Rev. 1.10
134
October 23, 2020
Rev. 1.10
135
October 23, 2020
BC66F5652
2.4GHz RF Transceiver A/D Flash MCU
BC66F5652
2.4GHz RF Transceiver A/D Flash MCU
Bit 3~2
SAVRS1~SAVRS0
: A/D converter reference voltage selection
00: Internal A/D converter power, AV
DD
01: External VREF pin
1x: Internal PGA output voltage, V
R
These bits are used to select the A/D converter reference voltage source. When the
internal reference voltage source is selected, the reference voltage derived from the
external VREF pin will automatically be switched off.
Bit 1~0
PGAGS1~PGAGS0
: PGA gain select
00: Gain=1
01: Gain=1.667 – V
R
=2V as V
RI
=1.2V
10: Gain=2.5 – V
R
=3V as V
RI
=1.2V
11: Gain=3.333 – V
R
=4V as V
RI
=1.2V
These bits are used to select the PGA gain. Note that here the gain is guaranteed only
when the PGA input voltage is equal to 1.2V.
• VBGRC Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
—
—
—
VBGREN
R/W
—
—
—
—
—
—
—
R/W
POR
—
—
—
—
—
—
—
0
Bit 7~1
Unimplemented, read as “0”
Bit 0
VBGREN
: Bandgap reference voltage control
0: Disable
1: Enable
This bit is used to enable the internal Bandgap reference circuit. The internal Bandgap
reference circuit should first be enabled before the V
BGREF
voltage is selected to be
used. A specific start-up time is necessary for the Bandgap circuit to become stable and
accurate.
A/D Converter Reference Voltage
The actual reference voltage supply to the A/D Converter can be supplied from the internal A/D
converter power, AV
DD
, an external reference source supplied on pin VREF or an internal reference
voltage V
R
determined by the SAVRS1~SAVRS0 bits in the SADC2 register. The internal reference
voltage is amplified through a programmable gain amplifier, PGA, which is controlled by the
ADPGAEN bit in the SADC2 register. The PGA gain can be equal to 1, 1.667, 2.5 or 3.333 and
selected using the PGAGS1~PGAGS0 bits in the SADC2 register. The PGA input can come from
the external reference input pin, VREFI, or an internal Bandgap reference voltage, V
BGREF
, selected
by the PGAIS bit in the SADC2 register. As the VREFI and VREF pin both are pin-shared with
other functions, when the VREFI or VREF pin is selected as the reference voltage pin, the VREFI
or VREF pin-shared function selection bits should first be properly configured to disable other
pin-shared functions. However, if the internal reference signal is selected as the reference source,
the external reference input from the VREFI or VREF pin will automatically be switched off by
hardware.
Note that the internal Bandgap reference circuit should first be enabled before the V
BGREF
is selected
to be used. A specific start-up time is necessary for the Bandgap circuit to become stable and
accurate.