TLC976C

10-BIT, 20 MSPS, AREA CCD SIGNAL PROCESSOR

SLAS193 – OCTOBER 1998

13

POST OFFICE BOX 655303

PRINCIPLES OF OPERATION

ADC internal calibration

start-up calibration at power up

After power is turned on, the start-up calibration starts under the following conditions:

1.

The voltage between VRT and VRB is over 1 V when the voltage between AVDD and AVSS is over 2.5 V.

2.

The voltage between DVDD and DVSS is over 2.5 V.

3.

The RESET terminal (pin 26) is high.

4.

The AD-STBY terminal (pin 31) is low.

The calibration sequence starts after condition 2 is met (see Figure 7). The following equation calculates the

time required for the start-up calibration after the above conditions are met.

Start-up calibration time = main clock pulse period

× 16 × 16384

For example, if the main clock frequency is 15 MHz, the time required for startup calibration is 17.5 ms.

5 V

2.5 V

1 V

Reset = HIGH, AD-STBY = LOW

AVDD

VRT

DVDD

VRB

CALIBRATION START

Figure 7. Start-Up Calibration