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19-4251; Rev 2; 4/11
KIT ATION EVALU ILABLE AVA
-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers
General Description
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 20A 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 5A/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 10k 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 -40C to +125C automotive temperature range, and available in 6-bump UCSPTM (1mm x 1.5mm) and 8-pin MAX(R) packages. The UCSP package is bump-to-bump compatible with the MAX4372_EBT.
UCSP is a trademark and MAX is a registered trademark of Maxim Integrated Products, Inc. Pin Configurations and Typical Operating Circuit appear at end of data sheet.
Features
o Wide -0.1V to +28V Common-Mode Range, Independent of Supply Voltage o 2.5V to 5.5V Operating Supply Voltage o 20A 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 5A/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 MAX Packages
MAX9928/MAX9929
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 Smart Cell Phones Super Capacitor Charge/Discharge
Ordering Information
PART MAX9928FAUA+ MAX9928FABT+T * MAX9929FAUA+ MAX9929FABT+T * OUTPUT TYPE Current Current Voltage Voltage GAIN Gm = 5A/mV Gm = 5A/mV AV = 50V/V AV = 50V/V PIN-PACKAGE 8 MAX 3x2 UCSP 8 MAX 3x2 UCSP TOP MARK -- +AAF -- +ADI
Note: All devices are specified over the -40C to +125C 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
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.
-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers MAX9928/MAX9929
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 = +70C) 6-Bump 1mm x 1.5mm UCSP (derate 3.9mW/C above +70C) ............................308.3mW 8-Pin MAX (derate 4.8mW/C above +70C) .............388mW Operating Temperature Range ........................-40C to +125C Storage Temperature Range ............................-65C to +150C Junction Temperature .....................................................+150C Lead Temperature (soldering, 10s) .................................+300C Soldering Temperature (reflow) .......................................+260C
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 = 10k for MAX9928F, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER SYMBOL CONDITIONS TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C -0.1 TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C 93 87 60 54 50 50 TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C 0 -80 0.05 0.2 0.05 1.6 5 0.3 0.3 0.3 0.3 1.0 2.5 1.0 2.8 A/mV 1.0 2.5 1.0 2.8 6 +6 1 2 1.0 A A A % mV V/V 72 104 dB 0.6 MIN TYP 0.1 MAX 0.4 0.8 1.0 3.0 +28 V mV UNITS AMPLIFIER DC ELECTRICAL CHARACTERISTICS VRS+ = 3.6V Input Offset Voltage (Note 2) VOS VRS+ = -0.1V Common-Mode Input Range VCMR (Note 3) 2V VRS+ 28V Common-Mode Rejection Ratio CMRR -0.1V VRS+ +2V MAX992_F MAX9929F MAX9929F, VRS+ = 3.6V MAX9929F, VRS+ = -0.1V Transconductance (Note 2) Transconductance Accuracy (Note 2) GM MAX9928F MAX9928F, VRS+ = 3.6V MAX9928F, VRS+ = -0.1V IRS+, IRSIOS IRS+, IRS2V VRS+ 28V -0.1V VRS+ +2V 2V VRS+ 28V -0.1V VRS+ +2V VCC = 0V, VRS+ = VRS- = 28V (Note 5)
