User Manual
25 of 562
V 1.0
2021-08-25
XDPP1100 technical reference manual
Digital power controller
Voltage sense
Figure 14
V
RECT
sense transient
2.3.2.6
V
RECT
start-up programming
At start-up, prior to the first PWM pulse, there is no V
RECT
pulse on the secondary to be measured. Therefore, in
order to enable start-up, user-programmable initial voltage (register
vrs_voltage_init
) is provided for:
•
FF
•
Telemetry
•
Fault conditions
Without pre-bias (i.e., output ramps from 0 V), the initial PWM pulses are narrower than the tracking start timer
threshold. During this time, the V
RECT
tracking ADC continues to output the initial voltage set by the user. Once
the PWM pulses obtain a width greater than the tracking start timer threshold, the ADC begins to track toward
the actual V
RECT
voltage.
The initial voltage to be set in the register
vrs_voltage_init
depends on the topology. For HB it can be
calculated as in Equation (2.2).
𝑣𝑟𝑠_𝑣𝑜𝑙𝑡𝑎𝑔𝑒_𝑖𝑛𝑖𝑡 = (
𝑣𝑖𝑛_𝑖𝑛𝑖𝑡(𝑉)
0.04𝑉
) ∗ 𝑀𝐹𝑅_𝑉𝑅𝐸𝐶𝑇_𝑆𝐶𝐴𝐿𝐸 ∗ 𝑀𝐹𝑅_𝑇𝑅𝐴𝑁𝑆𝐹𝑂𝑅𝑀𝐸𝑅_𝑆𝐶𝐴𝐿𝐸
(2.2)
For FB and ACF as in Equation (2.3)
𝑣𝑟𝑠_𝑣𝑜𝑙𝑡𝑎𝑔𝑒_𝑖𝑛𝑖𝑡 = (
𝑣𝑖𝑛_𝑖𝑛𝑖𝑡(𝑉)
0.02𝑉
) ∗ 𝑀𝐹𝑅_𝑉𝑅𝐸𝐶𝑇_𝑆𝐶𝐴𝐿𝐸 ∗ 𝑀𝐹𝑅_𝑇𝑅𝐴𝑁𝑆𝐹𝑂𝑅𝑀𝐸𝑅_𝑆𝐶𝐴𝐿𝐸
(2.3)
PWM
VRSEN
Tracking ADC
DAC Output
Hold Time
Tracking
Window
V
IN
