AK8999A Datasheet, PDF (7/68 Pages) Asahi Kasei Microsystems – Pressure Sensor Control IC

CONFIDENTIAL
[AK8999A/AW/AD]
5. Block Diagram and Functions
VS
Regulator
VDD
V_Bandgap
V_Reference
I_Reference
EXTMP
V_Temp.
(internal or
external)
Gain Temp.
track
Offset Temp.
track
VDD track
STV
Oscillator
Timing
Logic
Power ON
Reset
V_
Common
VOUT
EEPROM
Pressure Detector 2
Pressure Detector 1
Offset_Temp. Gain_Temp.
LPF
VP
Gain Amp.1 Gain Amp.2 Gain Amp.3
VN
S/H & SCF
& Level Shift
Buffer
& SMF
Offset
Gain
EEPROM
SDI/O
Gain Amplifier Block
&
Control
Serial I/F
Register
VDD
VSS
DET2 / PTH
DET1
VO
VOUT
CSCLK
Gain Amplifier Block, LPF, S/H&SCF& Level shifter, Buffer & SMF
The set of these blocks amplifies, compensates and outputs the pressure sensor signal.
The circuits from Gain Amplifier to S/H amplify, compensate, sample and hold the pressure sensor
output by time sharing. The output stage, with an internal resistor of 146kΩ, band-limited with an
external capacitor on VO pin, can provide a low impedance output via buffer. By enabling SCF and
SMF, band limit can be done, eliminating the need for the external capacitors. The output reference
voltage can be set with an integrated level shifter. Percentage indications define a 4800mVdc output as
100%, which is 60times magnified level of 80mVdc differential input.
Block
Gain Amp.
1/2/3
Gain
(G1/2/3)
Offset_Temp.
Offset
Offset Temp.
track
(G2)
Functions
Gain Amp.1 is a low-noise high-gain amplifier at the front. The differential signal is
amplified by a factor of 10x typ. (5x to 70x).
Gain Amp.2 converts the G1 differential output to single-ended with reference to
0.5*VDD and amplifies by a factor of 1.5x typ. (or 3.0x).
Gain Amp.3 amplifies by a factor of 1.8x typ. (or 3.0x).
Span voltage is adjusted with G1/2/3 Gain (G1/2: coarse adjustment, G3: fine
adjustment).
The pressure sensor offset voltage and offset temperature drift are compensated by using
the preloaded compensation data in the EEPROM. The following value is converted into
the input value at @5.0V.
Offset adj.
Adj. range
Coarse: ±13 to ±373mV
Fine: ±1 to ±34mV
Adj. step
Coarse: 2 to 53mV /step
Fine: 0.01 to 0.27mV /step
Offset temp. drift. adj.
Adj. range
±0.04 to ±1.23mV/ ºC
Adj. step
0.2 to 4.8μV/ºC step
MS1600-E-00
-7-
2014/05