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Instrumentation amp comes with on-chip diagnostics

Posted: 16 Apr 2010 ?? ?Print Version ?Bookmark and Share

Keywords:instrumentation amplifier? on-chi diagnostic? motor control?

LMP8358 amplifier

National Semiconductor Corp. has launched the LMP8358 zero-drift, programmable instrumentation amplifier with on-chip diagnostics.

The LMP8358 simplifies pressure and thermocouple bridge measurements by allowing users to detect shorts, open circuits and degraded source connections in remote industrial applications. This diagnostic capability prevents circuit shutdowns in medical instruments, precision weigh scales, pressure sensors and motor control systems.

The LMP8358 uses patented techniques to measure and continuously correct its input offset voltage (5?V typical), eliminating offset drift over time and temperature, as well as the effect of 1/f noise. This leads to a flat noise spectrum of 27nV/sqrt Hz. The LMP8358's programmable frequency compensation enables programmable bandwidths, and its offset compensation circuit does not introduce distortion and aliasing for signals lower than 12kHz of bandwidth.

The LMP8358 is equipped with EMI suppression filters to reduce unwanted RF interference from external sources, such as cell phones or nearby antennas. Additional filtering can be added with one external capacitor. The LMP8358 is built on National's CMOS7-5V process technology and provides an optimized signal path solution for precision systems when combined with the 16bit ADC161S626 or 14bit ADC141S626 ADCs.

The LMP8358 provides glitch-free transitions between gain settings, which can be programmed to 10, 20, 50, 100, 200, 500 or 1000 through a SPI or parallel interface. All gain settings have less than 0.1 percent typical gain error. This enables manufacturers to perform system calibration by applying specific signal levels at various gains and temperatures. The LMP8358's gain can be set to an arbitrary value using two external resistors.

Supplied in 14-pin SOIC and 14-pin TSSOP packages, the LMP8358 operates from a single 2.7V to 5V supply and operates over a wide temperature range of -40C to 125C. The amplifier provides 10?V maximum offset voltage and 50nV/C maximum offset voltage drift. It features a gain bandwidth (GBW) of 8MHz while consuming only 1.7mA of supply current. A power-conserving shutdown mode reduces current consumption to less than 1?A. The LMP8358's registers allow designers to program the chip's bandwidth, shutdown and fault detection circuitry. Designers also can daisy chain multiple LMP8358 ICs.

The LMP8358's ground-sensing CMOS input provides a high common-mode rejection ratio of 120dB. It's capable of sensing differential input voltages in a common-mode range that extends from 100mV below the negative supply to 1.4V below the positive supply. This makes the LMP8358 well-suited for interfacing with ground-referenced sensors, supply-referenced sensor bridges and any other application requiring precision and long-term stability.

The LMP8358 is available for $2.71 each in 1K quantities.

Availability: Now.

- eeProductCenter

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