LTC3425 Linear Technology, LTC3425 Datasheet - Page 13

• Manufacturer Part Number: LTC3425
• Description: 5A 8MHz 4-Phase Synchronous Step-Up DC/DC Converter
• Manufacturer: Linear Technology

OPERATIO
internally controlled. The device can start up under some
load (see the graph Start-Up Current vs Input Voltage).
Soft-start and inrush current limiting is provided during
start-up as well as normal mode. The same soft-start
capacitor is used for each operating mode.
During start-up, all four phases switch in unison. When
either V
operating mode. Once the output voltage exceeds the
IN
or V
OUT
U
exceeds 2.3V, the IC enters normal
INPUT CURRENT
OUTPUT RIPPLE
INDUCTOR D
INDUCTOR A
INDUCTOR B
INDUCTOR C
RECTIFIER A
RECTIFIER B
RECTIFIER C
RECTIFIER D
SWITCH D
SWITCH A
SWITCH B
SWITCH C
CURRENT
CURRENT
CURRENT
CURRENT
CURRENT
CURRENT
CURRENT
CURRENT
CURRENT
VOLTAGE
VOLTAGE
VOLTAGE
VOLTAGE
Figure 3. Simplified Voltage and Current Waveforms
for 4-Phase Operation at 75% Duty Cycle
input by 0.3V, the IC powers itself from V
V
on the V
large input capacitor. The input voltage can drop as low as
0.5V without affecting circuit operation. The limiting factor
for the application becomes the ability of the power source
to supply sufficient energy to the output at the low volt-
ages, and the maximum duty cycle that is clamped at 90%.
IN
. At this point the internal circuitry has no dependency
IN
input voltage, eliminating the requirement for a
3432 F03
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LTC3425
OUT
instead of
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