User Manual
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V 1.0
2021-08-25
XDPP1100 technical reference manual
Digital power controller
Voltage sense
The terms utilized in the equations are defined as follows:
•
Vin_init is the initial input voltage (i.e., 48 V for a 36 V to 72 V system), and it must be greater than the PMBus
command VIN_ON setting in order for start-up to occur.
•
MFR_VRECT_SCALE is a PMBus command defining the resistor divider ratio between V
RECT
and the VRSEN
input pin.
•
MFR_TRANSFORMER_SCALE is a PMBus command defining the transformer turns ratio.
shows the start-up response of the V
RECT
measurement.
Figure 15
V
RECT
sense start-up
2.3.2.7
Same cycle response
As a default feature, the sensed rectified voltage is sampled once per cycle at the PWM falling edge. Thus, the
current V
RECT
value does not contribute to the PWM turn-off via FF
function. An alternate “same cycle” mode is
available and user programmable by:
•
Enabling the register
vrs_same_cycle_en
•
Defining the time before the live samples appear on the V
RECT
output (register
vrs_meas_start_thr
) after
entering the tracking window
The same cycle mode is illustrated in
, where the bottom two waveforms compare the V
RECT
output
with and without same cycle mode. For the best input voltage transient response, it is recommended to enable
the same cycle mode.
PWM
VRSEN
V
IN
Hold Time
Tracking
Window
V
IN
Telemetry
vin_init *
* vin_init is a topology dependent function of register vrs_voltage_init and PMBus commands
MFR_VRECT_SCALE and MFR_TRANSFORMER_SCALE
