MAXIM MAX9928FABTT

19-4251; Rev 2; 4/11
KIT
ATION
EVALU
E
L
B
A
IL
AVA
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
The MAX9928/MAX9929 low-cost, uni-/bidirectional,
high-side, current-sense amplifiers are ideal for monitoring battery charge and discharge currents in notebooks, cell phones, and other portable equipment.
These devices feature a wide -0.1V to +28V input common-mode voltage range, low 20µA supply current with
VOS less than 0.4mV, and a gain accuracy better than
1.0%. The input common-mode range is independent
of the supply voltage, ensuring that the current-sense
information remains accurate even when the measurement rail is shorted to ground.
The MAX9928F features a current output with a transconductance ratio of 5µA/mV. An external resistor converts
the output current to a voltage, allowing adjustable gain
so that the input sense voltage can be matched to the
maximum ADC input swing. The MAX9929F has a voltage
output and integrates a 10kΩ output resistor for a fixed
voltage gain of 50V/V.
A digital SIGN output indicates direction of current flow,
so the user can utilize the full ADC input range for measuring both charging and discharging currents.
The MAX9928/MAX9929 are fully specified over the -40°C
to +125°C automotive temperature range, and available
in 6-bump UCSP™ (1mm x 1.5mm) and 8-pin µMAX®
packages. The UCSP package is bump-to-bump compatible with the MAX4372_EBT.
Features
o Wide -0.1V to +28V Common-Mode Range,
Independent of Supply Voltage
o 2.5V to 5.5V Operating Supply Voltage
o 20µA Quiescent Supply Current
o 0.4mV (max) Input Offset Voltage
o Gain Accuracy Better than 1% (max)
o SIGN Output Indicates Current Polarity
o Transconductance and Gain Versions Available
5µA/mV (MAX9928F)
50V/V (MAX9929F)
o Pin Compatible with the MAX4372 in UCSP
o Available in Ultra-Small, 3x2 UCSP
(1mm x 1.5mm) and 8-Pin µMAX Packages
Applications
Monitoring Charge/Discharge Currents in
Portable/Battery-Powered Systems
Notebook Computers
General-System/Board-Level Current Monitoring
Smart-Battery Packs/Chargers
Precision Current Sources
UCSP is a trademark and µMAX is a registered trademark of
Maxim Integrated Products, Inc.
Smart Cell Phones
Super Capacitor Charge/Discharge
Pin Configurations and Typical Operating Circuit appear at
end of data sheet.
Ordering Information
PART
OUTPUT TYPE
GAIN
Current
Gm = 5µA/mV
8 µMAX
MAX9928FABT+T *
Current
Gm = 5µA/mV
3x2 UCSP
MAX9929FAUA+
Voltage
AV = 50V/V
8 µMAX
MAX9929FABT+T *
Voltage
AV = 50V/V
3x2 UCSP
MAX9928FAUA+
PIN-PACKAGE
TOP MARK
—
+AAF
—
+ADI
Note: All devices are specified over the -40°C to +125°C operating temperature range.
+Denotes a lead-free/RoHS-compliant package.
T = Tape and reel.
*The MAX9928FABT and the MAX9929FABT use Package Code R61A1+1 with backside coating to minimize die chipping.
