Datasheet DS4303 (Analog Devices) - 7

Electronically Programmable Voltage Reference DS4303 AUTOMATED TEST EQUIPMENT DEVICE UNDER TEST (DUT)
DS4303 2.4V TO 3.6V VCC EEPROM
STEP 1:
DIGITALLY SET REFERENCE CONTROLLED VIN VOLTAGE VOLTAGE SOURCE VOLTAGE ADJ SAMPLE AND INFINITE
STEP 2:
DIGITAL PIN DRIVER HOLD TOGGLE ADJ GND VOUT BED-OF-NAILS TEST CIRCUITRY ACCESS REQUIRING
STEP 3:
VOLTAGE DETERMINE IF DIGITALLY PARAMETER MEASURED ADJUSTMENT THE REFERENCE CONTROLLED DURING CALIBRATION VOLTAGE NEEDS MEASUREMENT ADJUSTMENT Figure 2. Application Circuit During the VOUT self-adjust period, the DS4303 inter- circuit. VOUT can be readjusted at any time by following nally adjusts the onboard DAC until VOUT matches VIN. the same procedure. The closed-loop nature of the After VOUT has stabilized to within the tracking accura- adjustment process removes all the system inaccura- cy, VOUTTA, of VIN, it will be automatically stored in cies such as resistor tolerances, amplifier offsets, gain EEPROM. The storage period lasts for the duration of mismatches, and even the inaccuracies in the automat- the EEPROM write time, tW. After the first adjustment ed equipment that provides the reference voltage. procedure has completed, VOUT can be measured, and if necessary V
Typical Operating Circuit
IN can be readjusted and the entire adjustment procedure can be repeated to fine-tune The typical operating circuit shows an example of how V the DS4303 can replace most existing calibration solu- OUT within the VOUTQ range. tions. Many power supplies use a shunt voltage refer- Following each self-adjust procedure, VOUT is saved ence to provide the internal reference voltage, and indefinitely, even if the DS4303 is power cycled. fine-tune adjustments are often made with hand-select-
Automated Programming Procedure
ed discrete resistors. The DS4303 replaces this cum- Figure 2 details an example of how the DS4303 can be bersome arrangement with a solution that is capable of adjusted in an application. During factory alignment, a being adjusted by automated techniques. An additional three/four-node bed-of-nails is used to: (1) provide the benefit of the DS4303 is the ability to provide a much adjustment voltage through the V lower voltage (down to 300mV) than is possible with IN pin, (2) control the ADJ input, and (3) sense the needed feedback para- shunt voltage references. Another benefit of the meter. During manufacture, an automated test proce- DS4303 is the ability to be adjusted after the unit has dure adjusts V been fully assembled and tested, resulting in a much OUT, by changing VIN, until the feedback parameter is optimized. After the bed-of-nails operation more flexible manufacturing arrangement, lower inven- is complete, both the V tory costs, and a quicker time-to-market. IN and ADJ inputs are left open
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