoring ADC.
This resistor is terminated to the ADC ground reference
as shown in Figure 4 for unidirectional applications.
Chip-Select Functionality
for Multiplexed Systems
The MAX9934 features a CS that can be used to dese-
lect the output current - source achieving a high-imped-
ance output with 0.1nA leakage current. Thus, different
supply voltages can be used to power different
MAX9934 devices that are multiplexed on the same
bus. This technique makes it possible for advanced
current monitoring and power-management schemes to
be implemented when a limited number of ADC chan-
nels are available.
Figure 5 shows a bidirectional multiplexed application.
Terminating the external resistor at the ground refer-
ence of the ADC minimizes errors due to ground shift
as discussed in the Advantages of Current-Output
Architecture section.
The MAX9934 is capable of both sourcing and sinking
current from OUT, and thus can be used as a precision
bidirectional current-sense amplifier. To enable this
In a multiplexed arrangement, each MAX9934 is typi-
cally placed near the load being monitored and all
functionality, terminate R
to a midrail voltage V
.
OUT
BIAS
12
Maxim Integrated
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
I
LOAD1
V
= 3.3V
CC
-0.1V ≤ V ≤ 5.5V
V
CM
IN1
R
SENSE
OUT1
MAX9934
MICROCONTROLLER
CS1
CS
I
LOAD2
V
= 3.3V
CC
-0.1V ≤ V ≤ 5.5V
V
IN2
CM
R
SENSE
OUT2
MAX9934
CS
CS2
I
LOAD3
V
= 3.3V
CC
-0.1V ≤ V ≤ 5.5V
V
IN3
CM
R
SENSE
OUT3
MAX9934
CS3
CS
TO EXTERNAL
REFERENCE
VOLTAGE
R
V
OUT
V
REF
R
2
R
OUT
=
10kΩ
ADC
R
10kΩ
(OPTIONAL)
Figure 5. Bidirectional Multiplexed Operation
In Figure 5, V
is equal to V
when the sum of all
Since the ADC reference voltage, V
, determines the
OUT
BIAS
REF
outputs is zero. For positive input-sense voltages, the
MAX9934 sources current causing its output voltage to
full-scale reading, a common choice for V
is
BIAS
V
/2. The current output makes it possible to use a
REF
rise above V
. For negative input-sense voltages,
simple resistor-divider from V
to GND to generate
REF
BIAS
the MAX9934 sinks current causing its output voltage to
V
. The output resistance for gain calculation is the
BIAS
be lower than V
sensing.
, thus allowing bidirectional current
BIAS
parallel combination of the two resistors. For example, if
two equal value resistors, R, are used to generate a
V
= V
/2, the output termination resistance for
REF
BIAS
gain calculation is R
= R/2. See Figure 5.
OUT
Maxim Integrated
13
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
A MAX9934 can be deselected by either forcing V
low as shown in Figures 4 and 5, or by making V
Choosing R
SENSE
and R
OUT
CS
=
In the current-sense application, the monitored load
current (I ) develops a sense voltage (V
CC
0V as shown in Figure 6. In all these conditions, the
MAX9934 maintains a high-impedance output with
0.1nA (typ) leakage current. In this state, OUT can rise
)
SENSE
). The
LOAD
across a current-sense resistor (R
SENSE
MAX9934 sources or sinks an output current that is pro-
portional to V . Finally, the MAX9934 output cur-
above V
if necessary. Thus, different supply voltages
CC
SENSE
can be used to power different MAX9934 devices that
are multiplexed on the same OUT bus. Multiplexing by
rent is provided to an output resistor (R
) to develop
OUT
an output voltage across R
the sensed load current.
that is proportional to
OUT
forcing the MAX9934 to be powered down (V
= 0V)
CC
reduces its supply current to zero to help extend bat-
tery life in portable applications.
V
CC
= 3.3V
1/4 MAX4737
I
LOAD1
0.1µF
V
IN1
V
IN2
V
IN3
-0.1V ≤ V ≤ 5.5V
CM
R
SENSE
CS
OUT1
MAX9934
MICROCONTROLLER
CS1
V
= 3.3V
CC
1/4 MAX4737
I
LOAD2
0.1µF
-0.1V ≤ V ≤ 5.5V
CM
R
SENSE
CS
OUT2
MAX9934
CS2
V
= 3.3V
CC
1/4 MAX4737
I
LOAD3
0.1µF
-0.1V ≤ V ≤ 5.5V
CM
R
SENSE
CS
OUT3
MAX9934
CS3
ADC
R
OUT
10kΩ
(OPTIONAL)
Figure 6. Multiplexed Amplifiers with Power Saving
14
Maxim Integrated
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
Three components are to be selected to optimize the
Table 1. Unidirectional Gain Table*
current-sense system: R
, R
, and the
OUT
SENSE
OUTPUT
CURRENT
(µA)
MAX9934 gain option (G = 25µA/mV or 5µA/mV).
