TIPD125: TIPD125 (DAC8560) No Negative Voltage

I'm working with a TIPD125 evaluation board populated with all recommended components from the application note (SLAU525).

I've hooked the board up to a Teensy 3.6 for SPI comms and have correctly connected a +/-15V supply to VCC/VSS and the VDD/GND is supplied from the Teensy itself. I believe this is correct.

I am able to write successfully to the DAC and I am able to generate a voltage - however, the voltage is only between 0 and 10V, not +/-10 as per the app note.

The code I'm using is as follows and just generates a simple ramp up:

#include <SPI.h>

#define DAC_SYNC_PIN 0

SPISettings settingsA(1000000, MSBFIRST, SPI_MODE2); 

void setup() {
  // put your setup code here, to run once:

  // Initialize the SPI bus
  SPI.begin();
  // Set the SYNC pin
  pinMode(DAC_SYNC_PIN, OUTPUT);
}

static void startSync() {
  digitalWrite(DAC_SYNC_PIN, LOW);
}

static void endSync() {
  digitalWrite(DAC_SYNC_PIN, HIGH);
}

static void writeValue(uint16_t val) {
  uint8_t msb = ((val & 0xFF00) >> 8);
  uint8_t lsb = ((val & 0x00FF) >> 8);

  SPI.beginTransaction(settingsA);
  startSync();
  SPI.transfer(0x00);
  SPI.transfer(msb);
  SPI.transfer(lsb);
  endSync();
  SPI.endTransaction();
}

static uint16_t i = 0;
static bool up = true;

void loop() {
  // put your main code here, to run repeatedly:
  i += 10;

  if (i > 0xFFFF)
    i = 0;
  
  writeValue(i);
}