LTM4613 datasheet(15/30 Pages) LINER

15 / 30 page

LTM4649

4649fc

For more information www.linear.com/LTM4649

APPLICATIONS INFORMATION

INTVCC. After ramping to 0.6V, the TRACK/SS pin will no

longer be in control, and the internal voltage reference

will control output regulation from the feedback divider.

Foldback current limit is disabled during this sequence of

turn-on during tracking or soft-starting. The TRACK/SS

pin is pulled low when the RUN pin is below 1.2V. The

total soft-start time can be calculated as:

tSS =

CSS

1.2µA











 • 0.6V

Regardless of the mode selected by the MODE pin, the

regulator will always start in pulse-skipping mode up to

TRACK/SS = 0.5V. Between TRACK/SS = 0.5V and 0.54V,

it will operate in forced continuous mode and revert to the

selected mode once TRACK/SS > 0.54V. In order to track

with another regulator once in steady state operation,

the LTM4649 is forced into continuous mode operation

as soon as VFB is below 0.54V regardless of the setting

on the MODE pin.

Output Voltage Tracking

Output voltage tracking can be programmed externally

using the TRACK/SS pin. The output can be tracked up

and down with another regulator. The master regulator’s

output is divided down with an external resistor divider

that is the same as the slave regulator’s feedback divider

to implement coincident tracking. The LTM4649 uses an

accurate 10k resistor internally for the top feedback resis-

tor. Figure 6 shows the coincident tracking characteristic.

VSLAVE = 1+

10k

RTA











 • VTRACK

VTRACK is the track ramp applied to the slave’s track pin.

VTRACK has a control range of 0V to 0.6V, or the internal

reference voltage. When the master’s output is divided

COMP

TRACK/SS

RUN

FREQ

MODE

PGOOD

VOUT

VOUT_LCL

DIFFOUT

DIFFP

DIFFN

VFB

LTM4649

VIN

10k

RFB1

6.65k

C10

22µF

16V

22µF

16V

CSS

SOFT-START

CAPACITOR

VOUT2

1.5V

10A

C11

100µF

6.3V

×2

INTVCC

VIN

GND

COMP

TRACK/SS

RUN

FREQ

MODE

PGOOD

VOUT

VOUT_LCL

DIFFOUT

DIFFP

DIFFN

VFB

LTM4649

VIN

10k

RFB

10k

22µF

16V

22µF

16V

100µF

6.3V

×2

VOUT1

1.2V

10A

INTVCC

4649 F05

GND

RTB

10k

RTA

10k

MASTER RAMP

OR OUTPUT

VIN

Figure 5. Dual Outputs (1.5V and 1.2V) with Tracking

LTM4613 Datasheet(PDF) 15 Page - Linear Technology

LTM4613 Datasheet(HTML) 15 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Datasheet Download

Link URL