LTC3615 LINER [Linear Technology], LTC3615 Datasheet - Page 13

• Manufacturer Part Number: LTC3615
• Description: Dual 4MHz, 3A Synchronous Step-Down DC/DC Converter
• Manufacturer: LINER [Linear Technology]

operaTion
Burst Mode Operation—External Clamp
Connecting the MODE pin to a voltage in the range of 0.5V
to 0.8V enables Burst Mode operation with external clamp.
During this mode of operation, the minimum voltage on the
ITH pin is externally set by the voltage on the MODE pin.
It is recommended to use Burst Mode operation with the
internal clamp for ambient temperatures above 85°C.
Pulse-Skipping Mode Operation
Pulse-skipping mode is similar to Burst Mode operation,
but the LTC3615 does not disable power to the internal
circuitry during sleep mode. This improves output voltage
ripple but uses more quiescent current compromising
light load efficiency.
Connecting the MODE pin to SV
mode. As the load current decreases, the peak inductor
current will be determined by the voltage on the ITH pin
until the ITH voltage drops below 450mV, corresponding
to 0A. At this point switching cycles will be skipped to
keep the output voltage in regulation.
V
0V
V
2a. Burst Mode Operation
Internally Controlled
0V
IN
IN
2c. Pulse-Skipping Mode
IN
SV
MODE
SGND
SV
MODE
SGND
enables pulse-skipping
IN
LTC3615
IN
LTC3615
Figure 2. Modes of Operation
V
0V
IN
Forced Continuous Mode Operation
In forced continuous mode the inductor current is con-
stantly cycled which creates a minimum output voltage
ripple at all output current levels.
Connecting the MODE pin, to a voltage in the range of
1.1V to SV
operation.
The forced continuous mode must be used if the output
is required to sink current.
Dropout Operation
As the input supply voltage approaches the output voltage,
the duty cycle increases toward the maximum on-time.
Further reduction of the supply voltage forces the main
switch to remain on for more than one cycle, eventually
reaching 100% duty cycle. The output voltage will then be
determined by the input voltage minus the voltage drop
across the internal P-channel MOSFET and the inductor.
V
0V
2d. Forced Continuous Mode
IN
SV
MODE
SGND
2b. Burst Mode Operation
Externally Controlled
IN
LTC3615
R
R
M1
M2
IN
SW1
• 0.58 will select the forced continuous mode
FB1
SV
MODE
SGND
IN
LTC3615
3615 F02
R
R
M1
M2
V
OUT1
LTC3615

3615f