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acquisitionZONE Products for the week of January 14, 2008
Maxim Integrated Products Says…
MAX4208/09H: Spread-Spectrum, Autozero Instrumentation Amplifiers with Patented Architecture
Guarantee <20µV Offset Voltage and Eliminate Drift over Time and Temperature
Maxim Integrated Products introduced the MAX4208/MAX4209H instrumentation amplifiers that feature the Company's patented current-feedback architecture, a spread-spectrum autozeroing technique. The new autozeroing technology constantly measures and corrects the input offset voltage, thereby eliminating drift over time and temperature. The input offset voltage is 20µV (max) at +25°C, and 40µV (max) over the 40°C to +125°C temperature range. The technology's compact design allows the MAX4208/MAX4209H to fit in a small, 3mm x 5mm µMAX package, making them ideal for use in a wide range of applications. The amplifiers can monitor the low-voltage, power-supply currents of the core, ASIC and microprocessor in laptop computers. The amplifiers are also used in automotive, industrial, and medical instrumentation.
EN-Genius Says…
The MAX4208 and MAX4209 are instrumentation amplifiers with a differential transconductance input stage producing a current. Instead of the conventional three-op amp architecture a portion of the output stage voltage (equal to the input) is also converted to a current. These two currents are subtracted and fed to a loop amplifier.
A reference voltage (usually Vdd/2) level shifts the output so that bipolar signals can be handled. The input offset is minimized with a patented spread-spectrum autozeroing technique. Typical numbers are ±3 µV for input offset voltage and 1 pA for input offset current. The input bias current is also a typical 1 pA.
With true ground sensing the input common-mode voltage range is -0.1 V to Vdd – 1.3 V. The maximum recommended differential input voltage range is ±100 mV with both linearity and accuracy suffering at higher levels. Both differential and common-mode input resistance are 2 GΩ and input noise voltage is a typical 2.4 µVpp from 0.1 Hz to 10 Hz. The input noise has a white characteristic. The outputs go within a typical 30 mV (low and high) of the rail with a 100 kΩ load, and within 250 mV (low and high) with a 1 kΩ load.
Gain-bandwidth product is a typical 750 kHz at unity gain with the small-signal bandwidth falling directly in ratio to gain. Slew rate is a typical 80 V/ms at unity gain and 55 V/ms at a gain of 10V/V. Gain error is a typical 0.05% up to 100 V/V and 0.10% at 1000 V/V. Gain non-linearity (within the advised limits of the input voltage) is a typical 25 ppm up to 100 V/V and 50 ppm at 1000 V/V. CMRR is guaranteed to be better than 106 dB with PSRR better than 100 dB.
The difference between the two parts is that the feedback resistors, to set gain, are laser-trimmed and internal on the MAX4209 and fixed gain versions are offered at 10 V/V, 100 V/V, and 1000 V/V. On the MAX4208 the gain is set by the customer using two external resistors.
The rail voltage can be between 2.85 V and 5.5 V. The data sheet is characterized at 5 V when the highest quiescent is 2.3 mA and the shutdown current is 5.0 µA. The data sheet offers, very correctly for a precision part, the specifications at +25ºC and over the automotive temperature range of -40ºC to +125ºC,
This is a fairly remarkable part which must be considered for a whole slew of sensing applications, particularly bridge inputs. Maxim does not have a reputation for precision parts and I, for one, will be watching to see that what is delivered is what is promised. Doing “precision analog” is, generally, a complete program and not just one part. If Maxim delivers they will come to realize that the part is grievously under priced. The architecture is, however, masterful.
The MAX4208 and MAX4209H are sampling now in µMAX-8. They will be priced at $1.65 in 1000-piece lots.
Data Sheet
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