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ML6554

3A Bus Termination Regulator

Micro Linear Corporation 

ML6554

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 2).

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.

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 2.3V to 4V.

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 and 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.

TPI

VTT

TO SDRAMS

GND

4

R1 100Ω

R2 100Ω

C9 0.1µF

C8 0.1µF

C1

820µF

F2V

OS-CON

L1 3.3µH C3 0.1µF

C2

0.1µF

C4 0.1µF

U1

ML6554

1 VDD

2

PVDD1

3

VL1

4 PGND1

5

PGND2

6 VL2

7

PVDD2

8 DGND

16

AVCC

15

VCCQ

14

VREFOUT

13

AGND

SHDN 12

11

VREFIN

10

VFB

9

VDD

R4 100kΩ

R5 1kΩ

C7 1nF

R3

100kΩ

Figure 1.

2.5V TO 4V

220µF 220µF

VCCQ

VREFOUT

SHDN

VREFIN

GND

NOVEMBER, 1999

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