________________________________________________________________ Maxim Integrated Products
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
MAX9928/MAX9929
General Description
MAX9928/MAX9929
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
ABSOLUTE MAXIMUM RATINGS
VCC, SIGN to GND ...................................................-0.3V to +6V
RS+, RS- to GND....................................................-0.3V to +30V
OUT to GND ...............................................-0.3V to (VCC + 0.3V)
Differential Input Voltage (VRS+ - VRS-) .............................. ±30V
OUT, SIGN Short Circuit to VCC or GND ...................Continuous
Current into Any Pin..........................................................±20mA
Continuous Power Dissipation (TA = +70°C)
6-Bump 1mm x 1.5mm UCSP
(derate 3.9mW/°C above +70°C) ............................308.3mW
8-Pin µMAX (derate 4.8mW/°C above +70°C) .............388mW
Operating Temperature Range ........................-40°C to +125°C
Storage Temperature Range ............................-65°C to +150°C
Junction Temperature .....................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
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
(VRS+ = -0.1V to +28V, VCC = 3.3V, VSENSE = (VRS+ - VRS-) = 0V, ROUT = 10kΩ for MAX9928F, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
±0.1
±0.4
UNITS
AMPLIFIER DC ELECTRICAL CHARACTERISTICS
VRS+ = 3.6V
Input Offset Voltage (Note 2)
VOS
VRS+ = -0.1V
Common-Mode Input Range
VCMR
TA = +25°C
TA = -40°C to +125°C
TA = +25°C
±0.6
TA = -40°C to +125°C
(Note 3)
2V ≤ VRS+ ≤ 28V
±0.8
±1.0
mV
±3.0
-0.1
TA = +25°C
93
TA = -40°C to +125°C
87
TA = +25°C
60
TA = -40°C to +125°C
54
+28
V
104
Common-Mode Rejection Ratio
CMRR
Full-Scale Sense Voltage (Note 2)
VSENSE
MAX992_F
±50
mV
AV
MAX9929F
50
V/V
Gain (Note 2)
-0.1V ≤ VRS+ ≤
+2V
MAX9929F,
VRS+ = 3.6V
Gain Accuracy (Notes 2, 6)
MAX9929F,
VRS+ = -0.1V
Transconductance (Note 2)
GM
Transconductance Accuracy
(Note 2)
Input Bias Current (Note 4)
Input Offset Bias Current (Note 4)
Input Leakage Current
2
IRS+, IRSIOS
IRS+, IRS-
TA = +25°C
±0.3
±1.0
±0.3
±1.0
TA = -40°C to +125°C
±2.5
TA = +25°C
TA = -40°C to +125°C
MAX9928F,
VRS+ = 3.6V
MAX9928F,
VRS+ = -0.1V
TA = +25°C
5
±0.3
±0.3
TA = -40°C to +125°C
2V ≤ VRS+ ≤ 28V
-0.1V ≤ VRS+ ≤ +2V
%
±2.8
MAX9928F
TA = +25°C
TA = -40°C to +125°C
dB
72
µA/mV
±1.0
±2.5
±1.0
%
±2.8
0
1.6
-80
6
+6
2V ≤ VRS+ ≤ 28V
±0.05
±1
-0.1V ≤ VRS+ ≤ +2V
±0.2
±2
VCC = 0V, VRS+ = VRS- = 28V (Note 5)
0.05
1.0
_______________________________________________________________________________________
µA
µA
µA
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
(VRS+ = -0.1V to +28V, VCC = 3.3V, VSENSE = (VRS+ - VRS-) = 0V, ROUT = 10kΩ for MAX9928F, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
Output Resistance
SYMBOL
ROUT
Output High Voltage (Note 6)
CONDITIONS
MIN
MAX9928F
TYP
MAX
5
MAX9929F
6.4
UNITS
MΩ
10
13.6
MAX9928F, ROUT = 10kΩ
(VCC 0.1)
(VCC 0.45)
MAX9929F
(VCC 0.1)
(VCC 0.45)
TA = +25°C
TA = -40°C to +125°C
0.25
2.0
15
TA = +25°C
0.025
0.2
kΩ
V
VOH
Minimum Output Voltage (Note 7)
VOL
MAX9929F
Minimum Output Current (Note 7)
IOL
MAX9928F
TA = -40°C to +125°C
1.5
mV
µA
SIGN COMPARATOR DC ELECTRICAL CHARACTERISTICS
Discharge to Charge Trip Point
(Note 8)
VRS+ = 3.6V
VTDC
VRS+ = -0.1V
Charge to Discharge Trip Point
(Note 8)
VTCD
Hysteresis Width
VHYS
Common-Mode Input Range
