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HT66FM5440
Brushless DC Motor A/D Flash MCU
HT66FM5440
Brushless DC Motor A/D Flash MCU
Analog to Digital Converter
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, or internal signals, and
convert these signals directly into a 12-bit or 10-bit digital value.
The six external channels can be individually configured to be isolated using the unity-gain buffer
when connected to the internal A/D converter. This function can avoid transient voltages caused by
channel switching from affecting the channel voltage to be measured. However, in this case the input
voltage is limited in the range of V
SS
+0.1V to V
DD
-0.1V. To convert a full voltage range of 0~V
DD
,
the external channel can be configured to bypass the unity-gain buffer using the BYPSANn bit in the
ADBYPS register.
The three internal channels, which are OPA0, OPA1 and OPA2 outputs, OPA0O~OPA2O, can not
bypass the unity-gain buffer when connected to the A/D converter. This means that any one of
these channels must go through the unity-gain buffer by enabling the UGB_ON bit in the ADBYPS
register, otherwise the conversion result may be incorrect.
There are two trigger mechanisms to start an A/D conversion, one is using the ADSTR bit, another is
using the DLSTR bit. For the ADSTR triggered A/D conversion, the input channel is selected using
the ACS3~ACS0 bits. For the DLSTR triggered A/D conversion, the input channel is selected using
the ADISn3~ADISn0 bits. More detailed information about the A/D input signal is described in the
"A/D Converter Control Registers" section.
External Input Channels
Internal Input Signals
A/D Channel Select Bits
6: AN0~AN3� AN6~AN�
3: OPA0O~OPA�O
ACS3~ACS0�
ADISn3~ADISn0 (n=0~3)
The accompanying block diagram shows the overall internal structure of the A/D converter, together
with its associated registers.