LTM4606MPV datasheet(12/24 Pages) LINER

12 / 24 page

LTM4606

4606f

APPLICATIONS INFORMATION

Soft-Start and Tracking

The TRACK/SS pin provides a means to either soft-start

the regulator or track it to a different power supply. A

capacitor on this pin will program the ramp rate of the

output voltage. A 1.5μA current source will charge up the

external soft-start capacitor to 80% of the 0.6V internal

voltage reference minus any margin delta. This will control

the ramp of the internal reference and the output voltage.

The total soft-start time can be calculated as:

tV V

µA

SOFTSTART

OUT MARGIN

≅

()

0 8

.•

–

•

()

When the RUN pin falls below 2.5V, then the SS pin is reset

to allow for proper soft-start control when the regulator is

enabled again. Current foldback and force continuous mode

are disabled during the soft-start process. The soft-start

function can also be used to control the output ramp up time,

so that another regulator can be easily tracked to it.

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. Figure 4

shows an example of coincident tracking. Ratiometric

modes of tracking can be achieved by selecting different

resistor values to change the output tracking ratio. The

master output must be greater than the slave output for

the tracking to work. Figure 5 shows the coincident output

tracking characteristics.

DUTY CYCLE (VO/VIN)

0.1

0.15 0.2 0.25

0.35

0.3

0.4 0.45

0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

0.05

4612 F05

6-PHASE

4-PHASE

3-PHASE

2-PHASE

1-PHASE

Figure 3. Normalized Output Ripple Current vs Duty Cycle, Dlr = VOT/LI

Figure 4. Output Voltage Coincident Tracking

PGOOD

RUN

COMP

INTVCC

DRVCC

TRACK/SS

fSET

VOUT

VFB

FCB

MARG0

MARG1

MPGM

TRACK

CONTROL

PLLIN

LTM4606

19.1k

100k

19.1k

MASTER

OUTPUT

60.4k

COUT

SLAVE

OUTPUT

2.5V

4606 F04

CIN

VIN

PGND

SGND

VIN

LTM4606MPV Datasheet(PDF) 12 Page - Linear Technology

LTM4606MPV Datasheet(HTML) 12 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

Datasheet Download

Link URL