(Note 9)
VCMR
Common-Mode Rejection Ratio
(Note 9)
CMRR
Output Low Voltage
VOL
Output High Voltage
Internal Pullup Resistor
VRS+ = 3.6V
VRS+ = -0.1V
VRS+ = 3.6V,
-0.1V
TA = +25°C
TA = -40°C to +125°C
-1.6
-2.15
-1.2
-0.5
-0.15
TA = +25°C
-2.5
-1.2
+0.25
TA = -40°C to +125°C
-4.6
mV
+2.3
TA = +25°C
TA = +25°C
-1.8
-1.8
mV
TA = +25°C
0.6
mV
-0.1
+28
2V ≤ VRS+ ≤ 28V
102
-0.1V ≤ VRS+ ≤ +2V
74
ISINK = 100µA
V
dB
0.03
0.1
V
VOH
(VCC 0.01)
(VCC 0.04)
V
RPULL-UP
1
MΩ
POWER SUPPLY
Supply Voltage Range (Note 10)
VCC
Amplifier Power-Supply Rejection
Ratio (Note 10)
PSRRA
Comparator Power-Supply
Rejection Ratio
PSRRC
Quiescent Supply Current
ICC
TA = +25°C
2.5
5.5
TA = -40°C to +125°C
2.8
5.5
VRS+ = 3.6V
72
90
VRS+ = -0.1V
66
86
VRS+ = 3.6V
90
VRS+ = -0.1V
86
V
dB
dB
2V ≤ VRS+ ≤ 28V
20
30
-0.1V ≤ VRS+ < +2V
115
200
µA
_______________________________________________________________________________________
3
MAX9928/MAX9929
ELECTRICAL CHARACTERISTICS (continued)
MAX9928/MAX9929
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(VRS+ = -0.1V to +28V, VCC = 3.3V, VSENSE = (VRS+ - VRS-) = 0V, ROUT = 10kΩ for MAX9928F, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
AC ELECTRICAL CHARACTERISTICS
-3dB Bandwidth
BW
MAX992_F, VSENSE = 50mV
MAX992_F, VSENSE =
5mV to 50mV step
OUT Settling to 1% of Final Value
tSET
VRS+ = 3.6V,
CLOAD = 10pF,
ROUT = 10kΩ for MAX992_F, VSENSE =
MAX9928F
50mV to 5mV step
150
kHz
6
µs
15
Overdrive = 1mV
80
Overdrive = 5mV
30
Overdrive = 1mV
50
Overdrive = 5mV
13
Power-Up Time to 1% of Final
Value
VSENSE = 50mV for MAX992_F,
VRS+ = 3.6V, CLOAD = 10pF
50
µs
Saturation Recovery Time
100mV ≤ VSENSE ≤ 50mV for MAX992_F,
VRS+ = 3.6V, CLOAD = 10pF
4
ms
SIGN Comparator Propagation
Delay (Low to High)
tPROP_LH
SIGN Comparator Propagation
Delay (High to Low)
tPROP_HL
µs
µs
Note 1: All devices are 100% production tested at TA = +25°C. All temperature limits are guaranteed by design.
Note 2: VOS is extrapolated from two point transconductance and gain accuracy tests. Measurements are made at VSENSE =
+5mV and VSENSE = +50mV for MAX992_F. These measurements are also used to test the full-scale sense voltage,
transconductance, and gain. These VOS specifications are for the trimmed direction only (VRS+ > VRS-). For current flowing
in the opposite direction (VRS- > VRS+), VOS is ±1mV (max) at +25°C and ±1.8mV (max) over temperature, when VRS+ is at
3.6V. See the Detailed Description for more information.
Note 3: Guaranteed by common-mode rejection ratio. Extrapolated VOS as described in Note 2 is used to calculate common-mode
rejection ratio.
Note 4: Includes input bias current of SIGN comparator.
Note 5: Leakage in to RS+ or RS- when VCC = 0V. Includes input leakage current of SIGN comparator. This specification does not
add to the bias current.
Note 6: Output voltage should be 650mV below VCC to achieve full accuracy.
Note 7: IOL is the minimum output current in the VSENSE - IOUT transfer characteristics. VOL is the minimum output voltage in the
VSENSE - VOUT transfer characteristic.
Note 8: VSENSE voltage required to switch comparator.
Note 9: Discharge to charge trip point is functionally tested at VCM = -0.1V, +3.6V, and +28V.
Note 10: Guaranteed by PSRR test. Extrapolated VOS as described in Note 2 is used to calculate the power-supply rejection ratio.
VSENSE has to be such that the output voltage is 650mV below VCC to achieve full accuracy.
