MAX472CSA ,Precision, High-Side Current-Sense AmplifiersMAX471/MAX47219-0335; Rev 2; 12/96Precision, High-Side Current-Sense Amplifiers_______________
MAX472CSA+ ,Precision, High-Side Current-Sense AmplifiersFeaturesThe MAX471/MAX472 are complete, bidirectional, high-♦ Complete High-Side Current Sensingsid ..
MAX472ESA ,Precision, High-Side Current-Sense AmplifiersFeaturesThe MAX471/MAX472 are complete, bidirectional, high-' Complete High-Side Current Sensingsid ..
MAX472ESA-T ,Precision, High-Side Current-Sense AmplifiersApplicationsMAX471CSA 0°C to +70°C 8 SOPortable PCs:MAX471EPA -40°C to +85°C 8 Plastic DIPNotebooks ..
MAX4731EUA+ ,50 Ohm, Dual SPST Analog Switches in UCSPApplications RANGE PACKAGE MARKMAX4731EUA -40°C to +85°C 8 µMAX —Battery-Powered SystemsMAX4731ETA ..
MAX4731EUA+T ,50 Ohm, Dual SPST Analog Switches in UCSPapplications.♦ Guaranteed < 0.1nA Leakage Current at When powered from a +3V supply, these switches ..
MAX8868EUK50-T ,Low-noise, low-dropout, 150mA linear regulator with auto discharge function. Preset output voltage 5.00V
MAX8869EUE25+T ,1A, Microcap, Low-Dropout, Linear Regulator
MAX8869EUE50+ ,1A, Microcap, Low-Dropout, Linear Regulator
MAX8869EUE50+ ,1A, Microcap, Low-Dropout, Linear Regulator
MAX8873REUK+T ,Low-Dropout 120mA Linear Regulators
MAX8873REUK-T ,Low-Dropout, 120mA Linear Regulators
MAX471CPA-MAX471CSA-MAX471ESA-MAX472CSA-MAX472ESA
Precision, High-Side Current-Sense Amplifiers
_______________General DescriptionThe MAX471/MAX472 are complete, bidirectional, high-
side current-sense amplifiers for portable PCs, tele-
phones, and other systems where battery/DC
power-line monitoring is critical. High-side power-line
monitoring is especially useful in battery-powered sys-
tems, since it does not interfere with the ground paths
of the battery chargers or monitors often found in
“smart” batteries.
The MAX471 has an internal 35mΩcurrent-sense resis-
tor and measures battery currents up to ±3A. For appli-
cations requiring higher current or increased flexibility,
the MAX472 functions with external sense and gain-set-
ting resistors. Both devices have a current output that
can be converted to a ground-referred voltage with a
single resistor, allowing a wide range of battery volt-
ages and currents.
An open-collector SIGN output indicates current-flow
direction, so the user can monitor whether a battery is
being charged or discharged. Both devices operate
from 3V to 36V, draw less than 100µA over tempera-
ture, and include a 18µA max shutdown mode.
________________________ApplicationsPortable PCs:
Notebooks/Subnotebooks/Palmtops
Smart Battery Packs
Cellular Phones
Portable Phones
Portable Test/Measurement Systems
Battery-Operated Systems
Energy Management Systems
____________________________FeaturesComplete High-Side Current SensingPrecision Internal Sense Resistor (MAX471)2% Accuracy Over TemperatureMonitors Both Charge and Discharge3A Sense Capability with Internal Sense Resistor
(MAX471)Higher Current-Sense Capability with External
Sense Resistor (MAX472)100µA Max Supply Current18µA Max Shutdown Mode3V to 36V Supply Operation8-Pin DIP/SO Packages
______________Ordering Information
MAX471/MAX472
Precision, High-Side
Current-Sense Amplifiers
_________________Pin Configurations
__________Typical Operating Circuit19-0335; Rev 2; 12/96
MAX471/MAX472
Precision, High-Side
Current-Sense Amplifiers
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS—MAX471(RS+ = +3V to +36V, TA= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°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.
Supply Voltage, RS+, RS-, VCCto GND....................-0.3V, +40V
RMS Current, RS+ to RS- (MAX471 only)..........................±3.3A
Peak Current, (RS+ to RS-)......................................see Figure 5
Differential Input Voltage, RG1 to RG2 (MAX472 only) .....±0.3V
Voltage at Any Pin Except SIGN
MAX471 only...........................................-0.3V to (RS+ - 0.3V)
MAX472 only..........................................-0.3V to (VCC+ 0.3V)
Voltage at SIGN......................................................-0.3V to +40V
Current into SHDN, GND, OUT, RG1, RG2, VCC................±50mA
Current into SIGN.................................................+10mA, -50mA
Continuous Power Dissipation (TA= +70°C)
MAX471 (Note 1):
Plastic DIP (derate 17.5mW/°C above +70°C)..................1.4W
SO (derate 9.9mW/°C above +70°C).............................791mW
MAX472 :
Plastic DIP (derate 9.09mW/°C above +70°C)..............727mW
SO (derate 5.88mW/°C above +70°C)...........................471mW
Operating Temperature Ranges
MAX47_C_A........................................................0°C to +70°C
MAX47_E_A.....................................................-40°C to +85°C
Junction Temperature Range............................-60°C to +150°C
Storage Temperature Range.............................-60°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
Note 1:Due to special packaging considerations, MAX471 (DIP, SO) has a higher power dissipation rating than the MAX472. RS+
andRS- must be soldered to large copper traces to achieve this dissipation rating.
