LTC2928I データシートの表示（PDF） - Linear Technology

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LTC2928I

Multichannel Power Supply Sequencer and Supervisor

Linear Technology 

LTC2928

Applications Information

Another interesting application combines the usage of both

the CAS pin connection and the DONE—ON communica-

tions link. Figure 4 shows a two dimensional configura-

tion of four LTC2928s that allows for 16 supplies to be

sequenced in up to 16 time positions.

16 SUPPLIES, 16 TIME POSITIONS

(MASTER/FIRST)

(MASTER/NOT FIRST)

LTC2928

ON

LTC2928

ON

VCC

DONE

DONE

Using an Enable Line to Generate a Sequencing-Up Delay

LTC2928

VCC

RT2

EN2

IEN (10µA)

V2

CDEL

2928 F05

Figure 5. Adjustable Sequencing Delay

STMR

CAS

STMR

CAS

CAS

ON

VCC

ON

CAS

VCC

An arbitrary delay between enables may be added by

using an enable pull-up current (10µA) to charge a delay

capacitor (Figure 5). Position the delay using an RT resis-

tor. Assuming 100% sequencing thresholds (0.5V) and

a fully discharged delay capacitor (CDEL), the added time

delay (TDEL) is:

DONE

DONE

LTC2928

(SLAVE/FIRST)

LTC2928

(SLAVE/FIRST)

2928 F04

Figure 4. Two-dimensional application.

In this application, both slave devices are clocked by the

masters through their CAS pins. Again, sequencing-up

begins with ON pulling high. Although the ON input is high

on the device in the lower right quadrant, sequencing-up

will not begin there until the first master (upper left), and

its slave are finished sequencing-up. At that time the

DONE pin will pull up the ON pin of the second master.

The second master and slave will then start sequencing

up their supplies.

TDEL(ms) = 50•CDEL(µF)

Be sure to account for the extra delay when using the

power-good timer (PTMR).

Extending Sequencing Delay to Subsequent Supplies

Sequencing delays can be extended after certain events by

paralleling capacitance to the STMR pin. Figure 6 shows

one way to add capacitance after a particular enable output

pulls high.

LTC2928

EN2

VCC

RESISTOR LIMITS

GATE VOLTAGE

STMR

CSTMR

CADD

2928 F06

Figure 6. Adding STMR capacitance

For more information www.linear.com/LTC2928

2928fa

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