AK8996 Datasheet, PDF (40/74 Pages) Asahi Kasei Microsystems – Pressure Sensor Interface IC

[AK8996/W]
Referring to the previous calculation example, determine the stabilization time based on actual
requirements:
Prerequisites: Output reference voltage: X
Output voltage (VOUT pin): Y
VO pin external capacitance: Cap (Cap[µF] typ., Cap*1.1[µF] worst)
Internal resistance 1:
Res1 (560[Ω] typ., 689.5[Ω] worst)
VO pin internal resistance 2: Res2 (32[kΩ] typ., 39.4[kΩ] worst)
Item C:
Y>A*X C=99.5[%]; Y<A*X C=100.5[%]
Period in the figure:
Time (0.3[msec] typ., 0.2 or 0.5[msec] worst)
Settling factor A=(1-e^(-Time/(Res1*Cap)))*100
Settling factor B=(C[%]/100*Y-A/100*X)/(Y-A/100*X)*100
Settling time D (period in the figure) =-Res2*Cap*ln(1-B/100)
99.5% settling time (period + in the figure) = Time + D
VDD pin voltage
S am ple tim in g
VO&VOUT pin voltage
e.g. Level shift voltage 0.5VDD Final value 0.1*VDD
When sampling frequency is 100 Hz,
VO pin capacitance 3 µF
- Reference designators
: Sam pling tim in g; th is diagram represents 1 00 Hz (10 msec).
: Powe r-up rise t ime (Tvdd), specified as less than 200 µs.
: Sett ling time for stable a nalog op eration (Ten able 1, 2).
Spe cified as e ith er less than 46 5µs or 495µs depe nding on whethe r STBY N p in is used o r not.
: Pressure sign al dete ction tim e. On p ower-up o r after exiting t he STBY N mode, this sig nal rapidly settles do wn to the re ference voltag e.
This tim e finally settles down depending on the VO pin e xternal cap acita nce an d the int ernal 32kΩ resistance dependan t tim e consta nt.
In this case, this p eriod is typically 345.2 msec as shown in the table be low.
VO pin
Ext. cap
Cutoff
Freq.
(typical)
Fig Time (fixed)
Typical
case
Worst
case
Note)
99.5% Settling time
(Fig )
Typical
case
Worst
case
Note)
99.5% Settling time
(Fig + )
Typical
case
Worst case
Note)
3µF 1.658Hz 0.3 msec 0.2 msec 345.2 msec 617.9 msec
1µF 4.974Hz 0.3 msec 0.5 msec 171.8 msec 244.6 msec
100nF 49.74Hz 0.3 msec 0.5 msec 21.37 msec 28.96 msec
10nF 497.4Hz 0.3 msec 0.5 msec 2.139 msec 2.897 msec
1nF 4.97kHz 0.3 msec 0.5 msec 0.214 msec 0.290 msec
500pF 9.95kHz 0.3 msec 0.5 msec 0.107 msec 0.145 msec
Note) Worst case for external capacitance ±10% and lot variations.
345.5 msec
172.1 msec
21.67 msec
2.439 msec
0.514 msec
0.407 msec
618.1 msec
245.1 msec
29.46 msec
3.397 msec
0.790 msec
0.645 msec
MS1055-E-02
40
2011/12