If I disable the fast servo mode (work at slow servo mode), the DAC is ramped one lsb every Ts_vdacp period according to the datasheet.
I want to know if LTC2977 still need to monitor the ADC input during every ramped lsb? For example, the initial MFG_DAC_LTC is n, DAC ramp it to n+1, delay Ts_vdacp plus "tUPDATE_ADC", then DAC ramp it to n+2.
Or DAC successively ramp it, DAC ramp it to n+1, delay Ts_vdacp, DAC ramp it to n+2, delay Ts_vdacp, DAC ramp it to n+3 .... And the digital servo loop is disabled during DAC ramping.
The ADC provides a new conversion result to the servo at the rate of tUPDATE_ADC. In slow servo mode, the servo block looks at this result and increments/decrements the DAC 1 LSB toward the target (VOUT_COMMAND). In this mode, the servo updates at the update rate of the ADC (~90ms). In fast servo mode, the servo block does not wait for the updated ADC result - it moves the DAC 1 LSB every 500us (tS_VDACP) until the target is reached.
But according to the datasheet it moves the DAC 1 LSB every 500us (tS_VDACP) until the target is reached in slow servo mode, could you help to double check it, thanks.
When the 'fast_servo_off' configuration bit is cleared (logic 0), the channel will be in fast servo mode. When the bit is set (logic 1), the channel will be in slow mode. If the channel is in slow mode, the tS_VDACP 500us per DAC step does not apply to any changes in the output state, even at channel startup. If the channel is in fast mode, tS_VDACP 500us per DAC step applies, but only applies upon channel startup (when it first reaches the target), a change in VOUT_COMMAND value, or a Margin command being issued. I hope this clarifies the servo/DAC operation.