CMOSTEK CMT2380F17, Manual

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CMT2380F17
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27
Internal Voltage Reference (IVR, 1.4V)
The IVR can be used as the reference voltage of the ADC. The typical output is 1.4V. It can be disabling
by IVREN.
27.1 IVR (1.4V) Structure
Figure 25-1. IVR Diagram
27.2 IVR Register

PCON3
：
Power Control Register 3
SFR Page = P Only
SFR Address = 0x45
Bit
7 6 5 4 3 2 1 0
Name
IVREN -- -- -- -- -- -- --
R/W
R/W W W W W W W W
Reset Value
0 0 0 0 0 0 0 0
Bit 7: IVREN, Internal Voltage Reference Enable.
0: Disable on-chip IVR (1.4V).
1: Enable on-chip IVR (1.4V).
Bit 6~0: Reserved. Software must write “0” on these bits when PCON3 is written.
。
27.3 How to read IVR (1.4V) ADC Prestored value
IVR had been trimmed @VDD=3.3V in factory. And its ADC value had been stored in reserved area in
Flash ROM for customer calculation the voltage value from the ADC value. It means customer
don’t needs to
do the calibration of the ADC in the production line. It can save the test time and cost. Please reference the
following sample code to read the prestored IVR ADC value. And reference 26.2.11 How to improve ADC
Accuracy to understand how to improve ADC measurement accuracy.
void Get_Prestored_IVR(void)
{
ISPCR = ISP_ENABLE;
BOREV = 0x22;
IFMT = 0x06;
IFADRH = 0x00;
IFADRL = 0xC0;