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HI-8436 Datasheet(PDF) 11 Page - Holt Integrated Circuits |
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HI-8436 Datasheet(HTML) 11 Page - Holt Integrated Circuits |
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11 / 21 page  FUNCTIONAL DESCRIPTION HI-8436 HOLT INTEGRATED CIRCUITS 11 OVERVIEW The HI-8436 is comprised of 32 sensors arranged in 4 banks of 8 inputs, easily accessible via a four wire SPI communication bus. Each bank of sensors can be programmed as either GND/Open or Supply/Open. The state of each sensor can be read out through the SPI. The GND/Open high/low thresholds can be programmed independently of the Supply/Open high/low thresholds. An internal test mode is available which sets the input to each sensor comparator to the test value as programmed by the Test Mode Data Register. Certain safety-critical flight applications require periodic sensor testing or register re-programming during flight. If programmable registers are periodically re-written, the sensor inputs be in a high or low state prior to and during each re-programming cycle. See also section on Test Mode. must Table 14 summarizes basic function selection and Table 16 gives more details on possible threshold values. The HI-8436 generates a full reset upon application of power. This power-on-reset (POR) sets all registers to their default values. The part can also be initialized to the full reset state by applying a 100ns active low pulse to the external nMR pin. A software reset is also possible via the SPI by writing a “1” to CTRL<1>. This reset is the same as the full reset except the part is held in the reset mode until the CTRL<1> bit is written back to a “0”. The user configures the HI-8436 for specific applications by: 1) Programming the sensor type for each of the 4 banks. 2) Convert the required VTHI and VTLO into center and hysteresis values as shown in example below. 3) For GND/Open sensors, VWETn must be set greater than VTHI/0.9 + 2.75V. NOTE: INITIALIZATION AND RESET CONFIGURATION PROGRAMMING THRESHOLDS GND/OPEN SENSING The HI-8436’s on-chip DAC takes the 6-bit programmed center and hysteresis values from the Threshold Center Value and Hysteresis Registers (GOCENHYS and SOCENHYS) and converts them to VTHI and VTLO values. Maximum and minimum values may be found in Table 16. The gain of the DAC is 0.1V per LSB. VTHI = center value + ½ hysteresis VTLO = center value - ½ hysteresis To program the thresholds: a) Select VTHI and VTLO. b) Hysteresis = (VTHI - VTLO) / (0.2V/LSB) c) Center Value = (VTHI - VTLO)/2 / (0.1V/LSB) d) Program the register. For GND/Open sensing, the PSENn bit is set to 0. Referring to the Block Diagram, Figure 2, this selection will connect a 3.3k pull-up resistor through a diode to VLOGIC. This resistor gives extra noise immunity for detecting the open state while providing relay wetting current. T he user programs t he desired threshold/hysteresis levels and then determines the open input voltage to set VWETn. To assist the internal pull up current in GND/Open mode an external DC voltage of +7V to +36V should be applied to the VWETn pin. Ω SENSE_n PSEN_n SO_n VWET_n Open or > VTHI L (GND/OPEN) L ** < VTLO L (GND/OPEN) H ** Open or < VTLO H (V+/OPEN) H open > VTHI H (V+/OPEN) L open H = VLOGIC, L = GND VTHI = Threshold Center Value + ½ Hsyteresis VTLO = Threshold Center Value - ½ Hysteresis **For GND/Open applications with thresholds > VLOGIC use VWETn VWETn > VTHI/0.9 + 2.75V FUNCTION TABLE Table 14. Function Table |
Similar Part No. - HI-8436_16 |
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Similar Description - HI-8436_16 |
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