Full-Scale Sense Voltage (Note 2) Gain (Note 2)
VSENSE AV
Gain Accuracy (Notes 2, 6)
%
Input Bias Current (Note 4) Input Offset Bias Current (Note 4) Input Leakage Current
2
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-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 = 10k for MAX9928F, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Output Resistance SYMBOL ROUT MAX9928F MAX9929F MAX9928F, ROUT = 10k Output High Voltage (Note 6) VOH MAX9929F Minimum Output Voltage (Note 7) Minimum Output Current (Note 7) VOL IOL MAX9929F MAX9928F TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C TA = +25C TA = -40C to +125C TA = +25C TA = +25C TA = +25C -0.1 2V VRS+ 28V -0.1V VRS+ +2V ISINK = 100A 102 74 0.03 (VCC 0.01) 1 TA = +25C TA = -40C to +125C VRS+ = 3.6V VRS+ = -0.1V VRS+ = 3.6V VRS+ = -0.1V 2V VRS+ 28V -0.1V VRS+ < +2V 2.5 2.8 72 66 90 86 90 86 20 115 30 200 5.5 5.5 0.1 (VCC 0.04) -1.6 -2.15 -2.5 -4.6 -1.8 -1.8 0.6 +28 -1.2 -1.2 6.4 CONDITIONS MIN TYP 5 10 (VCC 0.1) (VCC 0.1) 0.25 0.025 13.6 (VCC 0.45) V (VCC 0.45) 2.0 15 0.2 1.5 -0.5 -0.15 +0.25 +2.3 mV mV V dB V V M mV A MAX UNITS M k
MAX9928/MAX9929
SIGN COMPARATOR DC ELECTRICAL CHARACTERISTICS Discharge to Charge Trip Point (Note 8) Charge to Discharge Trip Point (Note 8) Hysteresis Width Common-Mode Input Range (Note 9) Common-Mode Rejection Ratio (Note 9) Output Low Voltage Output High Voltage Internal Pullup Resistor POWER SUPPLY Supply Voltage Range (Note 10) Amplifier Power-Supply Rejection Ratio (Note 10) Comparator Power-Supply Rejection Ratio Quiescent Supply Current VCC PSRRA PSRRC ICC V dB dB A VRS+ = 3.6V VTDC VRS+ = -0.1V VTCD VHYS VCMR CMRR VOL VOH RPULL-UP VRS+ = 3.6V VRS+ = -0.1V VRS+ = 3.6V, -0.1V
mV
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-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers MAX9928/MAX9929
ELECTRICAL CHARACTERISTICS (continued)
(VRS+ = -0.1V to +28V, VCC = 3.3V, VSENSE = (VRS+ - VRS-) = 0V, ROUT = 10k for MAX9928F, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER -3dB Bandwidth SYMBOL BW CONDITIONS MAX992_F, VSENSE = 50mV VRS+ = 3.6V, CLOAD = 10pF, ROUT = 10k for MAX992_F, VSENSE = MAX9928F 50mV to 5mV step Overdrive = 1mV Overdrive = 5mV Overdrive = 1mV Overdrive = 5mV VSENSE = 50mV for MAX992_F, VRS+ = 3.6V, CLOAD = 10pF 100mV VSENSE 50mV for MAX992_F, VRS+ = 3.6V, CLOAD = 10pF MAX992_F, VSENSE = 5mV to 50mV step MIN TYP 150 6 s 15 80 30 50 13 50 4 s s s ms MAX UNITS kHz
AC ELECTRICAL CHARACTERISTICS
OUT Settling to 1% of Final Value
tSET
SIGN Comparator Propagation Delay (Low to High) SIGN Comparator Propagation Delay (High to Low) Power-Up Time to 1% of Final Value Saturation Recovery Time
tPROP_LH tPROP_HL
Note 1: All devices are 100% production tested at TA = +25C. 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 +25C 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.
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-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers
Typical Operating Characteristics
(VCC = 3.3V, VRS+ = 12V, TA = +25C, unless otherwise noted.)
