AK8996 Datasheet, PDF (47/74 Pages) Asahi Kasei Microsystems – Pressure Sensor Interface IC

[AK8996/W]
9) Note on the AK8996 Power-up
When applying the power to the AK8996, use caution to the following.
On power up the AK8996, keep the rise time below 200µs (0.1*VDD -> 0.8*VDD). If the rise time on
power up exceeds 200µs, this section may enter the test mode. The AK8996 may not function
properly in the test mode. To exit from the test mode, reset at the STBYN pin or recycle the power.
If the AK8996 cannot be powered up in less than 200µs, connect the STBYN pin to the resistor (R) and
capacitor (C) as shown below. Determine the resistance (R) and capacitance (C) values so that the
STBYN pin voltage is 0.3*VDD or less when the supply voltage reaches the VDD to ensure the
AK8996 digital circuit is reset on power up.
The following equation is used to calculate the resistance (R) and capacitance (C) values.
Vstbyn = VDD * [1-exp(-t/R*C)]
Vstbyn : STBYN pin voltage
t
: Time required to reach Vstbyn voltage
VDD
EEPROM &
Control Register
Serial I/F
R
STBYN
C
VSS
10) Note on the pressure detection circuit hysteresis voltage setup
Use caution to the following when setting up the pressure detection circuit hysteresis voltage.
The hysteresis voltage is normally used as negative with respect to the pressure detection threshold value
reference. If, however, the hysteresis voltage is set to a low value (e.g. 0.0025*VDD), the hysteresis
voltage may be positive with respect to the pressure detection threshold reference. In that case, the
pressure detection circuit may not function properly.
To avoid the above situations, be sure to adjust the hysteresis voltage in the adjustment phase before
using the pressure detection circuit hysteresis voltage. Also note that the hysteresis voltage varies with
the supply voltage.
The hysteresis voltages for four different supply voltages (2.5V, 3.0V, 3.3V, 5V) are shown in the table
below. Regions in the table where hysteresis voltage is likely to be inverted are shaded in red and the
regions the voltage is the least likely to be inverted are shaded in blue. Note that the table in the below is
for reference purpose only; do not use it as being guaranteed.
Address : 11 hex D[2:0]=EHYS[2:0]
EHYS[2:0]
VDD
Dec Hex Bin ^Reference VDD:2.5V
0 0 000 0.0200*VDD -50.00
1 1 001 0.0175*VDD -43.75
2 2 010 0.0150*VDD -37.50
3 3 011 0.0125*VDD -31.25
4 4 100 0.0100*VDD -25.00
5 5 101 0.0075*VDD -18.75
6 6 110 0.0050*VDD -12.50
7
7 111 0.0025*VDD
-6.25
Hysteresis voltage (mV)
VDD:3V VDD:3.3V
-60.00
-52.50
-45.00
-37.50
-66.00
-57.75
-49.50
-41.25
-30.00
-33.00
-22.50
-24.75
-15.00
-16.50
-7.50
-8.25
VDD:5V
-100.0
-87.5
-75.0
-62.5
-50.0
-37.5
-25.0
-12.5
units
mV
mV
mV
mV
mV
mV
mV
mV
MS1055-E-02
47
2011/12