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PDF HI-8437 Data sheet ( Hoja de datos )
| Número de pieza | HI-8437 | |
| Descripción | 32-Channel High Impedance Low Threshold Sensor | |
| Fabricantes | HOLTIC | |
| Logotipo |  |
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January 2016
HI-8437
32-Channel High Impedance
Low Threshold Sensor with SPI Interface
GENERAL DESCRIPTION
The HI-8437 is a 32-channel high impedance discrete-to-
digital sensor fabricated with Silicon-on-Insulator (SOI)
technology designed to interface with a Serial Peripheral
Interface (SPI).
The four banks of 8 sense inputs can be programmed to
detect one of two threshold ranges, VTHR1, VTHR2.
All sense inputs have a 400KΩ resistor to ground and are
internally lightning protected to DO160G, Section 22, Cat
AZ, BZ and ZZ without external components.
The sensing circuit window comparator thresholds are set
by programming the center threshold and hysteresis
registers to values from 0.4V to 5.2V. The digital values of
the sensed inputs can be read either one bank at a time or
all 4 banks with one command.
Interface to the digital subsystem is simple CMOS logic
inputs and outputs. The logic pins are compatible with 3.3V
logic allowing direct connection to a wide range of
microcontrollers or FPGAs.
FEATURES
· Robust CMOS Silicon-on-Insulator (SOI) technology
· 32-channel Programmable Sense Operation, two
programmable threshold ranges, 4 X 8 Input Sensors
· Programmable HI/LO Threshold and Hysteresis in
0.1V steps, from 0.4V to 5.2V.
· Single Low Voltage Supply Operation
· Logic Operation from 3.0V to 3.6V
· 20 MHz Serial Peripheral Interface (SPI)
· Lightning Protected Sense Inputs
· Internal Self-Test
PIN CONFIGURATIONS
NC - 1
SENSE_0 - 2
SENSE_1 - 3
SENSE_2 - 4
SENSE_3 - 5
SENSE_4 - 6
SENSE_5 - 7
SENSE_6 - 8
SENSE_7 - 9
SENSE_8-10
SENSE_9-11
HI-8437PQI
HI-8437PQT
HI-8437PQM
33 - SENSE_27
32 - NC
31 - SENSE_26
30 - SENSE_25
29 - SENSE_24
28 - SENSE_23
27 - SENSE_22
26 - SENSE_21
25 - SENSE_20
24 - SENSE_19
23 - SENSE_18
44 Pin Plastic Quad Flat Pack (PQFP)
10mm x 10mm
NC - 1
SENSE_0 - 2
SENSE_1 - 3
SENSE_2 - 4
SENSE_3 - 5
SENSE_4 - 6
SENSE_5 - 7
SENSE_6 - 8
SENSE_7 - 9
SENSE_8 -10
SENSE_9 -11
HI-8437PCI
HI-8437PCT
HI-8437PCM
33 - SENSE_27
32 - NC
31 - SENSE_26
30 - SENSE_25
29 - SENSE_24
28 - SENSE_23
27 - SENSE_22
26 - SENSE_21
25 - SENSE_20
24 - SENSE_19
23 - SENSE_18
APPLICATION
· Avionics Discrete to Digital Sensing
· Low thresholds applications.
44 Pin Plastic QFN
7mm x 7mm
(DS8437 Rev. A)
HOLT INTEGRATED CIRCUITS
www.holtic.com
01/16
1 page  
HI-8437
Note: SPI Instruction op-codes not shown in Table 2 are
“reserved” and must not be used. Further, these op-codes will
not provide meaningful data in response to a read instruction.
Two instruction bytes cannot be “chained”; nCS must be
negated after each instruction, and then reasserted for the
following Read or Write instruction.
SCK
0 1234567 0 1234567
MSB
SI
High Z
SO
Op-Code Byte
LSB
MSB
nCS
Data Byte 0
LSB
High Z
FIGURE 5. Single-Byte Read From a Register
0 1234567 0 1234567 0 1234567
SCK
SPI Mode 0
MSB
SI
LSB MSB
LSB MSB
LSB
High Z
SO
Op-Code Byte
Data Byte 1
Data Byte 0
nCS
FIGURE 6. 2-Byte SPI Write Example
012345670123456701234567 01234567 01234567
SCK
SPI Mode 0
MSB
LSB MSB
LSB MSB
LSB MSB
LSB MSB
LSB
SI
High Z
SO
Op-Code Byte
Data Byte 3
Data Byte 2
Data Byte 1
Data Byte 0
nCS
FIGURE 7. 4-Byte SPI Read Example
HOLT INTEGRATED CIRCUITS
5
5 Page 
HI-8437
FUNCTIONAL DESCRIPTION
OVERVIEW
FUNCTION TABLE
Table 14. Function Table
The HI-8437 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 with one of two threshold ranges, VTR1 or
VTR2. The state of each sensor can be read out through the
SPI.
SENSE_n
> VT1HI
Open or < VT1LO
PSEN_n
L (VTR1)
L (VTR1)
SO_n
L
H
The VTR1 high/low thresholds can be programmed
independently of the VTR2 high/low thresholds. Table 14
summarizes basic function selection and Table 16 gives
more details on possible threshold values.
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.
> VT2HI
H (VTR2)
Open or < VT2LO
H (VTR2)
H = VLOGIC, L = GND
VTHI = Threshold Center Value + ½ Hsyteresis
VTLO = Threshold Center Value - ½ Hysteresis
L
H
NOTE: 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 must be in a high or low state prior to and
during each re-programming cycle. See also section on Test
Mode.
INITIALIZATION AND RESET
The HI-8437 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 CNTRL<1>. This reset is the same as the full reset
except the part is held in the reset mode until the
CNTRL<1> bit is written back to a “0”.
PROGRAMMING THRESHOLDS
The HI-8437’s on-chip DAC takes the 6-bit programmed
center and hysteresis values from the Threshold Center
Value and Hysteresis Registers (VTR1CENHYS and
VTR2CENHYS) 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 for each threshold range.
b) VTRnHYS = (VTHI - VTLO) / (0.2V/LSB).
c) VTRnCVAL = (VTHI + VTLO)/2 / (0.1V/LSB)
d) Program the registers.
CONFIGURATION
The user configures the HI-8437 for specific applications by:
1) Programming the sensor threshold range for each of the
4 banks.
2) Convert the required VTHI and VTLO into center and
hysteresis values as shown in example below.
HOLT INTEGRATED CIRCUITS
11
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet HI-8437.PDF ] | |
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