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TPS51200 VREF range

Nikhil Tiwari
Intellectual 575 points
Other Parts Discussed in Thread: TPS51200

Hi,

We are planning to use TPS51200 to generate the VTT as well as VREF for DDR3. DDR3 datasheet it is specified that the operating range for reference voltages are 0.49VDD (0.735V) to 0.51VDD (0.765V). 

TPS51200 REFOUT pin follows the REFIN voltage by +15mV.

The REFIN is generated using the 10KΩ resistor divider circuit. These resistors are 1% tolerant but the temperature coefficient is 100ppm/0C. So at extreme temperatures (-40 and 85) these resistor values can vary from 10060Ω to 9940Ω. 

Based on these variations in resistor values the worst case variation in REFIN can be 0.7455V o 0.7545V. Adding the +15mV variation in these values the output VREF (REFOUT) can vary from 0.7305V to 0.7695V which goes out of our required range for DDR3.

Does the +15mV variation of device includes the resistor variations? If not then what is suggested as it can cause an issue at higher temperatures.

thanks & regards,

Nikhil