LT1912EMSE#PBF Linear Technology, LT1912EMSE#PBF Datasheet - Page 8

• Manufacturer Part Number: LT1912EMSE#PBF
• Description: IC, STEP-DOWN REGULATOR, MSOP-10
• Manufacturer: Linear Technology

Specifications of LT1912EMSE#PBF

• Primary Input Voltage: 36V
• No. Of Outputs: 1
• Output Voltage: 20V
• Output Current: 2A
• No. Of Pins: 10
• Operating Temperature Range: -40°C To +125°C
• Supply Voltage Range: 3.6V To 36V
• Msl: MSL 1 - Unlimited
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

OPERATION
LT1912
The LT1912 is a constant frequency, current mode step-
down regulator. An oscillator, with frequency set by R
enables an RS flip-flop, turning on the internal power
switch. An amplifier and comparator monitor the current
flowing 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
8
C
pin provides current limit. The V
C
. An error amplifier measures the output
C
IN
pin. If the error amplifier’s output
and SW pins, turning the switch
C
pin is also clamped to
IN
pin,
T
,
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
efficiency. The RUN/SS pin is used to place the LT1912
in shutdown, disconnecting the output and reducing the
input current to less than 1µA.
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
the input supply. This allows the driver to fully saturate the
internal bipolar NPN power switch for efficient operation.
The oscillator reduces the LT1912’s operating frequency
when the voltage at the FB pin is low. This frequency
foldback helps to control the output current during start-
up and overload.
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