BH67F2260 Datasheet, PDF (137/253 Pages) Holtek Semiconductor Inc – R-Sensor Blood Pressure Meter Flash MCU with LCD

BH67F2260/BH67F2270
R-Sensor Blood Pressure Meter Flash MCU with LCD
SCFCKD Register
Bit
Name
R/W
POR
7
SCFCKD7
R/W
0
6
SCFCKD6
R/W
0
5
SCFCKD5
R/W
0
4
SCFCKD4
R/W
0
3
SCFCKD3
R/W
0
2
SCFCKD2
R/W
0
1
SCFCKD1
R/W
0
0
SCFCKD0
R/W
0
Bit 7~0
SCFCKD7~SCFCKD0: The SCF PGA circuit clock divider.
The SCF PGA clock should be around 488Hz.
The fSCF clock can be divided by 1~256 using these 8 bits.
Following the below equation: SCF PGA clock = fSCF / (SCFCKD+1)
Sensor Constant Current Generator Circuit
These devices include a constant current generator for driving the pressure bridge sensor. This is
formed using a programmable voltage reference and an operational amplifier.
Constant Current Generator Operation
The constant current generator must be first enabled by setting the CCVREFEN bit in the CCVREFC
register high. If cleared to zero then the circuits will be powered down, which will be an important
consideration in battery powered equipment. The constant current reference voltage circuit output
can be selected to be between 0.2V~0.95V, in intervals of 0.05V, providing 16 selections using the
CCVREF3~CCVREF0 bits in the CCVREFC register. This voltage is available on pin CCVREF
to which a capacitor should be connected for stabilisation purposes. This voltage is provided to the
positive input of an internal operational amplifier. By connecting an external resistor to the negative
operational amplifier input, a constant current can be setup.
CCVREFEN
Power: VOREG
CCVREF
CCVIN
CCVIP
VCCREF
0.2V~0.95V
+
OPA
-
Constant Current Generator Block Diagram
Pressure Sensor Constant Current Control Register
CCVREFC Register
Bit
7
6
5
4
3
2
1
0
Name CCVREFEN BATDEN ADACCM
—
CCVREF3 CCVREF2 CCVREF1 CCVREF0
R/W
R/W
R/W
R/W
—
R/W
R/W
R/W
R/W
POR
0
0
0
—
0
0
0
0
Bit 7
CCVREFEN: Sensor constant current circuit enable/disable control
0: Disable
1: Enable
When this bit is equal to “0”, the constant current circuit, including constant current
Rev. 1.00
137
March 15, 2017