Vicom Systems FC-FC3 Manual de usuario descargar pdf (Pagina 8)

CONFIDENTIAL [AK8999A/AW/AD]

MS1600-E-00 2014/05

- 8 -

Block

Functions

STV

VDD track

Gain_Temp.

(STV)

Supply voltage and sensitivity temperature variation compensation circuit.

The pressure sensor sensitivity temperature drift and the supply voltage variation are

compensated by using the magnitude of supply voltage variation and the preloaded

compensation data in the EEPROM.

Sensitivity temp. drift. adj. Adj. range -4000ppm/ ºC to +2500ppm/ ºC

Adj. step 18ppm/ ºC step

LPF

Anti-alia

sing filter to eliminate the aliasing noise generated in the next sample and hold

circuit (S/H). The cutoff frequency is fc=60kHz.

S/H &

Level Shift

& SCF

S/H doubles the LPF output and samples and holds it. The output reference voltage can be

changed.

Output reference voltage adj. Adj. range 0.02*VDD to 0.98*VD

Adj. step 0.002*VDD /step

SCF is a low-pass filter without using the external capacitors. The cutoff frequency (fc:

1kHz /500Hz /250Hz) of the filter can be set by EEPROM.

Buffer

& SMF

Buffe

r to provide 1.111x output and produce a band limited output with low impedance.

146kΩ internal resistance and an external capacitor (C) make the LPF characteristics.

Change the external capacitance value according to the desired signal band for detection

using the following equation:

fc=1/(2*π* 146kΩ*C) (Hz)

SMF is a low-pass filter (fc=10kHz) for eliminating the clock noise generated by the

previous SCF. SMF is switched on or off in combination with the previous stage SCF

using the EEPROM data.

Timing

Logic

Generates timing sync signals for internal operation and sampling frequencie

s for sensor

output signals.

Sampling frequency (fs): 0.83kHz or 8.33kHz

Regulator

Constant voltage generator to drive the sensor. The drive voltage can be selected from

the EEPROM depending on the supply voltage being used.

Drive voltage: 2.2V@VDD:3, 3.3V ± 10%, 4.0/2.2V@VDD:5V ± 10%

Pressure

Threshold

Detector1/2

Two sets of pressure threshold detectors.

The pressure threshold

detection range can be individually selected depending on the EEPROM

data.

• Pressure above a certain value is detected

• Pressure below a certain value is detected

The DET1 and DET2/PTH pins go high when the detected pressure exceeds the threshold (the

polarity change by EEPROM is possible). The detection threshold can be set by the input of

DET2/PTH pin (in this case, Pressure Threshold Detector 2 cannot use) or using the EEPROM

data. The hysteresis voltage can be adjusted at 2 bits, and it varies ratiometrically with

respect to the supply voltage as well as the detection threshold.

Note) The exact pressure determination cannot be achieved until the VOUT pin output is

stabilized after power-up.

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