4
_______________________________________________________________________________________
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
20
FREQUENCY (%)
25
20
15
1.5
OFFSET VOLTAGE (mV)
25
15
10
MAX9928 toc03
AV = 50V/V
30
2.0
MAX9928 toc02
AV = 50V/V
35
FREQUENCY (%)
30
MAX9928 toc01
45
40
OFFSET VOLTAGE
vs. COMMON-MODE VOLTAGE
GAIN ACCURACY
HISTOGRAM
VOS HISTOGRAM
1.0
0.5
0
-0.5
-1.0
10
5
5
0
-1.5
-2.0
0
-0.40 -0.30 -0.20 -0.10 0
0.10
0.20 0.30 0.40
-1
-1.0 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0
GAIN ACCURACY (%)
0
1
2
28
3
COMMON-MODE VOLTAGE (V)
VOS (mV)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
VSENSE = 0V
125
SUPPLY CURRENT (μA)
0.6
0.4
0.2
0
-0.2
-0.4
VRS+ = 0V
100
75
50
150
120
VRS+ = 3.6V
-0.6
90
VCC = 5.5V
60
VCC = 2.5V
30
25
-0.8
-1.0
0
-40 -25 -10 5 20 35 50 65 80 95 110 125
0
2.5
TEMPERATURE (°C)
3.0
3.5
4.0
4.5
5.5
5.0
0
0.5
1.0
1.5
2.0
28
COMMON-MODE VOLTAGE (V)
INPUT BIAS CURRENT
vs. COMMON-MODE VOLTAGE
VRS+ = 0V
100
75
50
VRS+ = 3.6V
25
10
MAX9928 toc08
VSENSE = 0V
0
INPUT BIAS CURRENT (μA)
MAX9928 toc07
150
125
-0.5
SUPPLY VOLTAGE (V)
SUPPLY CURRENT
vs. TEMPERATURE
SUPPLY CURRENT (μA)
OFFSET VOLTAGE (mV)
150
SUPPLY CURRENT (μA)
VCM = 3.6V
MAX9928 toc05
0.8
MAX9928 toc04
1.0
SUPPLY CURRENT
vs. COMMON-MODE VOLTAGE
MAX9928 toc06
OFFSET VOLTAGE vs. TEMPERATURE
-10
-20
-30
-40
-50
-60
-70
-80
0
-50
-25
0
25
50
75
TEMPERATURE (°C)
100
125
-2 -0.10
2
4
6
8
10
28
COMMON-MODE VOLTAGE (V)
_______________________________________________________________________________________
5
MAX9928/MAX9929
Typical Operating Characteristics
(VCC = 3.3V, VRS+ = 12V, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VCC = 3.3V, VRS+ = 12V, TA = +25°C, unless otherwise noted.)
TA = -40°C
6
2000
3.4
MAX9928 toc10
VOUT = 0V
MAX9928 toc09
2500
MAX9929F
VOUT vs. VSENSE
MAX9929F
VOUT vs. VSENSE
5
TA = -40°C
3.2
3.0
TA = +125°C
VOUT (V)
1500
VOUT (V)
3
VCC = 3.3V
1000
2
VCC = 2.7V
TA = +25°C
2.8
TA = +125°C
2.6
2.4
VCC = 2.5V
500
1
0
2.2
2.0
0
0.1
0.2
0.3
0.4
0.5
0
20
40
60
80
100
120
VSENSE (V)
VSENSE (mV)
GAIN ACCURACY
vs. SUPPLY VOLTAGE
MINIMUM OUTPUT VOLTAGE
vs. TEMPERATURE
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
5.0
4.5
4.0
3.0
2.5
2.0
1.5
1.0
0.2
0
-0.2
-0.4
-0.6
-0.8
-1.0
4.5
5.0
5.5
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
SMALL-SIGNAL GAIN
vs. FREQUENCY
MAX992_F
MAX9928 toc16
VCM = 3.6V
90
CMRR (dB)
32
GAIN (dB)
CMRR vs. FREQUENCY
120
MAX9928 toc15
35
29
26
60
30
23
20
0.01
0
0.1
1
10
FREQUENCY (kHz)
6
100
1000
90
0.4
0
4.0
80
0.6
-1.0
3.5
70
0.8
3.5
SUPPLY VOLTAGE (V)
60
GAIN ACCURACY vs. TEMPERATURE
0.5
3.0
50
1.0
-0.8
2.5
40
VSENSE (mV)
GAIN ACCURACY (%)
0.8
30
140
MAX9928 toc13
MAX9928 toc12
1.0
MINIMUM OUTPUT VOLTAGE (mV)
0
MAX9928 toc14
IOUT (μA)
VCC = 5.5V
4
TA = +25°C
MAX9928 toc11
MAX9928F
IOUT vs. VSENSE
GAIN ACCURANCY (%)
MAX9928/MAX9929
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
10
100
1k
10k
FREQUENCY (Hz)
_______________________________________________________________________________________
100k
1M
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
