Linear Technology LTM4608AEV DEMO BOARD, 2.7Vinmin, 8A DC/DC µModule Regulator DC1400A DC1400A 데이터 시트

LTM4608A

10

4608afd

With current mode control and internal feedback loop 

compensation, the LTM4608A module has sufficient 

stability margins and good transient performance with 

a wide range of output capacitors, even with all ceramic 

output capacitors.
Current mode control provides cycle-by-cycle fast current 

limit and thermal shutdown in an overcurrent condition. 

Internal overvoltage and undervoltage comparators pull 

the open-drain PGOOD output low if the output feedback 

voltage exits a ±10% window around the regulation point.
Pulling the RUN pin below 1.3V forces the controller into 

its shutdown state, by turning off both M1 and M2 at low 

load current. The TRACK pin is used for programming the 

output voltage ramp and voltage tracking during start-up. 

See Applications Information.
The LTM4608A is internally compensated to be stable 

over all operating conditions. Table 3 provides a guideline 

for input and output capacitances for several operating 

The typical LTM4608A application circuit is shown in 

Figure 18. External component selection is primarily 

determined by the maximum load current and output 

voltage. Refer to Table 3 for specific external capacitor 

requirements for a particular application.

There are restrictions in the maximum V

IN

 to V

OUT

 step-

down ratio that can be achieved for a given input voltage. 

The LTM4608A is 100% duty cycle, but the V

IN

 to V

OUT

 

minimum dropout is a function of its load current. Please 

refer to the curves in the Typical Performance Charac-

teristics section of this data sheet for more information.

Output Voltage Programming
The PWM controller has an internal 0.596V reference 

voltage. As shown in the Block Diagram, a 10k 0.5% 

internal feedback resistor connects V

OUT

 and FB pins 

together. The output voltage will default to 0.596V with 

conditions. The Linear Technology µModule Power Design 

Tool is provided for transient and stability analysis. The 

FB pin is used to program the output voltage with a single 

external resistor to ground.
Multiphase operation can be easily employed with the 

synchronization and phase mode controls. Up to 12 phases 

can be cascaded to run simultaneously with respect to 

each other by programming the PHMODE pin to different 

levels. The LTM4608A has clock in and clock out for poly 

phasing multiple devices or frequency synchronization.
High efficiency at light loads can be accomplished with 

selectable Burst Mode operation using the MODE pin. These 

light load features will accommodate battery operation. 

Efficiency graphs are provided for light load operation in 

the Typical Performance Characteristics.
Output voltage margining is supported, and can be pro-

gramed from ±5% to ±15% using the MGN and BSEL pins. 

The PGOOD pin is disabled during margining

no feedback resistor. Adding a resistor R

FB

 from FB pin 

to GND programs the output voltage:

 

 

V

OUT

= 0.596V •

10k

+R

FB

R

FB

V

OUT

0.596V

1.2V

1.5V

1.8V

2.5V

3.3V

R

FB

Open

10k

6.65k

4.87k

3.09k

2.21k

Input Capacitors
The LTM4608A module should be connected to a low AC 

impedance DC source. Three 10µF ceramic capacitors 

are included inside the module. Additional input capaci-

tors are only needed if a large load step is required up to 

the 4A level. A 47µF to 100µF surface mount aluminum 

electrolytic bulk capacitor can be used for more input bulk 

capacitance. This bulk input capacitor is only needed if 

the input source impedance is compromised by long in-

ductive leads, traces or not enough source capacitance.