IR3521 datasheet(26/45 Pages) IRF

26 / 45 page

IR3521

Page 26

V3.03

Open Remote Sense Line Protection

If either remote sense line VOSENX+ or VOSENX- is open, the output of Remote Sense Amplifier (VOUTX) drops.

The IR3521 continuously monitors the VOUTX pin and if VOUTX is lower than 200 mV, two separate pulse currents

are applied to the VOSENX+ and VOSENX- pins to check if the sense lines are open. If VOSENX+ is open, a voltage

higher than 90% of V(VCCL) will be present at VOSENX+ pin and the output of Open Line Detect Comparator will

be high. If VOSENX- is open, a voltage higher than 400mV will be present at VOSENX- pin and the Open Line

Detect Comparator output will be high. With either sense line open, the Open Sense Line Fault Latch will be set to

force the error amplifier output low and immediately shut down the converter. SS/DELX will be discharged and the

Open Sense Fault Latch can only be reset by cycling the power to VCCL.

Open Daisy Chain Protection

The IR3521 checks the daisy chain every time it powers up. It starts a daisy chain pulse on the PHSOUT pin and

detects the feedback at PHSIN pin. If no pulse comes back after 32 CLKOUT pulses, the pulse is restarted again. If

the pulse fails to come back the second time, the Open Daisy Chain fault is registered, and SS/DELX is not allowed

to charge. The fault latch can only be reset by cycling the power to VCCL.

After powering up, the IR3521 monitors PHSIN pin for a phase input pulse equal or less than the number of phases

detected. If PHSIN pulse does not return within the number of phases in the converter, another pulse is started on

PHSOUT pin. If the second started PHSOUT pulse does not return on PHSIN, an Open Daisy Chain fault is

registered.

Phase Number Determination

After a daisy chain pulse is started, the IR3521 checks the timing of the input pulse at PHSIN pin to determine the

phase number.

IR3521 Datasheet(PDF) 26 Page - International Rectifier