MAX471/MAX472
Precision, High-Side
Current-Sense Amplifiers
ELECTRICAL CHARACTERISTICS—MAX472(VCC= +3V to +36V, RG1 = RG2 = 200Ω, TA= TMINto TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
Note 2:VOSis defined as the input voltage (VSENSE) required to give minimum IOUT.
Note 3:VSENSEis the voltage across the sense resistor.
MAX471/MAX472
Precision, High-Side
Current-Sense Amplifiers
__________________________________________Typical Operating Characteristics(Typical Operating Circuit (MAX471) or circuit of Figure 4, RG1 = RG2 = 200Ω, ROUT= 2kΩ(MAX472), TA= +25°C, unless
otherwise noted.)
SUPPLY CURRENT vs.
SUPPLY VOLTAGEMAX1471-01
VRS+ (V)
SUPPLY CURRENT (2415189123627303336
MAX1471-02
SHDN1.5
SHUTDOWN CURRENT vs.
SUPPLY VOLTAGE
VRS+(V)2415189123627303336
SIGN THRESHOLD vs.
SUPPLY VOLTAGEMAX1471-03
SIGN THRESHOLD (mA)2415189123627303336
VRS+ (V)
MAX1471-04
OFFSET CURRENT (
MAX471
NO-LOAD OFFSET CURRENT vs.
SUPPLY VOLTAGEVRS+ (V)2415189123627303336
TEMPERATURE (°C)
RESISTANCE (m
MAX1471-07
MAX471
RS+ TO RS- RESISTANCE vs.
TEMPERATUREMAX471
ERROR vs. LOAD CURRENT
MAX471-05
ILOAD (A)
ERROR (%)
MAX471
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX471-06
POWER-SUPPLY FREQUENCY (kHz)
PSRR (%)100
MAX472
NO-LOAD OUTPUT ERROR vs.
SUPPLY VOLTAGE
MAX1471-08
VCC (V)
IOUT2415189123627303336
MAX1471-09
ERROR (%)
MAX472
ERROR vs. SUPPLY VOLTAGEVCC (V)2415189123627303336
1.10
MAX471/MAX472
Precision, High-Side
Current-Sense AmplifiersMAX472
ERROR vs. SENSE VOLTAGE
MAX471-10
VSENSE (mV)
ERROR (%)
-15100
1mA10mA100mA1A
MAX471
NOISE vs. LOAD CURRENT
ISENSE
IOUT
NOISE (µA
RMS
MAX471-15
____________________________Typical Operating Characteristics (continued)(Typical Operating Circuit (MAX471) or circuit of Figure 4, RG1 = RG2 = 200Ω, ROUT= 2kΩ(MAX472), TA= +25°C, unless
otherwise noted.)
MAX471/MAX472
_______________Detailed DescriptionThe MAX471 and MAX472 current-sense amplifier’s
unique topology allows a simple design to accurately
monitor current flow. The MAX471/MAX472 contain two
amplifiers operating as shown in Figures 1 and 2. The
battery/load current flows from RS+ to RS- (or vice
versa) through RSENSE. Current flows through either
RG1 and Q1 or RG2 and Q2, depending on the sense-
resistor current direction. Internal circuitry, not shown in
Figures 1 and 2, prevents Q1 and Q2 from turning on at
the same time. The MAX472 is identical to the
MAX471, except that RSENSEand gain-setting resistors
RG1 and RG2 are external (Figure 2).
To analyze the circuit of Figure 1, assume that current
flows from RS+ to RS- and that OUT is connected to
GND through a resistor. In this case, amplifier A1 is
active and output current IOUTflows from the emitter of
Q1. Since no current flows through RG2 (Q2 is off), the
negative input of A1 is equal to VSOURCE- (ILOADx
RSENSE). The open-loop gain of A1 forces its positive
input to essentially the same level as the negative input.
Therefore, the drop across RG1 equals ILOADx
RSENSE. Then, since IOUTflows through Q1 and RG
(ignoring the extremely low base currents), IOUTx RG1
= ILOADx RSENSE, or:
IOUT= (ILOADx RSENSE)/ RG1
Current OutputThe output voltage equation for the MAX471/MAX472 is
given below. In the MAX471, the current-gain ratio has
been preset to 500µA/A so that an output resistor
(ROUT) of 2kΩyields 1V/A for a full-scale value of +3V
at ±3A. Other full-scale voltages can be set with differ-
ent ROUTvalues, but the output voltage can be no
greater than VRS+- 1.5V for the MAX471 or VRG_- 1.5V
for the MAX472.
VOUT= (RSENSEx ROUTx ILOAD) / RG
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 RG = the gain-setting resistor (RG = RG1
= RG2).
The above equation can be modified to determine the
ROUTrequired for a particular full-scale range:
ROUT= (VOUTx RG) / (ILOADx RSENSE)
For the MAX471, this reduces to:
ROUT= VOUT/ (ILOADx 500µA/A)
OUT is a high-impedance current-source output that
can be connected to other MAX471/MAX472 OUT pins
Precision, High-Side
Current-Sense Amplifiers
______________________________________________________________Pin Description
