LTM4604 datasheet(11/20 Pages) LINER

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LTM4604

4604f

Ratio metric 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. Linear Technology Tracker Cad26

can be used to implement different tracking scenarios. 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 require-

ments. A spice model will be provided for other control

loop optimizations.

APPLICATIONS INFORMATION

Parallel Operation

The LTM4604 device is an inherently current mode con-

trolled 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

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

4604 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

4604 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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