ZL2004 datasheet(36/42 Pages) RENESAS

36 / 42 page

ZL2004

FN6846 Rev. 3.00

Page 36 of 42

February 15, 2011

Figure 20 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:





MEMBER

REFERENCE

OUT

member









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. The device 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.

Up to eight (8) devices can be configured in a given

current sharing rail.

6.16 Phase Adding/Dropping

The ZL2004 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 ZL2004 offers the ability to add and drop phases

using a simple command in response to an observed

load

current

change,

enabling

the

system

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.

6.17 Monitoring via I2C/SMBus

A system controller can monitor a wide variety of

different ZL2004 system parameters through the

2C/SMBus interface. The device can monitor for fault

conditions by monitoring the SALRT pin, which will

be asserted when any number of pre-configured fault

conditions occur.

Figure 20. Active Current Sharing

-R

VREFERENCE

VMEMBER

IMEMBER

IREFERENCE

IOUT

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