LTC3836 LINER [Linear Technology], LTC3836 Datasheet - Page 13

• Manufacturer Part Number: LTC3836
• Description: Dual 2-Phase, No RSENSETM Low VIN Synchronous Controller
• Manufacturer: LINER [Linear Technology]

OPERATION
Figure 2 shows example waveforms for a single phase dual
controller versus a 2-phase LTC3836 system. In this case,
two outputs of different voltage, each drawing the same
load current are derived from a single input supply. In this
example, 2-phase operation could halve the RMS input
capacitor current. While this is an impressive reduction
by itself, remember that power losses are proportional
to I
is wasted.
SW1 (V)
SW2 (V)
RMS
I
I
I
L1
L2
IN
Figure 2. Example Waveforms for a Single Phase
Dual Controller vs the 2-Phase LTC3836
2
, meaning that just one-fourth the actual power
Dual Controller
Single Phase
(Refer to Functional Diagram)
Dual Controller
2-Phase
3836 F02
The reduced input ripple current also means that less power
is lost in the input power path, which could include batter-
ies, 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. Signifi cant cost and board footprint
savings are also realized by being able to use smaller, less
expensive, lower RMS current-rated input capacitors.
Of course, the improvement afforded by 2-phase operation
is a function of the relative duty cycles of the two control-
lers, which in turn are dependent upon the input supply
voltage. Figure 3 depicts how the RMS input current varies
for single phase and 2-phase dual controllers with 2.5V and
1.8V outputs. 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. RMS Input Current Comparison
1.2
2.0
1.8
1.6
1.4
1.0
0.8
0.6
0.4
0.2
0
3.0
V
V
OUT1
OUT2
DUAL CONTROLLER
SINGLE PHASE
= 2.5V/2A
= 1.8V/2A
INPUT VOLTAGE (V)
3.5
DUAL CONTROLLER
2-PHASE
4.0
LTC3836
3836 F03
4.5
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