Datasheet 搜索 > 稳压芯片 > Linear Technology（凌力尔特） > LTC3803HS6#TRPBF 数据手册 > LTC3803HS6#TRPBF 数据手册 8/16 页
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LTC3803HS6#TRPBF 数据手册 - Linear Technology（凌力尔特）
制造商:
Linear Technology（凌力尔特）
分类:
稳压芯片
封装:
TSOT-23-6
Pictures:
3D模型
符号图
焊盘图
引脚图
产品图
页面导航:
引脚图在P6Hot
典型应用电路图在P1P12P13P16
原理图在P6P7
封装尺寸在P14
焊盘布局在P14
技术参数、封装参数在P4
应用领域在P1P4P8P9P10P11P12P13P16
电气规格在P3P4P5
导航目录
LTC3803HS6#TRPBF数据手册
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LTC3803
8
3803fc
OPERATION
The undervoltage lockout (UVLO) mechanism prevents the
LTC3803 from trying to drive a MOSFET with insuffi cient
V
GS
. The voltage at the V
CC
pin must exceed V
TURNON
(nominally 8.7V) at least momentarily to enable LTC3803
operation. The V
CC
voltage is then allowed to fall to V
TURNOFF
(nominally 5.7V) before undervoltage lockout disables the
LTC3803. This wide UVLO hysteresis range supports the
use of a bias winding on the fl yback transformer to power
the LTC3803—see the section Powering the LTC3803.
The I
TH
/RUN pin can be driven below V
ITHSHDN
(nominally
0.28V) to force the LTC3803 into shutdown. An internal
0.3µA current source always tries to pull this pin towards
V
CC
. When the I
TH
/RUN pin voltage is allowed to exceed
V
ITHSHDN
, and V
CC
exceeds V
TURNON
, the LTC3803 begins
to operate and an internal clamp immediately pulls the
I
TH
/RUN pin up to about 0.7V. In operation, the I
TH
/RUN
pin voltage will vary from roughly 0.7V to 1.9V to represent
current comparator thresholds from zero to maximum.
Internal Soft-Start
An internal soft-start feature is enabled whenever the
LTC3803 comes out of shutdown. Specifi cally, the I
TH
/
RUN voltage is clamped and is prevented from reaching
maximum until roughly 1.4ms has passed. This allows
the input and output currents of LTC3803-based power
supplies to rise in a smooth and controlled manner on
start-up.
Powering the LTC3803
In the simplest case, the LTC3803 can be powered from
a high voltage supply through a resistor. A built-in shunt
regulator from the V
CC
pin to GND will draw as much
current as needed through this resistor to regulate the
V
CC
voltage to around 9.5V as long as the V
CC
pin is not
forced to sink more than 25mA. This shunt regulator is
always active, even when the LTC3803 is in shutdown,
since it serves the vital function of protecting the V
CC
pin
from seeing too much voltage.
For higher effi ciency or for wide V
IN
range applications,
fl yback controllers are typically powered through a separate
bias winding on the fl yback transformer. The LTC3803 has
the wide UVLO hysteresis and small V
CC
supply current
draw that is needed to support such bootstrapped hysteretic
start-up schemes.
The V
CC
pin must be bypassed to ground immediately
adjacent to the IC pins with a minimum of a 10µF ceramic
or tantalum capacitor. Proper supply bypassing is neces-
sary to supply the high transient currents required by the
MOSFET gate driver.
Adjustable Slope Compensation
The LTC3803 injects a 5µA peak current ramp out through
its SENSE pin which can be used for slope compensation in
designs that require it. This current ramp is approximately
linear and begins at zero current at 6% duty cycle, reach-
ing peak current at 80% duty cycle. Additional details are
provided in the Applications Information section.
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