ISL8200AMMREP datasheet(17/24 Pages) RENESAS

17 / 24 page

ISL8200AMM

FN8287 Rev 2.00

Page 17 of 24

June 3, 2015

shown in these graphs is the average output current and not the

inductor ripple current.

In a high input voltage, high output voltage application, such as

20V input to 5V output, the inductor ripple becomes excessive

due to the fixed internal inductor value. In such applications, the

output current will be limited from the rating to approximately

70% of the module’s rated current.

When OCP is triggered, the controller pulls EN low immediately to

turn off UGATE and LGATE.

For overload and hard short conditions, the overcurrent

protection reduces the regulator RMS output current much less

than full load by putting the controller into hiccup mode. A delay

time, equal to 3 soft-start intervals, is entered to allow the

disturbance to be cleared out. After the delay time, the controller

then initiates a soft-start interval. If the output voltage comes up

and returns to the regulation, PGOOD transitions high. If the OC

trip is exceeded during the soft-start interval, the controller pulls

EN low again. The PGOOD signal will remain low and the

soft-start interval will be allowed to expire. Another soft-start

interval will be initiated after the delay interval. If an overcurrent

trip occurs again, this same cycle repeats until the fault is

removed.

Fault Handshake

In a multi-module system, with the EN pins wired OR’ed together,

all modules can immediately turn off, at one time, when a fault

condition occurs in one or more modules. A fault would pull the

EN pin low, disabling all the modules and therefore not creating

current bounce. Thus, no single channel would be over stressed

when a fault occurs.

Since the EN pins are pulled down under fault conditions, the

pull-up resistor (RUP) should be scaled to sink no more than 5mA

current from EN pin. Essentially, the EN pins cannot be directly

connected to VCC.

Oscillator

The Oscillator is a sawtooth waveform, providing for leading edge

modulation with 350ns minimum dead time. The oscillator

(sawtooth) waveform has a DC offset of 1.0V. Each channel’s

peak-to-peak of the ramp amplitude is set to be proportional to

the voltage applied to its corresponding FF pin.

FIGURE 31. 5VIN

FIGURE 32. 12VIN

VIN

PVIN

VOUT

VOUT_SET

PHASE

OCSET

ISL8200AMMREP

POWER MODULE

ISHARE

VIN = 4.5V TO 20V



FIGURE 30. ISL8200AMMREP USING RISEN-EX BETWEEN

OCSET and PHASE

1.8VOUT

1.2VOUT

2.5VOUT

RISEN-EX(kΩ)

RISEN-EX (kΩ)

1020

3040

1.8VOUT

2.5VOUT

1.2VOUT

5.0VOUT

FIGURE 33. 20VIN

RISEN-EX (kΩ)

020

100

1.8VOUT

2.5VOUT

1.2VOUT

5.0VOUT

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