MAX9929F LARGE-SIGNAL
TRANSIENT RESPONSE
PSRR vs. FREQUENCY
0
VSENSE
-20
PSRR (dB)
MAX9928 toc18
MAX9928 toc17
20
50mV/div
-40
-60
-80
VOUT
1V/div
-100
-120
0.1
1
10
100
1k
10k
100k
100μs/div
FREQUENCY (Hz)
VSIGN AND VOUT
vs. VSENSE
OVERDRIVE RECOVERY
MAX9928 toc20
MAX9928 toc19
VSIGN (V)
4
3
2
VSENSE
100mV/div
1
VOUT (mV)
0
150
VOUT
500mV/div
100
50
0
-3
-2
-1
0
1
2
3
400μs/div
VSENSE (mV)
COMPARATOR PROPAGATION DELAY
(RS+ = 3.6V, 5mV OVERDRIVE)
POWER-UP DELAY
MAX9928 toc22
MAX9928 toc21
VCC
1V/div
VSENSE
2mV/div
VOUT
1V/div
VOUT
1V/div
40μs/div
40μs/div
_______________________________________________________________________________________
7
MAX9928/MAX9929
Typical Operating Characteristics (continued)
(VCC = 3.3V, VRS+ = 12V, TA = +25°C, unless otherwise noted.)
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
MAX9928/MAX9929
Pin/Bump Description
PIN
BUMP
µMAX
UCSP
1
B3
RS-
2
B2
SIGN
NAME
FUNCTION
Negative Current-Sense Input. Load-side connection for the external sense resistor.
SIGN Output. Indicates polarity of VSENSE.
SIGN = H indicates VRS+ > VRSSIGN = L indicates VRS+ < VRS-
3
B1
RS+
Positive Current-Sense Input. Power-side connection to the external sense resistor.
4, 5
—
N.C.
No Connection. Not internally connected.
6
A1
VCC
Supply Voltage Input. Bypass to GND with a 0.1µF capacitor.
7
A2
GND
Circuit Ground
8
A3
OUT
Current-Sense Output. MAX9928: Current output (IOUT is proportional to |VSENSE|). MAX9929:
Voltage output (VOUT is proportional to |VSENSE|).
Detailed Description
The MAX9928F/MAX9929F micropower uni-/bidirectional,
current-sense amplifiers feature -0.1V to +28V input
common-mode range that is independent of the supply
voltage. This wide input voltage range feature allows the
monitoring of the current flow out of a power supply during short-circuit/fault conditions, and also enables highside current sensing at voltages far in excess of the
supply voltage (VCC). The MAX9928F/MAX9929F operate from a 2.5V to 5.5V single supply and draw a low
20µA quiescent supply current.
Current flows through the sense resistor, generating a
sense voltage VSENSE (Figure 1). The comparator senses the direction of the sense voltage and configures the
amplifier for either positive or negative sense voltages
by controlling the S1 and S2 switches.
For positive VSENSE voltage, the amplifier’s inverting
input is high impedance and equals VIN - VSENSE. The
amplifier’s output drives the base of Q1, forcing its noninverting input terminal to (VIN - VSENSE); this causes a
current to flow through R G1 equal to |V SENSE |/R G1 .
Transistor Q2 and the current mirror amplify the current
by a factor of M.
For negative VSENSE voltage, the amplifier’s noninverting input is high impedance and the voltage on RS- terminal equals V IN + V SENSE. The amplifier’s output
drives the base of Q1 forcing its inverting input terminal
to match the voltage at the noninverting input terminal;
this causes a current to flow through R G2 equal to
|VSENSE|/RG2. Again, transistor Q2 and the current mirror amplify the current by a factor of M.