M
V
R
(kΩ)
GAIN
(V/V)
SENSE
(mV)
OUT
PART
Tables 1 and 2 are gain tables for unidirectional and
bidirectional operation, respectively. They offer a few
examples for both MAX9934 options having an output
range of 3.1V unidirectional and 1.65V bidirectional.
12.4
24.8
62
310
620
310
375
10
5
250
125
50
MAX9934T
MAX9934F
Note that the output current of the MAX9934 adds to its
quiescent current. This can be calculated as follows:
10
8
75
40
I
= V
/R
OUT,MAX
OUT,MAX OUT
*All calculations were made with V
= 3.3V and V
=
CC
OUT(MAX)
When selecting R
LOAD
power dissipation in R
, consider the expected magni-
SENSE
and the required V
V
CC
- V
= 3.1V.
OH
tude of I
to manage
SENSE
:
SENSE
Table 2. Bidirectional Gain Table*
R
= V
/I
SENSE
SENSE,MAX LOAD,MAX
OUTPUT
CURRENT
(µA)
R
is typically a low-value resistor specifically
SENSE
V
R
OUT
(kΩ)
SENSE
(mV)
PART
GAIN (V/V)
designed for current-sense applications.
Finally, in selecting the appropriate MAX9934 gain option
(G ), consider both the required V
and I
:
M
SENSE
OUT
5.8
11.6
24
145
290
600
145
290
360
10
5
250
125
60
G
M
= I
/V
OUT,MAX SENSE,MAX
MAX9934T
MAX9934F
Once all three component values have been selected in
the current-sense application, the system performance
is represented by:
2.4
10
5
29
50
58
25
V
= R
x I
SENSE
SENSE LOAD
72
4
20
and
x G x R
OUT
*All calculations were made with V = 3.3V, V
= V
-
CC
OUT(MAX)
CC
V
OH
= 3.1V, V
= V , and OUT connected to an exter-
V
OUT
= V
OUT(MIN) OL
SENSE
M
nal reference voltage of V
= 1.65V through R
.
REF
OUT
Accuracy
In a first-order analysis of accuracy there are two
MAX9934 specifications that contribute to output error,
Interfacing the MAX9934 to SAR ADCs
Since the MAX9934 is essentially a high-output imped-
ance current-source, its output termination resistor,
input offset (V ) and gain error (GE). The MAX9934 has
OS
a maximum V of 10µV and a maximum GE of 0.25%.
OS
R
, acts like a source impedance when driving an
OUT
Note that the tolerance and temperature coefficient of
the chosen resistors directly affect the precision of any
measurement system.
ADC channel. Most successive approximation register
(SAR) architecture ADCs specify a maximum source
resistance to avoid compromising the accuracy of their
Efficiency and Power Dissipation
readings. Choose the output termination resistor R
OUT
At high-current levels, the I2R losses in R
can be
such that it is less than that required by the ADC speci-
is larger than the
SENSE
significant. Take this into consideration when choosing
the resistor value and its power dissipation (wattage)
rating. Also, the sense resistor’s value drifts if it is
fication (10kΩ or less). If the R
OUT
source resistance specified, the ADC internal sampling
capacitor can momentarily load the amplifier output
and cause a drop in the voltage reading.
allowed to self-heat excessively. The precision V
of
OS
the MAX9934 allows the use of a small sense resistor to
reduce power dissipation and eliminate hot spots.
If R
is larger than the source resistance specified,
OUT
consider using a ceramic capacitor from ADC input to
GND. This input capacitor supplies momentary charge
to the internal ADC sampling capacitor, helping hold
Kelvin Contacts
Due to the high currents that flow through R
, take
SENSE
V
constant to within 1/2 LSB during the acquisition
OUT
care to prevent trace resistance in the load current path
from causing errors in the sense voltage. Use a four ter-
minal current-sense resistor or Kelvin contacts (force
and sense) PCB layout techniques.
period. Use of this capacitor reduces the noise in the
output signal to improve sensitivity of measurement.
