LTC3803ES6#TRMPBF Linear Technology, LTC3803ES6#TRMPBF Datasheet - Page 8

• Manufacturer Part Number: LTC3803ES6#TRMPBF
• Description: IC FLYBACK SYNC ADJ 1A TSOT23-6
• Manufacturer: Linear Technology
• Type: Flybackr

Specifications of LTC3803ES6#TRMPBF

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: Adjustable
• Current - Output: 1A
• Frequency - Switching: 200kHz
• Voltage - Input: Adjustable
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: TSOT-23-6, TSOT-6
• Dc To Dc Converter Type: FLYBACK CONTROLLER
• Pin Count: 6
• Output Current: 1A
• Package Type: TSOT-23
• Mounting: Surface Mount
• Operating Temperature Classification: Automotive
• Operating Temperature (min): -40C
• Operating Temperature (max): 125C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Compliant
• Other names: LTC3803ES6#PBF; LTC3803ES6#PBF

OPERATION
LTC3803
The undervoltage lockout (UVLO) mechanism prevents the
LTC3803 from trying to drive a MOSFET with insuffi cient
V
(nominally 8.7V) at least momentarily to enable LTC3803
operation. The V
(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
0.28V) to force the LTC3803 into shutdown. An internal
0.3μA current source always tries to pull this pin towards
V
V
to operate and an internal clamp immediately pulls the
I
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
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.
8
TH
GS
CC
ITHSHDN
/RUN pin up to about 0.7V. In operation, the I
. When the I
. The voltage at the V
TH
/RUN pin can be driven below V
, and V
CC
CC
TH
voltage is then allowed to fall to V
/RUN pin voltage is allowed to exceed
exceeds V
CC
TURNON
pin must exceed V
, the LTC3803 begins
ITHSHDN
(nominally
TURNOFF
TH
TURNON
/RUN
TH
/
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
current as needed through this resistor to regulate the
V
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
from seeing too much voltage.
For higher effi ciency or for wide V
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
draw that is needed to support such bootstrapped hysteretic
start-up schemes.
The V
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.
CC
voltage to around 9.5V as long as the V
CC
pin must be bypassed to ground immediately
CC
pin to GND will draw as much
IN
range applications,
CC
supply current
CC
pin is not
CC
3803fc
pin