User Manual
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V 1.0
2021-08-25
XDPP1100 technical reference manual
Digital power controller
Current sharing (ISHARE)
10
Current sharing (I
SHARE
)
This chapter discusses the current sharing feature in more detail as well as the relevant register settings related
to current sensing.
In order to increase power delivery to the load, multiple power supplies may be connected in parallel to drive a
common output voltage. However, equal current sharing between the supplies is not automatically
guaranteed. For example, if one supply has a slightly higher V
OUT
it tends to deliver more power to the load than
a lower-voltage supply. In extreme cases, the higher-voltage supply may even source current into the lower-
voltage supply leading to reduced system efficiency. Other detrimental effects of unequal current sharing
include reduced total power delivery and early triggering of overcurrent or overtemperature protection.
Current sharing can be performed either actively or passively, and the XDPP1100 supports both methods to
balance currents between supplies. Passive current sharing uses the droop resistance load-line as described in
. No additional external components or connections are required, and each supply is programmed
with a non-zero droop resistance. A supply with a higher no-load output voltage tends to drive a higher portion
of the output current, leading to a higher V
OUT
droop than a lower output voltage supply. The current in the
parallel units reaches a balance when the output voltage in each unit droops to the same voltage.
Active current sharing requires a connection between the supplies in order to share average current
implementation. The XDPP1100 implementation also requires one external resistor per supply in order to
compute the average system current. The remaining subsections in this chapter will discuss the XDPP1100
active current sharing implementation.
10.1
Current sharing circuit
For active current sharing, the XDPP1100 IMON pin is used to share the current information between power
supplies. An example system with two XDPP1100-based power supplies connected in parallel is shown in
Figure 85
Active current sharing example with two units in parallel with simultaneous module start-
up
V
OUT
+
V
OUT
-
Ishare
IMON
Unit 1
V
IN
+
V
IN
-
RC
V
OUT
+
V
OUT
-
Ishare
IMON
Unit 2
V
IN
+
V
IN
-
RC
R
ishare
R
ishare
I
OUT1
I
OUT2
I
OUT
Load
k*I
OUT1
k*I
OUT2
XDPP1100
XDPP1100
