Datasheet LT8300 (Analog Devices) - 6

LT8300
PIN FUNCTIONS EN/UVLO (Pin 1):
Enable/Undervoltage Lockout. The primary SW pin. The ratio of the RFB resistor to the inter- EN/UVLO pin is used to enable the LT8300. Pull the pin nal trimmed 12.23k resistor, times the internal bandgap below 0.3V to shut down the LT8300. This pin has an reference, determines the output voltage (plus the effect accurate 1.223V threshold and can be used to program a of any non-unity transformer turns ratio). Minimize trace VIN undervoltage lockout (UVLO) threshold using a resis- area at this pin. tor divider from VIN to ground. A 2.5µA current hysteresis
SW (Pin 4):
Drain of the 150V Internal DMOS Power al ows the programming of VIN UVLO hysteresis. If neither Switch. Minimize trace area at this pin to reduce EMI and function is used, tie this pin directly to VIN. voltage spikes.
GND (Pin 2):
Ground. Tie this pin directly to local ground
V
plane.
IN (Pin 5):
Input Supply. The VIN pin supplies current to internal circuitry and serves as a reference voltage for
RFB (Pin 3):
Input Pin for External Feedback Resistor. the feedback circuitry connected to the RFB pin. Locally Connect a resistor from this pin to the transformer bypass this pin to ground with a capacitor.
BLOCK DIAGRAM
T1 DOUT VIN NPS:1 V + OUT • CIN LPRI LSEC COUT • RFB V – OUT 5 3 4 VIN RFB SW BOUNDARY DETECTOR 1:4 M3 M2 OSCILLATOR – – gm 25µA RREF + S 12.23kΩ 1.223V A3 R Q DRIVER M1 + R1 EN/UVLO – + 1 R A2 SENSE 2.5µA A1 0.3Ω R2 + – 1.223V VIN GND 2 M4 REFERENCE REGULATORS 8300 BD Rev. A 6 For more information www.analog.com Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Operation Applications Information Typical Applications Package Description Typical Application Related Parts