SC1933C datasheet(3/28 Pages) POWERINT

3 / 28 page

Rev. C 11/18

SC1933C/SC1936C

www.power.com

Figure 5. Pin Configuration.

V 13

12 NC

BPP 14

11 NC

NC 15

10 NC

9 NC

S 16-19

D 24

8 NC

7 FWD

6 VOUT

5 SR

4 BPS

3 FB

2 GND

1 IS

PI-7877-022216

Pin Functional Description

ISENSE (IS) Pin (Pin 1)

Connection to the power supply output terminals. An external

current sense resistor should be connected between this and the

GND pin. If current regulation is not required, this pin should be tied

to the GND pin.

SECONDARY GROUND (GND) (Pin 2)

GND for the secondary IC. Note this is not the power supply output

GND due to the presence of the sense resistor between this and the

ISENSE pin.

FEEDBACK (FB) Pin (Pin 3)

Connection to an external resistor divider to set the power supply

output voltage.

SECONDARY BYPASS (BPS) Pin (Pin 4)

Connection point for an external bypass capacitor for the secondary

IC supply.

SYNCHRONOUS RECTIFIER DRIVE (SR) Pin (Pin 5)

Gate driver for external SR FET. If no SR FET is used connect this pin

to GND.

OUTPUT VOLTAGE (VOUT) Pin (Pin 6)

Connected directly to the output voltage, to provide current for the

controller on the secondary-side and provide secondary protection.

FORWARD (FWD) Pin (Pin 7)

The connection point to the switching node of the transformer output

winding providing information on primary switch timing. Provides power

for the secondary-side controller when V

OUT is below threshold.

NC Pin (Pin 8-12)

Leave open. Should not be connected to any other pins.

UNDER/OVER INPUT VOLTAGE (V) Pin (Pin 13)

A high-voltage pin connected to the AC or DC side of the input bridge

for detecting undervoltage and overvoltage conditions at the power

supply input. This pin should be tied to GND to disable UV/OV

protection.

PRIMARY BYPASS (BPP) Pin (Pin 14)

The connection point for an external bypass capacitor for the

primary-side supply. This is also the ILIM selection pin for choosing

standard ILIM or ILIM+1.

NC Pin (Pin 15)

Leave open. Should not be connected to any other pins.

SOURCE (S) Pin (Pin 16-19)

These pins are the power switch source connection. Also ground

reference for primary BYPASS pin.

DRAIN (D) Pin (Pin 24)

Power switch drain connection.

Functional Description

The SC1933C/SC1936C combines a high-voltage power switch, along

with both primary-side and secondary-side controllers in one device.

The architecture incorporates a novel inductive coupling feedback

scheme (FluxLink) using the package lead frame and bond wires to

provide a safe, reliable, and cost-effective means to transmit

accurate, output voltage and current information from the secondary

controller to the primary controller.

The primary controller on SC1933C/SC1936C is a Quasi-Resonant

(QR) flyback controller that has the ability to operate in continuous

conduction mode (CCM), boundary mode (CrM) and discontinuous

conduction mode (DCM). The controller uses both variable frequency

and variable current control schemes. The primary controller consists

of a frequency jitter oscillator, a receiver circuit magnetically coupled to

the secondary controller, a current limit controller, 5 V regulator on

the PRIMARY BYPASS pin, audible noise reduction engine for light

load operation, bypass overvoltage detection circuit, a lossless input

line sensing circuit, current limit selection circuitry, over-temperature

protection, leading edge blanking, secondary output diode / SR FET

short protection circuit and a power switch.

The SC1933C/SC1936C secondary controller consists of a transmitter

circuit that is magnetically coupled to the primary receiver, a constant

voltage (CV) and a constant current (CC) control circuit, a 4.4 V

regulator on the SECONDARY BYPASS pin, synchronous rectifier FET

driver, QR mode circuit, oscillator and timing circuit, and numerous

integrated protection features.

Figure 3 and Figure 4 show the functional block diagrams of the

primary and secondary controller, highlighting the most important

features.

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