GAIN ACCURACY HISTOGRAM
MAX9928 toc01
MAX9928/MAX9929
VOS HISTOGRAM
45 40 35 FREQUENCY (%) 30 25 20 15 10 5 0 -0.40 -0.30 -0.20 -0.10 0 0.10 0.20 0.30 0.40 5 0 AV = 50V/V 30 AV = 50V/V 25 FREQUENCY (%) 20 15 10
OFFSET VOLTAGE vs. COMMON-MODE VOLTAGE
MAX9928 toc02
1.5 OFFSET VOLTAGE (mV) 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0 -1 0 1 2 3 28
-1.0 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 GAIN ACCURACY (%)
COMMON-MODE VOLTAGE (V)
VOS (mV)
OFFSET VOLTAGE vs. TEMPERATURE
MAX9928 toc04
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9928 toc05
SUPPLY CURRENT vs. COMMON-MODE VOLTAGE
MAX9928 toc06
1.0 0.8 0.6 OFFSET VOLTAGE (mV) 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 VCM = 3.6V
150 VSENSE = 0V 125 SUPPLY CURRENT (A) 100 75 50 VRS+ = 3.6V 25 0 2.5 3.0 3.5 4.0 4.5 5.0 VRS+ = 0V
150
120 SUPPLY CURRENT (A)
90
VCC = 5.5V
60 VCC = 2.5V 30
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
0 5.5 -0.5 0 0.5 1.0 1.5 2.0 28 SUPPLY VOLTAGE (V) COMMON-MODE VOLTAGE (V)
SUPPLY CURRENT vs. TEMPERATURE
VSENSE = 0V 125 SUPPLY CURRENT (A) 100 75 50 VRS+ = 3.6V 25 0 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) VRS+ = 0V
MAX9928 toc07
INPUT BIAS CURRENT vs. COMMON-MODE VOLTAGE
0 INPUT BIAS CURRENT (A) -10 -20 -30 -40 -50 -60 -70 -80 -2 -0.10 2 4 6 8 10 28
MAX9928 toc08
150
10
COMMON-MODE VOLTAGE (V)
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MAX9928 toc03
2.0
5
-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers MAX9928/MAX9929
Typical Operating Characteristics (continued)
(VCC = 3.3V, VRS+ = 12V, TA = +25C, unless otherwise noted.)
MAX9928F IOUT vs. VSENSE
MAX9928 toc09
MAX9929F VOUT vs. VSENSE
MAX9928 toc10
MAX9929F VOUT vs. VSENSE
TA = -40C 3.2 3.0 VOUT (V) 2.8 2.6 2.4 2.2 2.0 TA = +125C TA = +25C
MAX9928 toc11
2500
VOUT = 0V
6 5 VCC = 5.5V 4 VOUT (V) 3 VCC = 3.3V 2 VCC = 2.7V VCC = 2.5V 1 0
3.4
TA = -40C
2000 TA = +25C TA = +125C 1000
IOUT (A)
1500
500
0 0 0.1 0.2 0.3 0.4 0.5 VSENSE (V)
0
20
40
60
80
100
120
140
30
40
50
60 VSENSE (mV)
70
80
90
VSENSE (mV)
GAIN ACCURACY vs. SUPPLY VOLTAGE
MAX9928 toc12
MINIMUM OUTPUT VOLTAGE vs. TEMPERATURE
MAX9928 toc13
GAIN ACCURACY vs. TEMPERATURE
0.8 0.6 GAIN ACCURACY (%) 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0
MAX9928 toc14
1.0 0.8 0.6 GAIN ACCURANCY (%) 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 2.5 3.0 3.5 4.0 4.5 5.0
5.0 4.5 MINIMUM OUTPUT VOLTAGE (mV) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0
1.0
5.5
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
SUPPLY VOLTAGE (V)
SMALL-SIGNAL GAIN vs. FREQUENCY
VCM = 3.6V MAX992_F
MAX9928 toc15
CMRR vs. FREQUENCY
MAX9928 toc16
35
120
32
90 CMRR (dB)
GAIN (dB)
29
60
26
30 23
20 0.01
0 0.1 1 10 100 1000 10 100 1k 10k 100k 1M FREQUENCY (kHz) FREQUENCY (Hz)
6
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-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers
Typical Operating Characteristics (continued)
(VCC = 3.3V, VRS+ = 12V, TA = +25C, unless otherwise noted.)
