zl2006 Intersil Corporation, zl2006 Datasheet - Page 38

• Manufacturer Part Number: zl2006
• Description: Adaptive Digital Dc-dc Controller With Drivers And Current Sharing
• Manufacturer: Intersil Corporation

Droop resistance is used to add artificial resistance in
the output voltage path to control the slope of the load
line curve, calibrating out the physical parasitic
mismatches due to power train components and PCB
layout.
Upon system start-up, the device with the lowest
member position as selected in ISHARE_CONFIG is
defined as the reference device. The remaining devices
are members. The reference device broadcasts its
current over the DDC bus. The members use the
reference current information to trim their voltages
(V
device in the system.
Figure 24 shows that, for load lines with identical
slopes, the member voltage is increased towards the
reference voltage which closes the gap between the
inductor currents.
The relation between reference and member current
and voltage is given by the following equation:
where R is the value of the droop resistance.
The ISHARE_CONFIG command is used to configure
the device for active current sharing. The default
setting is a stand-alone non-current sharing device. A
current sharing rail can be part of a system sequencing
group.
For fault configuration, the current share rail is
configured in a quasi-redundant mode. In this mode,
when a member device fails, the remaining members
will continue to operate and attempt to maintain
regulation. Of the remaining devices, the device with
the lowest member position will become the reference.
If fault spreading is enabled, the current share rail
MEMBER
V
MEMBER
) to balance the current loading of each
Figure 24. Active Current Sharing
=
V
OUT
38
+
R
×
(
I
REFERENCE
−
I
MEMBER
)
ZL2006
failure is not broadcast until the entire current share rail
fails.
Up to eight (8) devices can be configured in a given
current sharing rail.
6.16 Phase Adding/Dropping
The ZL2006 allows multiple power converters to be
connected in parallel to supply higher load currents
than can be addressed using a single-phase design. In
doing so, the power converter is optimized at a load
current range that requires all phases to be operational.
During periods of light loading, it may be beneficial to
disable one or more phases in order to eliminate the
current drain and switching losses associated with
those phases, resulting in higher efficiency.
The ZL2006 offers the ability to add and drop phases
using a simple command in response to an observed
load
continuously optimize overall efficiency across a wide
load range. All phases in a current share rail are
considered active prior to the current sharing rail ramp
to power-good.
Phases can be dropped after power-good is reached.
Any member of the current sharing rail can be
dropped. If the reference device is dropped, the
remaining active device with the lowest member
position will become the new reference.
Additionally, any change to the number of members of
a current sharing rail will precipitate autonomous phase
distribution within the rail where all active phases
realign their phase position based on their order within
the number of active members.
If the members of a current sharing rail are forced to
shut down due to an observed fault, all members of the
rail will attempt to re-start simultaneously after the
fault has cleared.
current
change,
enabling
December 15, 2010
the
system
FN6850.1
to