SMS66 datasheet(12/26 Pages) SUMMIT

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SMS66

Preliminary Information

Summit Microelectronics, Inc

2070 1.0 7/16/03

APPLICATIONS INFORMATION

DEVICE OPERATION

POWER SUPPLY

The SMS66 can be powered by either a 12V input

through the 12VIN pin or by a 3.3V or 5.0V input

through the VDD pin. The 12VIN pin feeds an internal

programmable regulator that internally generates

either 5.5V or 3.6V. A voltage arbitration circuit allows

the device to be powered by the highest voltage from

either the regulator output or the VDD input. This

voltage arbitration circuit continuously checks for these

voltages to determine which will power the SMS66.

The resultant internal power supply rail is connected to

the VDD_CAP pin that allows both filtering and hold-

up of the internal power supply.

MODES OF OPERATION

The SMS66 has three basic modes of operation:

Power-on sequencing mode, monitoring mode, and

Power-off sequencing mode (shown in Figures 4B

through 4E). In addition, there is a forced shutdown

feature.

A detailed description of each mode and

feature follows.

POWER-ON SEQUENCING

The SMS66 can be programmed to sequence up to six

power supplies in any order.

Each of these six

channels (A-F) has an associated open drain PUP

output that, when connected to a converter’s enable

pin, controls the turn-on of the converter.

The

channels

are

assigned

sequence

positions

determine the order of the sequence. Any channel

can also be programmed to not take part in the

sequencing in applications with fewer than six

supplies. The polarity of each of the PUPX outputs is

programmable

for

use

with

various

types

converters.

Power-on sequencing can be initiated by the

PWR_ON/OFF pin or via I

2C control. The polarity of

the PWR_ON/OFF pin is programmable. If hard wired

in its active state the SMS66 will automatically initiate

the Power-on sequence.

Otherwise, toggling the

PWR_ON/OFF pin to its active state will initiate the

Power-on sequence. To enable software control of

the sequencing feature, the SMS66 offers an I

command to initiate Power-on sequencing while the

PWR_ON/OFF pin is in its inactive state.

Figure 4D:

SMS66 Sequence-On Waveforms

Time/Horizontal division = 40mS

Ch 1(500mV/Div) = 3.3V DC-DC converter output (Yellow trace)

Ch 2 (500mV/Div) = 2.5V DC-DC converter output (Blue trace)

Ch 3 (500mV/Div) = 1.8V DC-DC converter output (Purple trace)

Ch 4 (500mV/Div) = 1.5V DC-DC converter output (Green trace)

Figure 4E SMS66 Sequence-Off Waveforms

Time/Horizontal division = 400mS

Ch 1(500mV/Div) = 3.3V DC-DC converter output (Yellow trace)

Ch 2 (500mV/Div) = 2.5V DC-DC converter output (Blue trace)

Ch 3 (500mV/Div) = 1.8V DC-DC converter output (Purple trace)

Ch 4 (500mV/Div) = 1.5V DC-DC converter output (Green trace)

SMS66 Datasheet(PDF) 12 Page - Summit Microelectronics, Inc.

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