ZL9101M_1104 Datasheet, PDF (13/17 Pages) Intersil Corporation – Digital DC/DC PMBus 12A Module

ZL9101M
calibrating out the physical parasitic mismatches due to power
train components and PCB layout.
Upon system start-up, the module with the lowest member position as
selected in ISHARE_CONFIG is defined as the reference module. The
remaining modules are members. The reference module broadcasts its
current over the DDC bus. The members use the reference current
information to trim their voltages (V_MEMBER) to balance the current
loading of each module in the system.
V_{R E FER EN C E}
-R
V_MEMBER
-R
I_MEMBER
I_OUT
I _{R EFER EN C E}
FIGURE 12. ACTIVE CURRENT SHARING
Figure 12 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:
( ) V_MEMBER
= V_OUT
+ R×
I − I _REFERENCE
MEMBER
(EQ. 2)
where R is the value of the droop resistance.
The ISHARE_CONFIG command is used to configure the module
for active current sharing. The default setting is a stand-alone
non-current sharing module. 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 module
fails, the remaining members will continue to operate and
attempt to maintain regulation. Of the remaining modules, the
module with the lowest member position will become the
reference. If fault spreading is enabled, the current share rail
failure is not broadcast until the entire current share rail fails.
The phase offset of (multi-phase) current sharing modules is
automatically set to a value between 0° and 337.5° in 22.5°
increments as follows:
Phase Offset= SMBus Address[4:0] – Current
Share Position^∗22.5°
(EQ. 3)
Please refer to Application Note AN2034 for additional details on
current sharing.
Phase Adding/Dropping
The ZL9101M 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 ZL9101M offers the ability to add and drop phases using a
PMBus command in response to an observed load current
change. All phases in a current share rail are considered active
prior to the current sharing rail ramp to power-good.
Any member of the current sharing rail can be dropped. If the
reference module is dropped, the remaining active module 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.
Monitoring via I²C/SMBus
A system controller can monitor a wide variety of different
ZL9101M system parameters through the I²C/SMBus interface.
The module can monitor for any number of power conversion
parameters including but not limited to the following:
• Input voltage/Output voltage
• Output current
• Internal temperature
• Switching frequency
• Duty cycle
Please refer to Application Note AN2033 for details on how to
monitor specific parameters via the I²C/SMBus interface.
Snapshot Parameter Capture
The ZL9101M offers a special feature that enables the user to
capture parametric data during normal operation or following a
fault. The Snapshot functionality is enabled by setting bit 1 of
MISC_CONFIG to 1.
See AN2033 for details on using SnapShot in addition to the
parameters supported. The Snapshot feature enables the user to
read parameters via a block read transfer through the SMBus.
This can be done during normal operation, although it should be
noted that reading the 22 bytes will occupy the SMBus for some
time.
The SNAPSHOT_CONTROL command enables the user to store
the snapshot parameters to Flash memory in response to a
pending fault as well as to read the stored data from Flash
memory after a fault has occurred. Table 3 describes the usage
of this command. Automatic writes to Flash memory following a
fault are triggered when any fault threshold level is exceeded,
provided that the specific fault’s response is to shut down
(writing to Flash memory is not allowed if the device is configured
to re-try following the specific fault condition). It should also be
noted that the module’s V_DD voltage must be maintained during
the time when the controller is writing the data to Flash memory;
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FN7669.2
April 8, 2011