LT3799I(RevA) 查看數據表（PDF） - Linear Technology

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LT3799I
(Rev.:RevA)

Offline Isolated Flyback LED Controller with Active PFC

Linear Technology 

LT3799

Pin Functions

CTRL1, CTRL2, CTRL3 (Pin 1, Pin 2, Pin 3): Current Output

Adjustment Pins. These pins control the output current.

The lowest value of the three CTRL inputs is compared to

the negative input of the operational amplifier. Due to the

unique nature of the LT3799 control loop, the maximum

current does not directly correspond to the VCTRL voltages.

VREF (Pin 4): Voltage Reference Output Pin, Typically 2V.

This pin drives a resistor divider for the CTRL pin, either

for analog dimming or for temperature limit/compensation

of LED load. Can supply up to 200µA.

FAULT (Pin 5): Fault Pin. An open-collector pull-down on

FAULT asserts if FB is greater than 1.25V with the CT pin

higher than 1.25V.

CT (Pin 6): Timer Fault Pin. A capacitor is connected

between this pin and ground to provide an internal timer

for fault operations. During start-up, this pin is pulled to

ground and then charged with a 10µA current. Faults related

to the FB pin will be ignored until the CT pin reaches 1.25V.

If a fault is detected, the controller will stop switching and

begin to discharge the CT capacitor with a 200nA pull-down

current. When the pin reaches 240mV, the controller will

start to switch again.

COMP+, COMP– (Pin 7, Pin 8): Compensation Pins for

Internal Error Amplifier. Connect a capacitor between these

two pins to compensate the internal feedback loop.

FB (Pin 9): Voltage Loop Feedback Pin. FB is used to

detect open LED conditions by sampling the third winding

voltage. An open LED condition is reported if the CT pin

and the FB pin are higher than 1.25V.

DCM (Pin 10): Discontinuous Conduction Mode Detection

Pin. Connect a capacitor and resistor in series with this

pin to the third winding.

VIN (Pin 11): Input Voltage. This pin supplies current to

the internal start-up circuitry and to the INTVCC LDO. This

pin must be locally bypassed with a capacitor. A 25V shunt

regulator is internally connected to this pin.

INTVCC (Pin 13): Regulated Supply for Internal Loads

and GATE Driver. Supplied from VIN and regulates to 10V

(typical). INTVCC must be bypassed with a 4.7µF capacitor

placed close to the pin.

GATE (Pin 14): N-Channel MOSFET Gate Driver Output.

Switches between INTVCC and GND. This pin is pulled to

GND during shutdown state.

SENSE (Pin 15): The Current Sense Input for the Control

Loop. Kelvin connect this pin to the positive terminal of

the switch current sense resistor, RSENSE, and the source

of the N-channel MOSFET. The negative terminal of the

current sense resistor should be connected to the GND

plane close to the IC.

VIN_SENSE (Pin 16): Line Voltage Sense Pin. The pin is used

for sensing the AC line voltage to perform power factor

correction. Connect the output of a resistor divider from

the line voltage to this pin. The voltage on this pin should

be between 1.25V to 1.5V at the maximum input voltage.

GND (Exposed Pad Pin 17): Ground. The exposed pad

of the package provides both electrical contact to ground

and good thermal contact to the printed circuit board.

The exposed pad must be soldered to the circuit board

for proper operation.

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