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ML6554CU

3A Bus Termination Regulator

Fairchild Semiconductor 

ML6554

PRODUCT SPECIFICATION

Functional Description

This switching regulator is capable of sinking and sourcing

3A of current without an external heatsink. The ML6554

uses a power surface mount package (PSOP) that includes

an integrated heat slug. The heat can be piped through the

bottom of the device and onto the PCB (Figure 1).

The ML6554 integrates two power MOSFETs that can be

used to source and sink 3A of current while maintaining a

tight voltage regulation. Using the external feedback, the

output can be regulated well within 3% or less, depending on

the external components chosen. Separate voltage supply

inputs have been added to accommodate applications with

various power supplies for the databus and power buses, see

Figure 2.

Outputs

The output voltage pins (VL1, VL2) are tied to the databus,

address, or clock lines via an external inductor. See the

Applications section for recommendations. Output voltage

is determined by the VCCQ or VREFIN inputs.

Inputs

The input voltage pins (VCCQ or VREFIN) determine the

output voltages (VL1 or VL2) . In the default mode, where

the VREFIN pin is floating, the output voltage is 50% of the

VCCQ input. VCCQ can be the reference voltage for the

databus.

Output voltage can also be selected by forcing a voltage at

the VREFIN pin. In this case, the output voltage follows the

voltage at the VREFIN input. Simple voltage dividers can be

used this case to produce a wide variety of output voltages

between 0.7V and VDD–0.7V.

VREF Input and Output

The VREFIN input can be used to force a voltage at the

outputs (Inputs section, above). The VREFOUT pin is an

output pin that is driven by a small output buffer to provide

the VREF signal to other devices in the system. The output

buffer is capable of driving several output loads. The output

buffer can handle 3mA.

Other Supply Voltages

Several inputs are provide for the supply voltages: PVDD1,

PVDD2, AVCC, and VDD.

The PVDD1 and PVDD2 provide the power supply to the

power MOSFETs. VDD provides the voltage supply to the

digital sections, while AVCC supplies the voltage for the

analog sections. Again, see the Applications section for

recommendations.

Feedback Input

The VFB pin is an input that can be used for closed loop

compensation. This input is derived from the voltage output.

See application section for recommendation.

HEAT SLUG

Figure 1. Cutaway view of PSOP Package

4

REV. 1.1.3 3/8/02

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