Instrumentation Amplifiers come in 3 x 5 mm MAX package.
Press Release Summary:
Using spread-spectrum autozeroing technique, Models MAX4208/MAX4209H instrumentation amplifiers achieve maximum VOS of 20, 30, and 40 µV at +25, +85, and +125°C, respectively. Indirect current-feedback architecture offers true ground sensing and input common-mode voltage range of -0.1 to 1.3 V. With CMRR of 106 dB (min), units feature 2-transconductance-amplifier architecture, CMOS transistors with 1 pA (typ) input bias current, and 40-125°C temperature range.
Original Press Release:
Spread-Spectrum, Autozero Instrumentation Amplifiers with Patented Architecture Guarantee < 20µV Offset Voltage and Eliminates Drift over Time and Temperature
Offset Voltage and Eliminates Drift over Time and Temperature
o The MAX4208/MAX4209H instrumentation amplifiers use a patented spread-spectrum, autozero technique to achieve VOS of 20µV (max) at +25°C, 30µV (max) at +85°C, and 40µV (max) at +125°C.
o The indirect current-feedback architecture offers true ground sensing and an input common-mode voltage range of -0.1V to VDD - 1.3V. CMRR is 106dB (min).
o The amplifiers are designed for high gain amplification of small differential signals (±100mV) with CMOS, 1pA input bias currents. The MAX4209H (G = 100x) offers gain accuracy of 0.25%( max) at +25°C, 0.3% (max) at +85°C, and 0.35% (max) at +125°C.
o An on-chip, reference buffer amplifier increases system accuracy and allows a simple resistor-divider to set the zero signal, output voltage in single-supply applications.
o These amplifiers are ideal for use in: laptop computers, specifically the core, ASICs, and microprocessor current monitoring; automotive and industrial applications; and medical instrumentation.
SUNNYVALE, CA - December 20, 2007 - Maxim Integrated Products (Pink Sheets: MXIM) introduces 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 MAX 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.
Patented Design Allows Full Use of Input Common-Mode Range
The MAX4208/MAX4209H feature an innovative, two-transconductance-amplifier architecture (see Figure 1). This indirect current-feedback architecture allows customers to utilize the full dynamic range of input differential signals, even when the common-mode voltages are close to, or below, ground. This true low-side sensing capability is not offered by the common three-operational-amplifier approach.
The MAX4208/MAX4209H offer true ground sensing and an input common-mode voltage range of -0.1V to VDD - 1.3V. CMRR is guaranteed to be at least 106dB.
The devices' input stage uses CMOS transistors with 1pA (typ) input bias current. Input offset voltage is 20µV (max) at +25°C, 30µV (max) at +85°C, and 40µV (max) over the 40°C to +125°C temperature range. The offset voltage distribution in Figure 2 shows that the devices' typical input offset voltage is less than 5µV.
Impressive Amplifier Offset and Gain Error Performance
The MAX4208 features an adjustable gain, with the gain set by the ratio of two external resistors (G = 1 + R2/R1). The MAX4209H uses internal laser-trimmed resistors to set a fixed gain of 100x. The MAX4209H has a maximum gain error of ±0.25% at +25°C, ±0.3% up to +85°C, and ±0.35% over the entire -40°C to +125°C temperature range. The gain error histogram in Figure 3 shows that the typical gain error is better than ±0.1%.
The MAX4208/MAX4209H also include an autozero reference-buffer amplifier (see Figure 1), which allows the output to be level-shifted to VDD/2 using a simple resistor-divider or an external reference input with minimum loading error. This buffer increases system accuracy and is useful for bipolar signals in single-supply applications. The high-impedance inputs are optimized for small-signal differential voltages (±100mV). All devices operate from a single 2.85V to 5.5V supply (or ±1.425V to ±2.75V dual supplies) with ground-sensing capability and ultra-low, 1pA (typ) CMOS-input bias currents.
Applications Benefit from the New Technology
The benefits of using the MAX4208/MAX4209H amplifiers can be seen in a wide range of applications. A few examples follow.
1. Resistive and capacitive bridge-transducers that sense pressure and position in automotive and industrial applications (see Figure 4) can be amplified and used to drive analog-to-digital converters (ADCs). The low-offset voltages and low-offset drift allow large gains to be used with small DC error, thus delivering better performance. The CMOS inputs also allow the part to interface to a wide variety of capacitive and other high-impedance sensors.
2. Figure 5 shows the MAX4209H used as an accurate low-side or low-voltage current-sense amplifier with extremely small sense voltages (10mV) and small sense resistors. This design is used in laptops to monitor current in the core, ASIC, and microprocessor. The low VSENSE voltage drop reduces power dissipation in sense resistors to minimize hot spots, which leads to better efficiency.
3. MAX4208/MAX4209H can also be used in multiple medical-instrumentation applications such as cardiac monitors and defibrillators.
Samples of the MAX4208/MAX4209H are available now. The MAX4208 and MAX4209H are priced at $1.65 (1000-up, FOB USA). For more information please visit: http://www.maxim-ic.com/Autozero-Amps
*U.S. Patent #6,559,720.
