BH66F2470 Datasheet, PDF (125/223 Pages) Holtek Semiconductor Inc – Glucose Meter Flash MCU

BH66F2470
Glucose Meter Flash MCU
Analog to Digital Converter – ADC
The need to interface to real world analog signals is a common requirement for many electronic
systems. However, to properly process these signals by a microcontroller, they must first be
converted into digital signals by A/D converters. By integrating the A/D conversion electronic
circuitry into the microcontroller, the need for external components is reduced significantly with the
corresponding follow-on benefits of lower costs and reduced component space requirements.
A/D Converter Overview
This device contains a multi-channel analog to digital converter which can directly interface to
external analog signals, such as that from sensors or other control signals and convert these signals
directly into a 12-bit digital value. It also can convert the internal signals, such as internal OPA
output voltage or DAC output voltage, into a 12-bit digital value. The external or internal analog
signal to be converted is determined by the SAINS2~SAINS0 bits together with the SACS3~SACS0
bits. When the external analog signal is to be converted, the corresponding pin-shared control bits
should first be properly configured and then the desired external channel input should be selected
using the SAINS2~SAINS0 and SACS3~SACS0 bits. Note that when the internal analog signal is
to be converted, the pin-shared control bits should also be properly configured except the SAINS
and SACS bit fields. More detailed information about the A/D input signal is described in the "A/D
Converter Control Registers" and "A/D Converter Input Signals" sections respectively.
External Input Channels
4: AN0~AN3
Internal Signal
4: OPS0, OPS1, OPS2, VDACO
A/D Channel Select Bits
SAINS2~SAINS0,
SACS3~SACS0
The accompanying block diagram shows the overall internal structure of the A/D converter, together
with its associated registers.
Pin-shared
Selection
AN0
AN1
AN2
AN3
SACS3~SACS0
SACKS2~SACKS0
fSYS
÷ 2^N
(N=0~7)
A/D Clock
VDD
ADCEN
VSS
A/D Converter
ADRFS
SADOL _{A/D Data}
SADOH ^Registers
A/D Reference
Voltage
SAINS2~SAINS0
START ADBZ ADCEN
VREF
OPS0
OPS1
OPS2
V_DACO
SAVRS1~SAVRS0
Pin-shared
Selection
VDACVREF V_DD
Note: When the OPSn (n=0~2) option is selected, the actual analog signal is the OPA output voltage,
which is implemented using the OPSn pin. Details are described in the Operational Amplifier
chapter.
A/D Converter Structure
Rev. 1.00
125
March 15, 2017