lt8415 Linear Technology Corporation, lt8415 Datasheet - Page 7

• Manufacturer Part Number: lt8415
• Description: Ultralow Power Boost Converter With Dual Half-bridge Switches
• Manufacturer: Linear Technology Corporation

TIMING DIAGRAM
OPERATION
Switching Regulator
The LT8415 utilizes a variable peak current, variable off-
time control scheme to provide high effi ciency over a wide
output current range.
The operation of the part can be better understood by
referring to the Block Diagram. The part senses the
output voltage by monitoring the internal FB node, and
servoing the FB node voltage to be equal to the FBP
pin voltage. The chip integrates an accurate high value
resistor divider (12.4MEG/0.4MEG) from the V
The output voltage is set by the FBP pin voltage, which
in turn is set by an external resistor divider from the V
pin. The FBP pin voltage can also be directly biased with
an external reference, allowing full control of the output
voltage during operation.
The Switch Control block senses the output of the ampli-
fi er and adjusts the switching frequency as well as other
parameters to achieve regulation. During the start-up of
OUT1,OUT2
VOLTAGE
VOLTAGE
IN1,IN2
34V
2V
0V
0V
DELAY
RISE
TIME
RISE
4V
OUT
pin.
REF
30V
the circuit, special precautions are taken to ensure that
the inductor current remains under control.
The LT8415 also has a PMOS output disconnect switch.
The PMOS switch is turned on when the part is enabled
via the SHDN pin. When the part is in shutdown, the
PMOS switch turns off, allowing the V
ground. This type of disconnect function is often required
in power supplies.
Half-Bridge
The N-channel and P-channel MOSFETs in each half-bridge
are synchronously controlled by a single input pin, and
will never turn on at the same time in typical applications,
protecting against shoot-through current. The OUT1 and
OUT2 pins are the same polarity as the IN1 and IN2 pins
respectively. When the part is disabled, both N-channel
and P-channel MOSFETs turn off, and the OUT1 and OUT2
pins will become high impedance with a 20MΩ pull down
resistor connected to ground.
DELAY
FALL
TIME
FALL
8415 TD
OUT
LT8415
node to go to
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