ISL68236IRAZ datasheet(30/107 Pages) RENESAS

30 / 107 page

ISL68225, ISL68236

6. Fault Monitoring and Protection

R16DS0047EU0100 Rev.1.00

Page 30 of 106

Oct.1.20

6.3

Output Overcurrent Protection

The ISL68225 and ISL68236 provide a comprehensive overcurrent protection scheme that monitors the total

output current, peak phase current, and the valley phase current. The scheme allows you to eliminate inductor

saturation and limit the total output current. The ISL68225 and ISL68236 support shutdown and retry response

types for OC faults. The response configuration applies to all output current fault mechanisms such as phase

peak overcurrent and total output overcurrent.

Figure 21 shows the block diagram of the output overcurrent protection scheme.

Phases are protected from both overcurrent and undercurrent using a pulse-by-pulse scheme that acts instantly

on a PWM signal if a detected phase current reaches its threshold. Thresholds for overcurrent and undercurrent

allow you to precisely limit phase currents so the inductors never saturate. Phase current limiting behavior can be

configured to either shut down the device after a user-determined number of consecutive events or continue

indefinitely. If configured to continue indefinitely, the converter behaves much like a current source. Figures 22

and 23 show per-phase current limiting when the device is configured to shut down after a user-determined

number of consecutive events.

In addition to phase based current limiting, the ISL68225 and ISL68236 support total output current limits that

have user-adjustable response delay. The two sum current limits, fast and slow, allow you to permit high

maximum output current for a shorter period of time and lower output current for a longer period. The response

delay for the limiting mechanisms is also adjustable. These mechanisms do not restrict the maximum output

current until the current has exceeded a threshold for the response delay time. For example, suppose the device

is configured with a Fast Sum OC limit of 250A, a response delay of 50µs, and a shutdown response type. Next,

suppose a 300A load is placed on the regulator. 300A is supplied to the load for 50µs, and the device shuts down

as shown in Figure 24 on page 31.

Figure 21. OCP Functional Diagram

Figure 22. Peak OC Operation

Figure 23. Peak UC Operation

ISL68236IRAZ Datasheet(PDF) 30 Page - Renesas Technology Corp