LTM4604A datasheet(11/20 Pages) LINER

11 / 20 page

LTM4604A

4604af

Ratio metric modes of tracking can be achieved by select-

ing different resistor values to change the output tracking

ratio. The master output must be greater than the slave

output for the tracking to work. Linear Technology Tracker

Cad26 can be used to implement different tracking sce-

narios. The Master and Slave data inputs can be used to

implement the correct resistor values for coincident or

ratio tracking. The master and slave regulators require

load current for tracking down.

Power Good

The PGOOD pin is an open-drain pin that can be used to

monitor valid output voltage regulation. This pin monitors

a ±7.5% window around the regulation point.

COMP Pin

The pin is the external compensation pin. The module has

already been internally compensated for all output voltages.

Table 4 is provided for most application requirements.

The Linear Technology μModule Power Design Tool can

be provided for other control loop optimizations.

APPLICATIONS INFORMATION

Parallel Operation

The LTM4604A device is an inherently current mode

controlled device. Parallel modules will have very good

current sharing. This will balance the thermals on the

design. Figure 16 shows a schematic of the parallel design.

The voltage feedback changes with the variable N as more

modules are paralleled. The equation:

OUT

0 8

499

.•

N is the number of paralleled modules.

Thermal Considerations and Output Current Derating

The power loss curves in Figures 4 and 5 can be used

in coordination with the load derating curves in Figures

6 through 13 for calculating an approximate θJA for the

module with and without heat sinking methods with vari-

ous airﬂow conditions. Thermal models are derived from

several temperature measurements at the bench, and are

correlated with thermal analysis software. Tables 2 and

3 provide a summary of the equivalent θJA for the noted

conditions. These equivalent θJAparametersarecorrelated

to the measured values and improve with air ﬂow. The

maximum junction temperature is monitored while the

derating curves are derived.

Figure 4. 1.2V Power Loss

Figure 5. 2.5V Power Loss

LOAD CURRENT (A)

0.4

0.6

0.8

1.0

1.2

1.4

4604A F04

1.6

1.8

2.0

0.2

5V TO 1.2V

POWER LOSS

3.3V TO 1.2V

POWER LOSS

LOAD CURRENT (A)

0.4

0.6

0.8

1.0

1.2

1.4

234

4604A F05

1.6

1.8

2.0

0.2

5V TO 2.5V

POWER LOSS

3.3V TO 2.5V

POWER LOSS

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