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Power Management Overview and PMBus Interface (Applicable Models)

A wide range of parameters can be read and configured by the system/host by

using PMBus™ digital communications.

Each module is provided pre-configured for a wide range operation. Refer to the

PMBus™ Interface section for details.

SMBAERT# Hardware Signal (Applicable Models)

SMBALERT# signal offers an alternate method for system/host notification that a

fault or Warning has been detected (mirrors the STATUS_X fault/warn register bits)

within the module and is useful in applications requiring real time fault notifica-

tion independent or in addition to reading PMBus™ STATUS_X register fault bits

which may not be read by system/host frequently enough to detect that a fault/

warning bit flag was set.

Internally driven low <0.4Vdc indicates a Vout, Iout, Vin, Temperature, or Power

Good fault/warning has been detected and remains low until the fault/warning

stimulus has been removed and the system/host clears the individual bit flag or

issues “CLEAR_FAULTS” command.

Drive high, >2.4Vdc to indicate no fault conditions within power module are

detected.

Soft-start Power Up

The default rise time of the ramp up is 30ms. When starting by applying input volt-

age the control circuit boot-up time adds an additional 10ms delay. The soft-start

power up of the module can be reconfigured using the PMBus interface.

Output Over Voltage Protection (OVP)

Both OVP limit and response can be configured via PMBus command (See PMBus

Command 40h VOUT_OV_FAULT_LIMIT for details). The default output OVP limit is

set to 20% above nominal output voltage and responds by immediately shutdown

of main output and restarts when the fault condition no longer exists.

Over Current Protection (OCP, Current limit)

The module includes current limiting circuitry for protection at continuous over

load. The default setting for the product is hiccup mode. The current limit can be

configured by PMBus command 0x46, IOUT_OC_FAULT_LIMIT, to be greater than

the IOUT_OC_WARN_LIMIT (PMBus Command 0x4A). The maximum value that

the current limit could be set is 50A.

Power Good

The module provides Power Good (PG) flag in the STATUS_WORD register that

indicates the output voltage is within a specified tolerance of its target level and no

fault condition exists. The Power Good pin default logic is negative and it can be

configured by MFR_PGOOD_POLARITY.

Parallel Load Sharing (S Option, Droop Load Sharing)

Two or more converters may be connected in parallel at both the input and

output terminals to support higher output current or to improve reliability due to

the reduced stress that result when the modules are operating below their rated

limits. For applications requiring current share, followed the guidelines below. The

products have a pre-configured voltage droop. The stated output voltage set point

TECHNICAL & APPLICATIONS OVERVIEW

is at no load. The output voltage will decrease when the load current is increased.

The voltage will drop 0.35V while load reaches max load. Our goal is to have each

converter contribute nearly identical current into the output load under all input,

environmental and load conditions.

CAUTION: This converter is not internally fused. To avoid danger to persons or

equipment and to retain safety certification, the user must connect an external

fast-blow input fuse as listed in the specifications. Be sure that the PC board pad

area and etch size are adequate to provide enough current so that the fuse will

blow with an overload.

Using Parallel Connections – Redundancy (N+1)

The redundancy connections require external user supplied “OR”ing diodes or

“OR”ing MOSFETs for reliability purposes. The diodes allow for an uninterruptible

power system operation in case of a catastrophic failure (shorted output) by one of

the converters.

The diodes should be identical part numbers to enhance balance between the

converters. The default factory nominal voltage should be sufficiently matched

between converters. The OR’ing diode system is the responsibility of the user.

Be aware of the power levels applied to the diodes and possible heat sink

requirements.

Schottky power diodes with approximately 0.3V drops or “OR”ing MOSFETs may

be suitable in the loop whereas 0.7 V silicon power diodes may not be advisable.

In the event of an internal device fault or failure of the mains power modules on

the primary side, the other devices automatically take over the entire supply of

the loads. In the basic N+1 power system, the “N” equals the number of modules

required to fully power the system and “+1” equals one back-up module that will

take over for a failed module. If the system consists of two power modules, each

providing 50% of the total load power under normal operation and one module

fails, another one delivers full power to the load. This means you can use smaller

and less expensive power converters as the redundant elements, while achieving

the goal of increased availability.

Start Up Considerations

When power is first applied to the DC-DC converter, there is some risk of startup

difficulties if you do not have both low AC and DC impedance and adequate

regulation of the input source. Make sure that your source supply does not allow

the instantaneous input voltage to go below the minimum voltage at all times. Use

a moderate size capacitor very close to the input terminals. You may need two or

more parallel capacitors. A larger electrolytic or ceramic cap supplies the surge

current and a smaller parallel low-ESR ceramic cap gives low AC impedance.

Remember that the input current is carried both by the wiring and the ground

plane return. Make sure the ground plane uses adequate thickness copper. Run

additional bus wire if necessary.

Input Fusing

Certain applications and/or safety agencies may require fuses at the inputs of

power conversion components. Fuses should also be used when there is the pos-

sibility of sustained input voltage reversal which is not current-limited. For greatest

safety, we recommend a fast blow fuse installed in the ungrounded input supply

line.

SDC_DSQ_DAQ_DCQ0150V2.A04.D02 Page 13 of 25

DSQ/DAQ/DCQ Series

600W Quarter Brick

DOSA Digital PMBus Interface