Datasheet DS4305 (Analog Devices) - 6

Electronically Programmable Voltage Reference Pin Description Detailed Description
The DS4305 provides a precise, NV output voltage,
PIN NAME FUNCTION
VOUT, making it an ideal solution for factory calibration 1 ADJ Adjust Control Input of embedded systems. The DS4305 output voltage can 2 GND Ground be adjusted over almost the entire operating supply range of the device, and it can be precisely set to with- 3 V
DS4305
IN Sample Voltage Input in ±1.5mV. A graphical description of the DS4305 is 4 VOUT Voltage Output provided in the block diagram. 5 VCC Power-Supply Voltage During factory calibration, a simple adjustment proce- dure must be followed. This entire procedure includes setting VIN, toggling ADJ, waiting as VOUT self-adjusts,
Block Diagram
and waiting for the completion of the EEPROM storage cycle (see the timing diagram in Figure 1). At the start of calibration, a voltage must be placed on VIN. This voltage needs to be completely stable before the VCC adjustment procedure begins, and it must remain sta- DS4305 ble throughout the entire adjustment procedure. The RPU DS4305 starts its self-adjust procedure when the ADJ pin is pulled low and held low for at least t ADJ ADJ, after ADC VOUT which it can be released at any time. Once ADJ has 12-BIT AND DAC been released, it should not be toggled again for the CONTROL remainder of the adjustment procedure. After the falling VIN edge on ADJ and the wait time, tADJ, the VOUT self- VCC RPD VREF adjust period begins. The length of the VOUT self-adjust VCC period can be determined using the formula EEPROM GND ∆V x tST, where ∆V is | VOUT OLD - VOUT NEW |. V ∆V OUT ∆V OUT OUT ∆V ∆ OUT x tST VOUT x tST VIN tW tW ADJ tADJ tADJ tADJ FIRST PROGRAMMING CYCLE ADDITIONAL PROGRAMMING CYCLES (IF REQUIRED) Figure 1. Timing Diagram
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