8
+VSENSE vs. -VSENSE
The amplifier is configured for either positive VSENSE or
negative VSENSE by the SIGN comparator. The comparator has a built-in offset skew of -1.2mV so that random offsets in the comparator do not affect the
precision of I OUT (V OUT) with positive V SENSE. The
comparator has a small amount of hysteresis (typically
0.6mV) to prevent its output from oscillating at the
crossover sense voltage. The ideal transfer characteristic of IOUT (VOUT) and the output of the comparator
(SIGN) is shown in Figure 2.
The amplifier VOS is only trimmed for the positive VSENSE
voltages (VRS+ > VRS-). The SIGN comparator reconfigures the internal structure of the amplifier to work with
negative VSENSE voltages (VRS- > VRS+) and the precision VOS trim is no longer effective and the resulting VOS
is slightly impacted. See details in the Electrical
Characteristics Note 2. The user can choose the direction that needs the best precision to be the direction
where VRS+ > VRS-. For example, when monitoring Li+
battery currents, the discharge current should be VRS+ >
VRS- to give the best accuracy over the largest dynamic
range. When the battery charger is plugged in, the
charge current flows in the opposite direction and is
usually much larger, and a higher VOS error can be
tolerated. See the Typical Operating Circuit.
For applications with unidirectional currents (e.g., battery discharge only), the SIGN output can be ignored.
Note that as VSENSE increases, the output current (IOUT
for the MAX9928 or VOUT/10kΩ for the MAX9929) also
increases. This additional current is supplied from VCC.
_______________________________________________________________________________________
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
MAX9928/MAX9929
VCC
2.5V TO 5.5V
VCC
RC1
80kΩ
MAX9928F
MAX9929F
RC2
80kΩ
1MΩ
SIGN
C
TO μC
CURRENT
MIRROR
VIN
-0.1V TO +28V
(VBATT)
RS+
VSENSE
RSENSE
+
S2
RG1
80kΩ
RG2
80kΩ
RS-
A
S1
OUT
Q2
TO ADC
10kΩ*
Q1
TO
LOAD/CHARGER
GND
*INTERNAL 10kΩ RESISTOR FOR MAX9929_ ONLY.
Figure 1. Functional Diagram
For both positive and negative VSENSE voltages, the
current flowing out of the current mirror is equal to:
IOUT = M x |VSENSE|/RG1
SIGN
For the MAX9928F, the transconductance of the device
is trimmed so that IOUT/|VSENSE| = 5µA/mV. For the
MAX9929F, the voltage gain of the device is trimmed
so that VOUT/|VSENSE| = 50V/V. The SIGN output from
the comparator indicates the polarity of VSENSE.
-1.8
-1.2
0
VSENSE (mV)
-3.0
-1.8
-1.2
0
VSENSE (mV)
1.0
2.0
3.0
1.0
2.0
3.0
IOUT (VOUT)
-3.0
( ) FOR THE MAX9929F.
Figure 2. Ideal Transfer Characteristics with 0mV Amplifier Input
Offset Voltage and -1mV Comparator Input Offset Voltage
Current Output (MAX9928F)
The output voltage equation for the MAX9928_ is given
below:
VOUT = (RSENSE x ILOAD) x (Gm X ROUT)
where VOUT = the desired full-scale output voltage,
ILOAD = the full-scale current being sensed, RSENSE =
the current-sense resistor, ROUT = the voltage-setting
resistor, and G m = MAX9928F transconductance
(5µA/mV).
The full-scale output voltage range can be set by
changing the ROUT resistor value. The above equation
can be modified to determine the ROUT required for a
particular full-scale range:
ROUT = (VOUT)/(ILOAD x RSENSE x Gm)
OUT is a high-impedance current source and can drive
an unlimited amount of capacitance.
_______________________________________________________________________________________
9
MAX9928/MAX9929
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
Voltage Output (MAX9929F)
The output voltage equation for the MAX9929_ is given
below:
VOUT = (RSENSE x ILOAD) x (AV)
where VOUT = the desired full-scale output voltage,
ILOAD = the full-scale current being sensed, RSENSE =
the current-sense resistor, A V = MAX9929F voltage
gain (50V/V).
