LHA7668-8SFQJ

LHA7668-8 is a low-power, low-noise, highly integrated analog front end suited for high-precision measurement applications. The device integrates a low-noise 24-bit Σ-Δ ADC that can be configured via registers to provide 8 differential inputs or 15 single-ended or pseudo-differential inputs. The LHA7668-4 provides 4 differential input pairs or 7 single-ended or pseudo-differential inputs. An on-chip low-noise programmable gain amplifier allows small signals to be applied directly to the ADC. One of the key advantages of the LHA7668-8/-4 is the flexibility to choose from three integrated power modes. Power consumption, output data rate range, and RMS noise can be tailored through the selected power mode. The device also offers multiple filter options to provide maximum flexibility for users. At an output data rate of 25 SPS (single-cycle settling), the LHA7668-8/-4 achieves simultaneous 50 Hz and 60 Hz rejection, with rejection performance exceeding 80 dB at lower output data rates. The LHA7668-8/-4 is an ultra-highly integrated signal chain solution. The device integrates a precision low-noise, low-drift bandgap voltage reference, and also supports internally buffered external differential reference input. Other key integrated features include programmable low-drift excitation current sources, burnout currents, and a bias voltage generator that can set the common-mode voltage of any channel to AVDD/2. A low-side power switch allows users to power down bridge sensors between conversions, ensuring absolute minimum system power consumption. The device also allows users to select between internal and external clock operation. The built-in channel sequencer can enable multiple channels simultaneously; the LHA7668-8/-4 performs conversions sequentially across all enabled channels, simplifying communication with the device. Up to 16 channels can be enabled at any time, with analog input or diagnostic functions (such as supply monitoring or reference check). This unique feature allows diagnostics and conversions to be interleaved. The LHA7668-8/-4 also supports independent per-channel configuration. The device supports 8 configurations, each comprising gain, filter type, output data rate, buffering, and reference source. The LHA7668-8/-4 also integrates comprehensive diagnostic features, including CRC, signal chain check, and serial interface check, providing a more robust solution. These diagnostic features reduce the external components required to perform diagnostic functions, thereby reducing board space requirements, shortening design time, and saving cost. Per IEC 61508, failure mode and diagnostic analysis (FMEDA) for typical applications indicates a safe failure fraction (SFF) greater than 90%.

Applications

• Temperature measurement
• Pressure measurement
• Industrial process control instrumentation smart transmitters

Key features

• 3 power modes
• RMS noise: Low power: 19 nV rms (1.17 SPS), gain = 128 (typical LHA7668: 195 µA / LHA7668B: 183 µA); Mid power: 15 nV rms (2.34 SPS), gain = 128 (typical LHA7668: 280 µA / LHA7668B: 260 µA); Full power: 20 nV rms (9.4 SPS), gain = 128 (typical LHA7668: 810 µA / LHA7668B: 750 uA)
• Noise-free resolution up to 22 bits in all power modes (= 1, 2, 4, 8)
• Output data rate: Full power: 9.38 SPS to 38,400 SPS; Mid power: 2.34 SPS to 9600 SPS; Low power: 1.17 SPS to 4800 SPS
• Rail-to-rail analog inputs
• Simultaneous 50 Hz/60 Hz rejection (25 SPS, single-cycle settling)
• Diagnostic functions (facilitates SIL certification)
• Crosspoint multiplexed analog inputs: 8 differential/15 pseudo-differential inputs
• Programmable gain (1 to 128)
• Bandgap voltage reference, max drift 10 ppm/°C
• Programmable matched excitation current sources
• Internal clock oscillator
• On-chip bias voltage generator
• Low-side power switch
• General-purpose output (GPO)
• Multiple filter options
• Internal temperature sensor
• Self-calibration and system calibration sensor open-circuit detection
• Auto channel sequencer
• Per-channel independent configuration
• Supply: 2.7 to 5.5 V and ±1.8 or ±2.5 V
• Separate interface supply
• Temperature range: -40°C to +125°C
• 32-lead QFN, 24-lead TSSOP
• 3-wire or 4-wire serial interface: SPI, QSPI, MICROWIRE, and DSP compatible; SCLK pin with built-in Schmitt trigger
• ESD: 4 kV