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LTC2644-L12 Rising Edge to DAC Update Delay

Question asked by ste on Mar 7, 2018
Latest reply on Mar 12, 2018 by Clarence.Mayott

Dear Sir,

I'm using the LTC2644-12 for motor control applications.


My PWM is set to 6kHz hence Tpwm=1/6000.


I need some clarification about parameter t4 (device datasheet 2644fa), because  about t4 INA/INB Rising Edge to DAC Update Delay we can read 3.2 us TYP, this should be the time needed to perform the output voltage update after receiving a full PWM cycle and this one is unique parameter no matter about the bit resolution.


Into the first page of the datasheet, Description paragraph, I can read:


"The DAC outputs update and settle to 12-bit accuracy within 8μs typically..."


now I'm not sure about what should be the correct value for t4 parameter, is 3.2 us typ valid for all resolution, I've to consider 8 us for the 12 bit, there are other value related to the resolution? What is the correct value to take in account?


I need to know this parameter because I've to accurately calculate my updating loop into the microcontroller, final updating time will be:


t_loop-up + t_pwm + T4 = t_loop-up + (1/6000) + T4


Thanks in advance!