SC1933C datasheet(7/28 Pages) POWERINT

7 / 28 page

Rev. C 11/18

SC1933C/SC1936C

www.power.com

Figure 9. Cable Drop Compensation Characteristics.

Figure 10. Intelligent Quasi-Resonant Mode Switching.

PI-8035-072516

X × VFB

VFB

Onset of CC

Regulation

No-Load

Cable Drop

Compensation

Load Current

Output Voltage

Request Window

Time

FEEDBACK Pin Short Detection

If the sensed FEEDBACK pin voltage is below V

FB(OFF) at start-up, the

secondary controller will complete the handshake to take control of

the primary and complete t

SS(RAMP) and will stop requesting cycles to

initiate auto-restart (no cycle requests made to primary for longer

than t

AR(SK) second triggers auto-restart).

During normal operation, the secondary will stop requesting pulses

from the primary to initiate an auto-restart cycle when the FEEDBACK

pin voltage falls below the V

FB(OFF) threshold. The deglitch filter on the

protection mode is on for less than ~10 ms. By this mechanism, the

secondary will relinquish control after detecting that the FEEDBACK

pin is shorted to ground.

Cable Drop Compensation (CDC)

The amount of cable drop compensation is a function of the load with

respect to the constant current regulation threshold as illustrated in

Figure 9.

Auto-Restart Thresholds

The OUTPUT VOLTAGE pin includes a comparator to detect when the

output voltage falls below V

FB(AR) or VVOUT(AR), for a duration exceeding

FB(AR) or tVOUT(AR)respectively. The secondary controller will relinquish

control when this fault condition is detected. This threshold is meant

to limit the range of constant current (CC) operation and is included

to support high power charger applications.

SECONDARY BYPASS Pin Overvoltage Protection

The SC1933C/SC1936C secondary controller features a SECONDARY

BYPASS pin OV feature similar to the PRIMARY BYPASS pin OV feature.

When the secondary is in control, in the event that the SECONDARY

BYPASS pin current exceeds I

BPS(SD) (~7 mA) the secondary will send a

command to the primary to initiate an auto-restart off-time (t

AR(OFF)) or

latch-off (see Secondary Fault Response in Feature Code Addendum).

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