Datasheet MAX4073T, MAX4073F, MAX4073H (Maxim) - 7

MAX4073T/F/H Low-Cost, SC70, Voltage-Output, High-Side Current-Sense Amplifier Pin Description PIN NAME FUNCTION SOT23 SC70
1, 2 2 GND Ground 3 3 VCC Supply Voltage Input. Bypass to GND with a 0.1µF capacitor. 4 4 RS+ Power-Side Connection to the External Sense Resistor 5 5 RS- Load-Side Connection to the External Sense Resistor Voltage Output. V 6 1 OUT OUT is proportional to VSENSE. Output impedance is approximately 12kΩ.
Detailed Description
ILOAD R The MAX4073 high-side current-sense amplifier fea- SENSE TO LOAD/BATTERY VSOURCE tures a +2V to +28V input common-mode range that is +2V TO +28V independent of supply voltage. This feature allows the RS+ RS- monitoring of current out of a battery as low as +2V and IRG1 also enables high-side current sensing at voltages +3V TO +28V RG1 RG2 VCC greater than the supply voltage (VCC). The MAX4073 operates as follows: current from the source flows through RSENSE to the load (Figure 1). Since A1 the internal-sense amplifier’s inverting input has high impedance, negligible current flows through RG2 (neglecting the input bias current). Therefore, the sense amplifier’s inverting-input voltage equals MAX4073T/F/H VSOURCE - (ILOAD)(RSENSE). The amplifier’s open-loop gain forces its noninverting input to the same voltage as VOUT CURRENT OUT the inverting input. Therefore, the drop across RG1 MIRROR equals (ILOAD)(RSENSE). Since IRG1 flows through RG1, IRGD IRG1 = (ILOAD)(RSENSE) / RG1. The internal current mirror multiplies IRG1 by a current gain factor, β, to give RGD = 12kΩ IRGD = β ✕ IRG1. Solving IRGD = β ✕ (ILOAD)(RSENSE)/ GND RG1. Assuming infinite output impedance, VOUT = (IRGD) (RGD). Substituting in for IRGD and rearranging, VOUT = β ✕ (RGD/RG1)(RSENSE ✕ ILOAD). The parts gain equals β ✕ RGD/RG1. Therefore, VOUT = (GAIN) (RSENSE) Figure 1. Functional Diagram (ILOAD), where GAIN = 20V/V for MAX4073T, GAIN = 50V/V for MAX4073F, and GAIN = 100V/V for MAX4073H. higher-sense voltage that reduces offset voltage errors Set the full-scale output range by selecting RSENSE and of the internal op amp. Typical sense voltages range the appropriate gain version of the MAX4073. between 10mV and 150mV.
Applications Information
In applications monitoring very high currents, RSENSE must be able to dissipate the I2R losses. If the resistor’s
Recommended Component Values
rated power dissipation is exceeded, its value may drift The MAX4073 senses a wide variety of currents with or it may fail altogether, causing a differential voltage different sense resistor values. Table 1 lists common across the terminals in excess of the absolute maxi- resistor values for typical operation of the MAX4073. mum ratings (±5V).
Choosing R
If I
SENSE
SENSE has a large high-frequency component, mini- To measure lower currents more accurately, use a mize the inductance of RSENSE. Wire-wound resistors large value for R have the highest inductance, metal-film resistors are SENSE. The larger value develops a
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Maxim Integrated