SN8P2977
8-Bit Micro-Controller with Regulator, PGIA, 24-bit ADC
SONiX TECHNOLOGY CO., LTD
Page 104
Version 1.7
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Regulator, PGIA and ADC
13.1 OVERVIEW
The SN8P2977 has a built-in Voltage Regulator to support a stable voltage 2.4V/2.8V/3.2V from pin AVDDR and
0.75V/1.0V/1.5V/2.0V from pin AVE+ with maximum 10mA current driving capacity. The AVDDR provides stable
voltage for internal circuits (PGIA, ADC) and external sensor (load cell or thermistor).
The SN8P2977 series also integrated
Δ Σ
Analog-to-Digital Converters (ADC) to achieve 24-bit performance and up to
2^24-step resolution. The ADC builds in internal Gain Option with selective range of x1 and x2 for additional signal
amplification expect PGIA
.
The PGIA provides of input channel mode: One fully differential input. This ADC is
optimized for measuring low-level unipolar or bipolar signals in weight scale and medical applications. A very low noise
chopper-stabilized programmable gain instrumentation amplifier (PGIA) with selectable gains of 1x, 4x, 8x, 16x, 32x,
64x, 128x and 200x in the ADC to accommodate these applications.
13.2 ANALOG INPUT
Following diagram illustrates a block diagram of the PGIA and ADC module. The front end consists of a multiplexer for
input channel selection, a PGIA (Programmable Gain Instrumentation Amplifier), and the
Δ Σ
ADC modulator.
To obtain maximum range of ADC output, the ADC maximum input signal voltage should be close to but
can’t over the
reference voltage V(R+, R-), Choosing a suitable reference voltage and a suitable gain of PGIA can reach this purpose.
The relative control bits are IRVS bits (Reference Voltage Selection) in ADCM1 register and GS[2:0] bits (Gain
Selection) in AMPM2 register.
+
-
PGIA and ADC Structure
X+
X-
ADC
PGIA
ADC Output 24-Bits
[ADCDH, ADCDM, ADCDL]
Vref (R+/R-)
Int. 0.23V~1.6V
Gain: 1x(Buff) ~200x
Gain (1x, 2x)
Offset
(0,
-
1/4, -1/2, -3/4)xVref
OSR (64~32768)
AVDDR
AVDDR
AVE
ADCKSDIV
ADCKS
Channel Selection
MUXP
AI1
AI2
AI3
AI4
AVE
V)
Tempe)
GND
Channel Selection
MUXN
AI1
AI2
AI3
AI4
AVE
VDD_DET(-)
Temperature(-)
GND
PGIA Off
PGIA Off
Block Diagram of ADC module