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LT8300E

100VIN Micropower Isolated Flyback Converter with 150V/260mA Switch

Analog Devices 

LT8300

PIN FUNCTIONS

EN/UVLO (Pin 1): Enable/Undervoltage Lockout. The

EN/UVLO pin is used to enable the LT8300. Pull the pin

below 0.3V to shut down the LT8300. This pin has an

accurate 1.223V threshold and can be used to program a

VIN undervoltage lockout (UVLO) threshold using a resis-

tor divider from VIN to ground. A 2.5µA current hysteresis

allows the programming of VIN UVLO hysteresis. If neither

function is used, tie this pin directly to VIN.

GND (Pin 2): Ground. Tie this pin directly to local ground

plane.

RFB (Pin 3): Input Pin for External Feedback Resistor.

Connect a resistor from this pin to the transformer

primary SW pin. The ratio of the RFB resistor to the inter-

nal trimmed 12.23k resistor, times the internal bandgap

reference, determines the output voltage (plus the effect

of any non-unity transformer turns ratio). Minimize trace

area at this pin.

SW (Pin 4): Drain of the 150V Internal DMOS Power

Switch. Minimize trace area at this pin to reduce EMI and

voltage spikes.

VIN (Pin 5): Input Supply. The VIN pin supplies current

to internal circuitry and serves as a reference voltage for

the feedback circuitry connected to the RFB pin. Locally

bypass this pin to ground with a capacitor.

BLOCK DIAGRAM

VIN

CIN

5

VIN

RFB

3

RFB

1:4

M3

M2

25µA

RREF

12.23kΩ

1.223V

R1

EN/UVLO

1

R2

2.5µA

1.223V

–

A1

+

M4

–

gm

+

OSCILLATOR

–

A3

+

VIN

REFERENCE

REGULATORS

BOUNDARY

DETECTOR

T1

NPS:1

DOUT

LPRI

•

•

LSEC

4

SW

VOUT+

COUT

VOUT–

S

RQ

DRIVER

M1

A2

RSENSE

0.3Ω

GND

2

6

For more information www.analog.com

8300 BD

Rev. A

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