Data Sheet

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HX711

TEL:

(592) 252-9530 (P. R. China)

AVIA SEMICONDUCTOR

EMAIL:

market@aviaic.com

24-Bit Analog-to-Digital Converter (ADC) for Weigh Scales

DESCRIPTION

Based on Avia Semiconductor’s patented

technology, HX711 is a precision 24-bit analog-

to-digital converter (ADC) designed for weigh

scales and industrial control applications to

interface directly with a bridge sensor.

The input multiplexer selects either Channel A

or B differential input to the low-noise

programmable gain amplifier (PGA). Channel A

can be programmed with a gain of 128 or 64,

corresponding to a full-scale differential input

voltage of ±20mV or ±40mV respectively, when

a 5V supply is connected to AVDD analog power

supply pin. Channel B has a fixed gain of 32. On-

chip power supply regulator eliminates the need

for an external supply regulator to provide analog

power for the ADC and the sensor. Clock input is

flexible. It can be from an external clock source, a

crystal, or the on-chip oscillator that does not

require any external component. On-chip power-

on-reset circuitry simplifies digital interface

initialization.

There is no programming needed for the

internal registers. All controls to the HX711 are

through the pins.

FEATURES

• Two selectable differential input channels

• On-chip active low noise PGA with selectable gain

of 32, 64 and 128

• On-chip power supply regulator for load-cell and

ADC analog power supply

• On-chip oscillator requiring no external

component with optional external crystal

• On-chip power-on-reset

• Simple digital control and serial interface:

pin-driven controls, no programming needed

• Selectable 10SPS or 80SPS output data rate

• Simultaneous 50 and 60Hz supply rejection

• Current consumption including on-chip analog

power supply regulator:

normal operation < 1.5mA, power down < 1uA

• Operation supply voltage range: 2.6 ~ 5.5V

• Operation temperature range: -40 ~ +85℃

• 16 pin SOP-16 package

APPLICATIONS

• Weigh Scales

• Industrial Process Control

2.7~5.5V

VBG

PGA

Gain = 32, 64, 128

24-bit Σ∆

ADC

Input

MUX

Digital

Interface

Analog Supply Regulator

Internal

Oscillator

Bandgap Reference

HX711

XI XO

DOUT

PD_SCK

RATE

BASE VSUP DVDD

INB-

INB+

INA-

INA+

To/From

MCU

AVDD

AGND

Load cell

Fig. 1 Typical weigh scale application block diagram

VFB

0.1uF

10uF

S8550

AVDD

SUP

Summary of content (9 pages)

PAGE 1
HX711 24-Bit Analog-to-Digital Converter (ADC) for Weigh Scales DESCRIPTION FEATURES Based on Avia Semiconductor’s patented technology, HX711 is a precision 24-bit analogto-digital converter (ADC) designed for weigh scales and industrial control applications to interface directly with a bridge sensor. The input multiplexer selects either Channel A or B differential input to the low-noise programmable gain amplifier (PGA).
PAGE 2
HX711 Pin Description Regulator Power VSUP 1 16 DVDD Digital Power Regulator Control Output BASE 2 15 RATE Output Data Rate Control Input Analog Power AVDD 3 14 XI Crystal I/O and External Clock Input Crystal I/O Serial Data Output Regulator Control Input VFB 4 13 XO Analog Ground AGND 5 12 DOUT Reference Bypass VBG 6 11 PD_SCK Power Down and Serial Clock Input Ch. A Negative Input INNA 7 10 INPB Ch. B Positive Input Ch. A Positive Input INPA 8 9 INNB Ch.
PAGE 3
HX711 KEY ELECTRICAL CHARACTERISTICS Parameter Full scale differential input range Notes TYP MAX ±0.5(AVDD/GAIN) V(inp)-V(inn) Common mode input Output data rate MIN AGND+1.2 Internal Oscillator, RATE = 0 Internal Oscillator, RATE = DVDD Crystal or external clock, RATE = 0 Crystal or external clock, RATE = DVDD UNIT V AVDD-1.3 10 V Hz 80 fclk/1,105,920 fclk/138,240 Output data coding 2’s complement Output settling time (1) RATE = 0 400 RATE = DVDD 50 Gain = 128 0.2 Gain = 64 0.
PAGE 4
HX711 Analog Inputs Channel A differential input is designed to interface directly with a bridge sensor’s differential output. It can be programmed with a gain of 128 or 64. The large gains are needed to accommodate the small output signal from the sensor. When 5V supply is used at the AVDD pin, these gains correspond to a full-scale differential input voltage of ±20mV or ±40mV respectively. Channel B differential input has a fixed gain of 32.
PAGE 5
HX711 Next Output Data Current Output Data One conversion period MSB DOUT LSB T2 T3 T1 PD_SCK 1 2 3 PD_SCK 1 2 PD_SCK 1 2 Next Conversion：CH.A, Gain:128 4 24 25 3 4 24 25 26 3 4 24 25 26 T4 Next Conversion：CH.B, Gain:32 27 Next Conversion：CH.B, Gain:64 Fig.2 Data output, input and gain selection timing and control Symbol Note MIN T1 DOUT falling edge to PD_SCK rising edge 0.1 T2 PD_SCK rising edge to DOUT data ready T3 PD_SCK high time 0.
PAGE 6
HX711 Reference PCB Board (Single Layer) Fig.4 Reference PCB board schematic Fig.
PAGE 7
HX711 Reference Driver (Assembly) /*------------------------------------------------------------------Call from ASM: LCALL ReaAD Call from C: extern unsigned long ReadAD(void); . . unsigned long data; data=ReadAD(); . . ----------------------------------------------------------------------*/ PUBLIC ReadAD HX711ROM segment code rseg HX711ROM sbit ADDO = P1.5; sbit ADSK = P0.
PAGE 8
HX711 Reference Driver（C） //------------------------------------------------------------------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); } AVIA SEMICONDUCTOR 8
PAGE 9
HX711 Package Dimensions 9.90 10.10 9.70 6.00 6.20 5.80 3.90 4.10 3.70 1.27 0.48 0.39 1.60 1.