LT3980EDE#TRPBF Linear Technology, LT3980EDE#TRPBF Datasheet - Page 8

• Manufacturer Part Number: LT3980EDE#TRPBF
• Description: IC SWITCHING REG STP-DN 2A 14DFN
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LT3980EDE#TRPBF

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 0.79 ~ 52.2 V
• Current - Output: 2A
• Frequency - Switching: 100kHz ~ 2.4MHz
• Voltage - Input: 3.6 ~ 58 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 14-DFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

OPERATION
LT3980
The LT3980 is a constant frequency, current mode step-
down regulator. An oscillator, with frequency set by RT,
enables an RS fl ip-fl op, turning on the internal power
switch. An amplifi er and comparator monitor the current
fl owing between the V
off when this current reaches a level determined by the
voltage at V
voltage through an external resistor divider tied to the FB
pin and servos the V
increases, more current is delivered to the output; if it
decreases, less current is delivered. An active clamp on the
V
the voltage on the RUN/SS pin; soft-start is implemented
by generating a voltage ramp at the RUN/SS pin using an
external resistor and capacitor.
An internal regulator provides power to the control circuitry.
The bias regulator normally draws power from the V
but if the BD pin is connected to an external voltage higher
than 3V bias power will be drawn from the external source
(typically the regulated output voltage). This improves
effi ciency. The RUN/SS pin is used to place the LT3980
in shutdown, disconnecting the output and reducing the
input current to less than 0.5μA.
The switch driver operates from either the input or from
the BOOST pin. An external capacitor and diode are used
to generate a voltage at the BOOST pin that is higher than
8
C
pin provides current limit. The V
C
. An error amplifi er measures the output
C
IN
pin. If the error amplifi er’s output
and SW pins, turning the switch
C
pin is also clamped to
IN
pin,
the input supply. This allows the driver to fully saturate
the internal bipolar NPN power switch for effi cient opera-
tion.
To further optimize effi ciency, the LT3980 automatically
switches to Burst Mode operation in light load situations.
Between bursts, all circuitry associated with controlling
the output switch is shut down, reducing the input supply
current to 75μA in a typical application.
The oscillator reduces the LT3980’s operating frequency
when the voltage at the FB pin is low. This frequency
foldback helps to control the output current during startup
and overload. In addition, the LT3980 monitors the catch
diode current fl owing through the DA pin and pauses the
oscillator during overcurrent conditions to keep inductor
current at safe levels.
The LT3980 contains a power good comparator which trips
when the FB pin is at 91% of its regulated value. The PG
output is an open-collector transistor that is off when the
output is in regulation, allowing an external resistor to pull
the PG pin high. Power good is valid when the LT3980 is
enabled and V
The LT3980 has an overvoltage protection feature which
disables switching action when the V
typical (58V minimum). When switching is disabled, the
LT3980 can safely sustain input voltages up to 62V.
IN
is above 3.6V.
IN
goes above 61.5V
3980f