User Manual
287 of 562
V 1.0
2021-08-25
XDPP1100 technical reference manual
Digital power controller
Current sharing (ISHARE)
supply current is given in amps. As an example, if an individual supply can handle 50 A, then the
ishr_scale
value is as given in Equation (10.4).
𝑖𝑠ℎ𝑟_𝑠𝑐𝑎𝑙𝑒 = 𝑖𝑛𝑡𝑒𝑔𝑒𝑟 (16 ∗
32
𝐼_𝑠𝑢𝑝𝑝𝑙𝑦_𝑚𝑎𝑥
)
(10.3)
𝑖𝑛𝑡𝑒𝑔𝑒𝑟 (16 ∗
32
50
) = 10
(10.4)
The scaled current is then offset to allow the DAC to also represent negative currents using the bottom half of
its range. The DAC is a 6-bit current DAC with four additional LSBs used for LSB modulation. Thus, it is possible
to achieve approximately 10 bits of voltage resolution across the R
ishare
resistor when a filter capacitor is
connected between the IMON pin and ground.
The TSADC measures the voltage at the IMON pin and converts it to a digital representation. An error current is
generated from the difference between:
•
The measured IMON voltage (representing the target current I
OUT
/N)
•
The scaled current from the telemetry block
A programmable deadzone is provided through register
ishare_dead_zone
, allowing the current error to be
zeroed out within a zone of current around 0 A. Subsequent to the deadzone, the error current proceeds to a PI
compensation filter (described in
). The output of this PI filter is in the format of an adjustment
term to the target voltage. Both positive and negative voltage adjustments are allowed using the following
registers:
•
ishare_clamp_pos
•
ishare_clamp_neg
The registers can be used to limit the magnitude of the target voltage adjustment or to limit the adjustment to
a single direction only. In order to prevent adjustment in a given direction, the associated clamp parameter
needs to be set to 0.
A current sharing fault is declared under the following conditions:
•
If the PI filter output exceeds the register value
ishare_clamp_pos
and the output of the deadzone function
is greater than 0
•
If the PI filter output is below the register value
ishare_clamp_neg
and the output of the deadzone function
is less than 0
10.2
Current sharing PI filter
The error current is processed by the PI filter, which consists of:
•
A proportional term operating on the instantaneous current error
•
An integral term operating on the accumulated current error
The integral term sets the low-frequency gain and the proportional term sets the high-frequency gain of the
filter. The magnitude response of the filter is defined by Equations (10.5) to (10.8).
|𝐻
𝑃𝐼
(𝑓)| = √𝐾
𝑃
2
+ (
𝐾
𝐼
2𝜋∙𝑇
𝑆𝐴𝑀𝑃𝐿𝐸
∙𝑓
)
2
(10.5)
𝐾
𝑃
= (8 + 𝑖𝑠ℎ𝑟_𝑘𝑝[2: 0]) ∙ 2
(𝑖𝑠ℎ𝑟_𝑘𝑝[5:3]−10)
(10.6)
𝐾
𝐼
= (8 + 𝑖𝑠ℎ𝑟_𝑘𝑖[2: 0]) ∙ 2
(𝑖𝑠ℎ𝑟_𝑘𝑖[5:3]−12)
(10.7)
𝑇
𝑆𝐴𝑀𝑃𝐿𝐸
=
1
𝐹
𝑆𝑊𝐼𝑇𝐶𝐻
(10.8)