Maxim Integrated
15
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
Effect of Input-Bias Currents
The MAX9934 has extremely low CMOS input-bias cur-
rents at both RS+ and RS- (0.1nA) when the input com-
mon-mode voltage is less than the supply voltage.
When the input common-mode voltage becomes higher
BUCK
CONTROLLER
ASIC
than the supply voltage, it draws the input stage operat-
ing current from RS-, 35µA (typ). RS+ maintains its
CMOS input characteristics.
Low-input-bias currents are extremely useful in design
of input filters for current-sense amplifiers. Input differ-
ential filters are sometimes required to average out
RS+
RS-
rapidly varying load currents. An example of such load
currents are those consumed by a processor, or
switching power supply. Large bias and offset currents
can interact with resistors used in these external filters
to generate large input offset voltages and gain errors.
For more detailed information, see Application Note
AN3888: Performance of Current-Sense Amplifiers with
Input Series Resistors.
MAX9934
Due to the low-input-bias currents, resistors as large as
10kΩ can be easily used without impact on error speci-
fications with the MAX9934. For applications where the
input common-mode voltage is below V , a balanced
CC
Figure 7. One-Sided Input Filter
differential filter can be used. For applications where
the input common-mode voltage extends above V
,
CC
use a one-sided filter with a capacitor between RS+
and RS-, and a filter resistor in series with RS+ to main-
tain the excellent performance of the MAX9934. See
Figure 7.
acteristics. Extending the useful output below 1mV
makes it possible for the MAX9934 to accurately moni-
tor very low currents.
Use as Precision
PCB Layout
For applications where the input common-mode voltage
Instrumentation Amplifier
When the input common-mode voltage is below V
,
CC
extends above V , trace resistance between R
CC
SENSE
error due to the
the input bias current of the RS- input drops to the
10pA range, the same range as the RS+ input. This
low-input-bias current in combination with the rail-to-rail
common-mode input range, the extremely high com-
and RS- influences the effective V
OS
voltage drop developed across the trace resistance by
the 35µA input bias current at RS-.
mon-mode rejection, and low V
of the MAX9934
OS
Monitoring Very Low Currents
The accuracy of the MAX9934 leads to a wide dynamic
range. This applies to both unidirectional mode and
bidirectional mode. This is made possible in the unidi-
rectional mode because the output maintains gain
make it ideally suited for use as a precision instrumen-
tation amplifier. In addition, the MAX9934 is stable into
an infinite capacitive load, allowing filtering flexibility.
Figure 8 shows the MAX9934 in a multiplexed arrange-
ment of strain-gauge amplifiers.
accuracy below 1mV as shown in the V
OUT
vs. V
SENSE
OUT
(V
< 5mV) graph in the Typical Operating Char-
16
Maxim Integrated
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
V
= 3.3V
CC
0.1µF
OUT1
V
IN1
MAX9934
CS
CS1
V
= 3.3V
CC
0.1µF
MICROCONTROLLER
OUT2
MAX9934
V
IN2
CS
CS2
V
= 3.3V
CC
0.1µF
OUT3
V
MAX9934
IN3
CS
CS3
TO EXTERNAL
REFERENCE
VOLTAGE
R
V
REF
10kΩ
R
= R/2
OUT
ADC
V
OUT
R
10kΩ
(OPTIONAL)
Figure 8. Multiplexed, Strain-Gauge Amplifier Operation
Maxim Integrated
17
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
Pin Configurations
TOP VIEW
(BUMPS ON BOTTOM)
TOP VIEW
MAX9934T/F
+
+
V
1
2
3
4
8
7
6
5
RS+
RS-
CS
CC
RS+
RS-
B1
A1
A2
A3
V
CC
OUT
GND
N.C.
MAX9934T/F
OUT
GND
B2
B3
N.C.
CS
µMAX
UCSP
Chip Information
Package Information
For the latest package outline information and land patterns (foot-
prints), go to www.maximintegrated.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.
PROCESS: BiCMOS
LAND
PATTERN NO.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE NO.
—
2x3 UCSP
8 µMAX
R61A1+1
U8+1
21-0228
21-0036
90-0092
18
Maxim Integrated
MAX9934
High-Precision, Low-Voltage, Current-Sense Amplifier
with Current Output and Chip Select for Multiplexing
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
1
2
3
10/09
1/10
Initial release
—
1–10, 18
1, 2
Removed µDFN package option
4/10
Removed future product references and updated lead temperature
11/12
Added automotive packages to Ordering Information
1
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent
licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and
max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000 ________________________________ 19
© 2012 Maxim Integrated Products, Inc.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
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