HX711 Avia Semiconductor
HX711 Avia Semiconductor
HX711 Avia Semiconductor
DESCRIPTION FEATURES
Based on Avia Semiconductors patented Two selectable differential input channels
technology, HX711 is a precision 24-bit analog- On-chip active low noise PGA with selectable gain
to-digital converter (ADC) designed for weigh of 32, 64 and 128
scales and industrial control applications to On-chip power supply regulator for load-cell and
interface directly with a bridge sensor. ADC analog power supply
The input multiplexer selects either Channel A On-chip oscillator requiring no external
or B differential input to the low-noise component with optional external crystal
programmable gain amplifier (PGA). Channel A On-chip power-on-reset
can be programmed with a gain of 128 or 64, Simple digital control and serial interface:
corresponding to a full-scale differential input pin-driven controls, no programming needed
voltage of 20mV or 40mV respectively, when Selectable 10SPS or 80SPS output data rate
a 5V supply is connected to AVDD analog power Simultaneous 50 and 60Hz supply rejection
supply pin. Channel B has a fixed gain of 32. On-
Current consumption including on-chip analog
chip power supply regulator eliminates the need power supply regulator:
for an external supply regulator to provide analog
normal operation < 1.5mA, power down < 1uA
power for the ADC and the sensor. Clock input is
flexible. It can be from an external clock source, a Operation supply voltage range: 2.6 ~ 5.5V
crystal, or the on-chip oscillator that does not Operation temperature range: -40 ~ +85
require any external component. On-chip power- 16 pin SOP-16 package
on-reset circuitry simplifies digital interface
initialization.
There is no programming needed for the APPLICATIONS
internal registers. All controls to the HX711 are Weigh Scales
through the pins. Industrial Process Control
VAVDD S8550 VSUP
2.7~5.5V
R2 R1
10uF
Load cell VFB BASE VSUP DVDD
AVDD
INA+
Analog Supply Regulator
INA- DOUT
To/From
Digital PD_SCK
Interface
MCU
Input 24-bit
INB+ MUX ADC
PGA RATE
INB- Gain = 32, 64, 128
VBG Internal
Bandgap Reference Oscillator
HX711
0.1uF
AGND XI XO
SOP-16L Package
AVIA SEMICONDUCTOR 2
HX711
KEY ELECTRICAL CHARACTERISTICS
1Settling time refers to the time from power up, reset, input channel change and gain change
to valid stable output data.
Table 2 Key Electrical Characteristics
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HX711
Analog Inputs
Channel A differential input is designed to Output Data Rate and Format
interface directly with a bridge sensors When using the on-chip oscillator, output data
differential output. It can be programmed with a rate is typically 10 (RATE=0) or 80SPS
gain of 128 or 64. The large gains are needed to (RATE=1).
accommodate the small output signal from the
sensor. When 5V supply is used at the AVDD pin, When using external clock or crystal, output
these gains correspond to a full-scale differential data rate is directly proportional to the clock or
input voltage of 20mV or 40mV respectively. crystal frequency. Using 11.0592MHz clock or
crystal results in an accurate 10 (RTE=0) or
Channel B differential input has a fixed gain of 80SPS (RATE=1) output data rate.
32. The full-scale input voltage range is 80mV,
when 5V supply is used at the AVDD pin. The output 24 bits of data is in 2s complement
format. When input differential signal goes out of
the 24 bit range, the output data will be saturated
Power Supply Options at 800000h (MIN) or 7FFFFFh (MAX), until the
Digital power supply (DVDD) should be the input signal comes back to the input range.
same power supply as the MCU power supply.
When using internal analog supply regulator, Serial Interface
the dropout voltage of the regulator depends on Pin PD_SCK and DOUT are used for data
the external transistor used. The output voltage is retrieval, input selection, gain selection and power
equal to VAVDD=VBG*(R1+R2)/ R1 (Fig. 1). This down controls.
voltage should be designed with a minimum of
100mV below VSUP voltage. When output data is not ready for retrieval,
digital output pin DOUT is high. Serial clock
If the on-chip analog supply regulator is not input PD_SCK should be low. When DOUT goes
used, the VSUP pin should be connected to either to low, it indicates data is ready for retrieval. By
AVDD or DVDD, depending on which voltage is applying 25~27 positive clock pulses at the
higher. Pin VFB should be connected to Ground PD_SCK pin, data is shifted out from the DOUT
and pin BASE becomes NC. The external 0.1uF output pin. Each PD_SCK pulse shifts out one bit,
bypass capacitor shown on Fig. 1 at the VBG starting with the MSB bit first, until all 24 bits are
output pin is then not needed. shifted out. The 25th pulse at PD_SCK input will
pull DOUT pin back to high (Fig.2).
Clock Source Options Input and gain selection is controlled by the
By connecting pin XI to Ground, the on-chip number of the input PD_SCK pulses (Table 3).
oscillator is activated. The nominal output data PD_SCK clock pulses should not be less than 25
rate when using the internal oscillator is 10 or more than 27 within one conversion period, to
(RATE=0) or 80SPS (RATE=1). avoid causing serial communication error.
Input
If accurate output data rate is needed, crystal or PD_SCK Pulses Gain
channel
external reference clock can be used. A crystal
can be directly connected across XI and XO pins. 25 A 128
An external clock can be connected to XI pin, 26 B 32
through a 20pF ac coupled capacitor. This
external clock is not required to be a square wave. 27 A 64
It can come directly from the crystal output pin of
the MCU chip, with amplitude as low as 150 mV. Table 3 Input Channel and Gain Selection
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HX711
T2 T3
T1
Next ConversionCH.A, Gain:128
PD_SCK 1 2 3 4 24 25
T4
Fig.2 Data output, input and gain selection timing and control
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HX711
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HX711
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HX711
Reference DriverC
//-------------------------------------------------------------------
sbit ADDO = P1^5;
sbit ADSK = P0^0;
unsigned long ReadCount(void){
unsigned long Count;
unsigned char i;
ADDO=1;
ADSK=0;
Count=0;
while(ADDO);
for (i=0;i<24;i++){
ADSK=1;
Count=Count<<1;
ADSK=0;
if(ADDO) Count++;
}
ADSK=1;
Count=Count^0x800000;
ADSK=0;
return(Count);
}
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HX711
Package Dimensions
9.90 10.10
9.70
6.20
6.00 3.90 4.10
5.80
3.70
1.27 0.48
0.39
1.60
1.20
MAX
Typ Unit: mm
MIN
SOP-16L Package
AVIA SEMICONDUCTOR 9