MAX9929F LARGE-SIGNAL TRANSIENT RESPONSE
MAX9928 toc17 MAX9928 toc18
MAX9928/MAX9929
PSRR vs. FREQUENCY
20 0 -20 PSRR (dB) -40 -60 -80 -100 -120 0.1 1 10 100 1k 10k 100k VOUT
VSENSE
50mV/div
1V/div
100s/div
FREQUENCY (Hz)
VSIGN AND VOUT vs. VSENSE
3 2 1 0 VOUT (mV) 150 100 50 0 -3 -2 -1 0 VSENSE (mV) 1 2 3
MAX9928 toc19
OVERDRIVE RECOVERY
MAX9928 toc20
4 VSIGN (V)
VSENSE 100mV/div
VOUT 500mV/div
400s/div
COMPARATOR PROPAGATION DELAY (RS+ = 3.6V, 5mV OVERDRIVE)
MAX9928 toc21
POWER-UP DELAY
MAX9928 toc22
VCC 1V/div VSENSE 2mV/div VOUT 1V/div VOUT 1V/div
40s/div
40s/div
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-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers MAX9928/MAX9929
Pin/Bump Description
PIN MAX 1 2 3 4, 5 6 7 8 BUMP UCSP B3 B2 B1 -- A1 A2 A3 NAME RSSIGN RS+ N.C. VCC GND OUT 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+ < VRSPositive Current-Sense Input. Power-side connection to the external sense resistor. No Connection. Not internally connected. Supply Voltage Input. Bypass to GND with a 0.1F capacitor. Circuit Ground 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 20A 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.
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+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/10k for the MAX9929) also increases. This additional current is supplied from VCC.
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-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers MAX9928/MAX9929
2.5V TO 5.5V VCC RC1 80k VCC
MAX9928F MAX9929F C
1M SIGN TO C
RC2 80k
CURRENT MIRROR VIN -0.1V TO +28V (VBATT) + RS+ S2
RG1 80k
OUT
TO ADC
RSENSE
VSENSE
RS-
RG2 80k
A
S1 Q1
Q2
10k*
TO LOAD/CHARGER *INTERNAL 10k RESISTOR FOR MAX9929_ ONLY. GND
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 For the MAX9928F, the transconductance of the device is trimmed so that IOUT/|VSENSE| = 5A/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.
1.0 2.0 3.0
SIGN
-3.0
-1.8
-1.2
0 VSENSE (mV)
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 (5A/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.
-3.0
-1.8
-1.2
0 VSENSE (mV)
IOUT (VOUT)
1.0
2.0
3.0
( ) FOR THE MAX9929F.
Figure 2. Ideal Transfer Characteristics with 0mV Amplifier Input Offset Voltage and -1mV Comparator Input Offset Voltage
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-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers MAX9928/MAX9929
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). 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 1.
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.
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.
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.
* Efficiency and Power Dissipation: At high current levels, the I2R losses in RSENSE might be significant. Take this into consideration when choosing the resis-
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
10
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-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers
Pin Configurations
TOP VIEW (BUMPS ON THE BOTTOM)
1 RSSIGN RS+ N.C. 1 2 3 4 + 8 7 OUT A GND VCC N.C. VCC 2 GND 3 OUT
MAX9928/MAX9929
TOP VIEW
MAX9928F MAX9929F
6 5
MAX9928F MAX9929F
B RS+ SIGN RS-
MAX
UCSP (1mm x 1.5mm)
Typical Operating Circuit
WALL-CUBE CHARGER VIN -0.1V TO +28V RS+ RSENSE LOAD C DIGITAL INPUT ADC ROUT* GND *FOR THE MAX9928F ONLY
RS-
2.5V TO 5.5V 0.1F
VCC
MAX9928F MAX9929F SIGN
OUT GND
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11
-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers MAX9928/MAX9929
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 8 MAX 6 UCSP PACKAGE CODE U8+1 B6+1 OUTLINE NO. 21-0036 21-0097 LAND PATTERN NO. 90-0092 --
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-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers
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
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-0.1V to +28V Input Range, Micropower, Uni-/Bidirectional, Current-Sense Amplifiers MAX9928/MAX9929
Revision History
REVISION NUMBER 0 1 2 REVISION DATE 12/08 8/09 4/11 Initial release Removed MAX9928T and MAX9929T from data sheet 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 (c) 2011 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

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