Read Vcc pulls 200uA with LowPower sleep about arduino_vcc HOT 3 OPEN

long readVccFixedLowPower() {
  long result;
  // Read 1.1V reference against AVcc
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
  delay(1); // Wait for Vref to settle
  ADCSRA |= _BV(ADSC); // Convert
  while (bit_is_set(ADCSRA,ADSC));
  result = ADCL;
  result |= ADCH<<8;
  result = ( 1023L * 1100L) / result; // Back-calculate AVcc in mV. 1100 is volt on vRef.
  //to fix lowpower drain, ADMUX is changed again.
  ADMUX = _BV(REFS1); //fixes readVcc current drain in lowPower
  Serial.print("Vcc = " );
  Serial.println(result); 
  return result;
}