I am currently using a DRV8303 to drive a BLDC motor. There is an issue with current sensing.
Without any motor attached to my board and a motor voltage (PVDD) connected, the current sense output (SO1 and SO2) is correct.
I have checked that SN1 and SP1 as well as SN2 and SP2 are at exactly 0 V, which is correct since there is no current flowing through the shunt resistor. Reference input REF is at exactly 3.3 V. The output of the SO1 and SO2 pin is 1.65V, which is normal.
To test if the amplifier is functioning, I remove the shunt resistor, which is connected to the SN1 and SP1 pins, and manually apply a voltage(0.100V) to the SN1 pin, which supposedly will be amplified, and the voltage on the SO1(output) pin will drop to 0.65V (according to the formula [1.65-(0.1*10)] as I set the gain of the C.S.A. to 10V). However, the voltage on the SO1 pin remains to be 1.65V. The output of the C.S.A is unresponsive to the input.
Here is my schematic and circuit:
BRD: https://drive.google.com/file/d/1lv5I7GT6esK-80-wN8fSaVhWlB1ejIwC/view?usp=sharing
SCH: https://drive.google.com/file/d/1lvBKcgRM2TCG_ksn0xLjSbLgVWraZkdn/view?usp=sharing
Here is my code:
#include <SPI.h>
#define INHA PA8
#define INLA PA9
#define SO1 PB1
#define INHB PA10
#define INLB PB6
#define SO2 PB0
#define INHC PB7
#define INLC PB8
#define LED PC13
#define EN_GATE PB12
#define NOCTW PB14
#define NFAULT PB13
#define chipSelectPin PA4
word data;
void changeSPI3PWM()
{
digitalWrite(chipSelectPin, LOW); // manually take CSN low for SPI_1 transmission
data = SPI.transfer16(0b0001000000111000); //0 0010 00000111000
digitalWrite(chipSelectPin, HIGH);
}
void changeCurrentSense() {
digitalWrite(chipSelectPin, LOW);
data = SPI.transfer16(0b000110000000000); //0 0011 0000000000
digitalWrite(chipSelectPin, HIGH);
}
void setup() {
SPI.begin();
SPI.setBitOrder(MSBFIRST);
SPI.setDataMode(SPI_MODE1);
SPI.setClockDivider(SPI_CLOCK_DIV16);
pinMode(chipSelectPin, OUTPUT);
Serial.begin(115200);
pinMode(INHA, OUTPUT);
pinMode(INLA, INPUT);
pinMode(SO1, INPUT);
pinMode(INHB, OUTPUT);
pinMode(INLB, INPUT);
pinMode(SO2, INPUT);
pinMode(INHC, OUTPUT);
pinMode(INLC, INPUT);
pinMode(EN_GATE, OUTPUT);
pinMode(PB4, OUTPUT);
pinMode(NOCTW, INPUT);
pinMode(NFAULT, INPUT);
pinMode(LED, OUTPUT);
digitalWrite(PB4, LOW); //PB4 is the DC_CAL PIN
digitalWrite(EN_GATE, HIGH);
changeSPI3PWM();
changeCurrentSense();
}
void loop() {
digitalWrite(INHB, HIGH);
digitalWrite(INHA, HIGH);
digitalWrite(INHC, HIGH);
if (digitalRead(NFAULT) == LOW) {
Serial.println("NFault low");
}
if (digitalRead(NOCTW) == LOW) {
Serial.println("NOCTW low");
}
Serial.print(Current_Calculation(analogRead(SO1) / 4096. *3.3), 10);
Serial.print(" ");
Serial.println(Current_Calculation(analogRead(SO2) / 4096. *3.3), 10);
}
double Current_Calculation(double RawVolt) {
const double K = 2. ;
const double G = 80.;
const double VREF = 3.3;
return (VREF - (K * RawVolt)) / (G * K); //general solve
}
Do you have an explanation of what might be the most likely reason for this error?
Sincerely,
Dennis Chang
