参数资料
型号: LT3502AEDC#PBF
厂商: LINEAR TECHNOLOGY CORP
元件分类: 稳压器
英文描述: 1.1 A SWITCHING REGULATOR, 2800 kHz SWITCHING FREQ-MAX, PDSO8
封装: 2 X 2 MM, LEAD FREE, PLASTIC, DFN-8
文件页数: 24/24页
文件大小: 386K
代理商: LT3502AEDC#PBF
LT3502/LT3502A
9
3502fd
The LT3502/LT3502A are constant frequency, current
mode step-down regulators. An oscillator enables an RS
ip-op, turning on the internal 500mA power switch Q1.
An amplier and comparator monitor the current owing
between the VIN and SW pins, turning the switch off when
this current reaches a level determined by the voltage at
VC. An error amplier measures the output voltage through
an external resistor divider tied to the FB pin and servos
the VC node. If the error amplier’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. The SHDN pin voltage
during soft-start also reduces the oscillator frequency to
avoid hitting current limit during start-up.
An internal regulator provides power to the control cir-
cuitry. This regulator includes an undervoltage lockout to
prevent switching when VIN is less than ~3V. The SHDN
pin is used to place the LT3502/LT3502A in shutdown,
disconnecting the output and reducing the input current
to less than 2μA.
The switch driver operates from either VIN or from the
BOOST pin. An external capacitor and the internal 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
efcient operation.
A comparator monitors the current owing through
the catch diode via the DA pin and reduces the LT3502/
LT3502A’s operating frequency when the DA pin current
exceeds the 650mA valley current limit. This frequency
foldback helps to control the output current in fault
conditions such as shorted output with high input volt-
age. The DA comparator works in conjunction with the
switch peak current limit comparator to determine the
maximum deliverable current of the LT3502/LT3502A. The
peak current limit comparator is used in normal current
mode operations and is used to turn off the switch. The DA
valley current comparator monitors the catch diode current
and will delay switching until the catch diode current is
below the 650mA limit. Maximum deliverable current to
the output is therefore limited by both switch peak current
limit and DA valley current limit.
OPERATION
相关PDF资料
PDF描述
LT3502AIDC#PBF 1.1 A SWITCHING REGULATOR, 2800 kHz SWITCHING FREQ-MAX, PDSO8
LT3502AIDC#TR 1.1 A SWITCHING REGULATOR, 2800 kHz SWITCHING FREQ-MAX, PDSO10
LT3502AEDC#TRM 1.1 A SWITCHING REGULATOR, 2800 kHz SWITCHING FREQ-MAX, PDSO10
LT3502IDC#TR 1.1 A SWITCHING REGULATOR, 1400 kHz SWITCHING FREQ-MAX, PDSO10
LT3502IDC#TRM 1.1 A SWITCHING REGULATOR, 1400 kHz SWITCHING FREQ-MAX, PDSO10
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