参数资料
型号: LT3493EDCB-3#TR
厂商: LINEAR TECHNOLOGY CORP
元件分类: 稳压器
英文描述: 2.2 A SWITCHING REGULATOR, 815 kHz SWITCHING FREQ-MAX, PDSO6
封装: 2 X 3 MM, PLASTIC, MO-229, DFN-6
文件页数: 18/20页
文件大小: 401K
代理商: LT3493EDCB-3#TR
7
LT3493-3
3493-3f
OPERATIO
U
The LT3493-3 is a constant frequency, current mode step-
down regulator. A 750kHz oscillator enables an RS flip-
flop, turning on the internal 1.75A power switch Q1. An
amplifier and comparator monitor the current flowing
between the VIN and SW pins, turning the switch off when
this current reaches a level determined by the voltage at
VC. An error amplifier measures the output voltage through
an external resistor divider tied to the FB pin and servos the
VC node. If the error amplifier’s output increases, more
current is delivered to the output; if it decreases, less
current is delivered. An active clamp (not shown) on the VC
node provides current limit. The VC node is also clamped
to the voltage on the SHDN pin; soft-start is implemented
by generating a voltage ramp at the SHDN pin using an
external resistor and capacitor.
An internal regulator provides power to the control cir-
cuitry. This regulator includes an undervoltage lockout to
prevent switching when VIN is less than 6.8V. The SHDN
pin is used to place the LT3493-3 in shutdown, discon-
necting the output and reducing the input current to less
than 2
A.
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 LT3493-3’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.
(Refer to Block Diagram)
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