LTC3728L-1

12

3728l1fc

Figure 3 compares the input waveforms for a representa-

tive single-phase dual switching regulator to the LTC1628

2-phase dual switching regulator. An actual measurement of

the RMS input current under these conditions shows that 2-

meaning that the actual power wasted is reduced by a fac-

tor of 2.66. The reduced input ripple voltage also means

less power is lost in the input power path, which could

include batteries, switches, trace/connector resistances

and protection circuitry. Improvements in both conducted

and radiated EMI also directly accrue as a result of the

reduced RMS input current and voltage.

Of course, the improvement afforded by 2-phase opera-

tion is a function of the dual switching regulator’s relative

duty cycles which, in turn, are dependent upon the input

the RMS input current varies for single-phase and 2-phase

operation for 3.3V and 5V regulators over a wide input

voltage range.

It can readily be seen that the advantages of 2-phase opera-

tion are not just limited to a narrow operating range, but

in fact extend over a wide region. A good rule of thumb

for most applications is that 2-phase operation will reduce

the input capacitor requirement to that for just one channel

operating at maximum current and 50% duty cycle.

Figure 3. Input Waveforms Comparing Single-Phase (a) and 2-Phase (b) Operation for Dual Switching Regulators

Converting 12V to 5V and 3.3V at 3A Each. The Reduced Input Ripple with the LTC1628 2-Phase Regulator Allows

Less Expensive Input Capacitors, Reduces Shielding Requirements for EMI and Improves Efficiency

3728L1 F03a

5V SWITCH

20V/DIV

3.3V SWITCH

20V/DIV

INPUT CURRENT

5A/DIV

INPUT VOLTAGE

500mV/DIV

3728L1 F03b

(a)

(b)

Figure 4. RMS Input Current Comparison

INPUT VOLTAGE (V)

0

3.0

2.5

2.0

1.5

1.0

0.5

0

10

20

30

40

3728L1 F04

SINGLE PHASE

DUAL CONTROLLER

2-PHASE

DUAL CONTROLLER