SIGN Output
The current/voltage at OUT indicates magnitude. The
SIGN output indicates the current’s direction. The SIGN
comparator compares RS+ to RS-. The sign output is
high when RS+ is greater than RS- indicating positive
current flow. The sign output is low when RS- is greater
than RS+ indicating negative current flow. In batteryoperated systems, this is useful for determining
whether the battery is charging or discharging. The
SIGN output might not correctly indicate the direction of
load current when VSENSE is between -1.8mV to -1.2mV
(see Figure 2). Comparator hysteresis of 0.6mV prevents oscillation of SIGN output. If current direction is
not needed, leave SIGN unconnected.
Applications Information
Choosing RSENSE
The MAX9928F/MAX9929F operate over a wide variety
of current ranges with different sense resistors. Adjust
the RSENSE value to monitor higher or lower current levels. Select RSENSE using these guidelines:
• Voltage Loss: A high R SENSE value causes the
power-source voltage to drop due to IR loss. For
least voltage loss, use the lowest RSENSE value.
• Accuracy: A high RSENSE value allows lower currents to be measured more accurately. This is
because offsets become less significant when the
sense voltage is larger.
tor value and power dissipation (wattage) rating.
Also, if the sense resistor is allowed to heat up excessively, its value could drift.
• Inductance: If there is a large high-frequency component to ISENSE, keep inductance low. Wire-wound
resistors have the highest inductance, while metal
film is somewhat better. Low-inductance metal-film
resistors are available. Instead of being spiral
wrapped around a core, as in metal film or wirewound resistors, these are a straight band of metal.
They are made in values under 1Ω.
Use in Systems with Super Capacitors
Since the input common-mode voltage range of the
MAX9928/MAX9929 extends all the way from -0.1V to
28V, they are ideal to use in applications that require
use of super capacitors for temporary or emergency
energy storage systems. Some modern industrial and
automotive systems use multifarad (1F–50F) capacitor
banks to supply enough energy to keep critical systems alive even if the primary power source is removed
or temporarily disabled. Unlike batteries, these capacitors can discharge all the way down to 0V. The
MAX9928/MAX9929 can continuously help monitor their
health and state of charge/discharge.
UCSP Applications Information
For the latest application details on UCSP construction,
dimensions, tape carrier information, PCB techniques,
bump-pad layout, and recommended reflow temperature profile, as well as the latest information on reliability
testing results, go to Maxim’s website at www.maximic.com/ucsp to find Application Note 1891:
Understanding the Basics of the Wafer-Level ChipScale Package (WL-CSP).
Chip Information
PROCESS: BiCMOS
• Efficiency and Power Dissipation: At high current
levels, the I2R losses in RSENSE might be significant.
Take this into consideration when choosing the resis-
10
______________________________________________________________________________________
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
TOP VIEW
(BUMPS ON THE BOTTOM)
TOP VIEW
RS-
1
SIGN
2
RS+
3
N.C.
4
+
8
OUT
7
GND
6
VCC
5
N.C.
A
MAX9928F
MAX9929F
1
2
3
VCC
GND
OUT
MAX9928F
MAX9929F
μMAX
B
RS+
SIGN
RS-
UCSP
(1mm x 1.5mm)
Typical Operating Circuit
WALL-CUBE
CHARGER
RSENSE
VIN
-0.1V TO
+28V
RS+
2.5V TO
5.5V
LOAD
RS-
μC
MAX9928F
MAX9929F SIGN
VCC
DIGITAL
INPUT
0.1μF
ADC
OUT
GND
ROUT*
GND
*FOR THE MAX9928F ONLY
______________________________________________________________________________________
11
MAX9928/MAX9929
Pin Configurations
MAX9928/MAX9929
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
Package Information
For the latest package outline information and land patterns (footprints), 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
OUTLINE NO.
LAND PATTERN NO.
8 µMAX
U8+1
21-0036
90-0092
6 UCSP
B6+1
21-0097
—
α
α
12
______________________________________________________________________________________
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
______________________________________________________________________________________
13
MAX9928/MAX9929
Package Information (continued)
For the latest package outline information and land patterns (footprints), 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.
MAX9928/MAX9929
-0.1V to +28V Input Range, Micropower,
Uni-/Bidirectional, Current-Sense Amplifiers
Revision History
REVISION
NUMBER
REVISION
DATE
0
12/08
Initial release
1
8/09
Removed MAX9928T and MAX9929T from data sheet
2
4/11
Updated top marks
DESCRIPTION
PAGES
CHANGED
—
1–5, 7–12
1
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.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2011 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.