This presentation will now take a closer look at the successive approximation steps in determining the value of the ISENSOR source. The SAR will set the current source to mid-scale and drive the ramp until the timeout period expires as governed by the reference capacitor charge time. Mid-scale for the 16-bit current source is 0x8000. At this point the voltages are compared.  If the sensor capacitor has charged to a value that is greater than the reference, there was too much current and the MSB value is then set as a zero. Conversely, if the current did not reach the threshold, there was not enough current and the MSB is then set to a one. Since the previous bit was set low the next weighted bit is set to a value lower, half of the setting or 0x4000. The charge cycle is started again and the voltages are once again compared. In the example shown it can be seen that with this new value the voltage did not reach the threshold point, therefore it is necessary to supply more current to the sensor capacitor. This bit is then set as a one and the next value is again the halfway point to the mid-scale voltage or 0x6000. This process continues to the last bit, at which time the ramp rates of the two capacitors are equal.