HIP6015CB datasheet(6/12 Pages) INTERSIL

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Over-Current Protection

The over-current function protects the converter from a

shorted output by using the upper MOSFET’s on-resistance,

rDS(ON) to monitor the current. This method enhances the

converter’s efﬁciency and reduces cost by eliminating a

current sensing resistor.

The over-current function cycles the soft-start function in a

hiccup mode to provide fault protection. A resistor (ROCSET)

programs the over-current trip level. An internal 200

µA current

sink develops a voltage across ROCSET that is referenced to

VIN. When the voltage across the upper MOSFET (also

referenced to VIN) exceeds the voltage across ROCSET, the

over-current function initiates a soft-start sequence. The soft-

start function discharges CSS with a 10µA current sink and

inhibits PWM operation. The soft-start function recharges

CSS, and PWM operation resumes with the error amplifier

clamped to the SS voltage. Should an overload occur while

recharging CSS, the soft start function inhibits PWM operation

while fully charging CSS to 4V to complete its cycle. Figure 4

shows this operation with an overload condition. Note that the

inductor current increases to over 15A during the CSS

charging interval and causes an over-current trip. The

converter dissipates very little power with this method. The

measured input power for the conditions of Figure 4 is 2.5W.

The over-current function will trip at a peak inductor current

(IPEAK) determined by:

where IOCSET is the internal OCSET current source (200µA

typical). The OC trip point varies mainly due to the

MOSFET’s rDS(ON) variations. To avoid over-current tripping

in the normal operating load range, ﬁnd the ROCSET resistor

from the equation above with:

1. The maximum rDS(ON) at the highest junction temperature.

2. The minimum IOCSET from the speciﬁcation table.

3. Determine IPEAK for

where

∆I is the output inductor ripple current.

For an equation for the ripple current see the section under

component guidelines titled “Output Inductor Selection.”

A small ceramic capacitor should be placed in parallel with

ROCSET to smooth the voltage across ROCSET in the

presence of switching noise on the input voltage.

TIME (20ms/DIV.)

10A

15A

FIGURE 4. OVER-CURRENT OPERATION

PEAK

OCSET

•

DS ON

()

---------------------------------------------------

PEAK

OUT MAX

()

∆I

() 2

⁄

TABLE 1. OUTPUT VOLTAGE PROGRAM

PIN NAME

NOMINAL OUTPUT

VOLTAGE DACOUT

PIN NAME

NOMINAL OUTPUT

VOLTAGE DACOUT

VID4

VID3

VID2

VID1

VID0

VID4

VID3

VID2

VID1

VID0

01111

11111

01110

11110

2.1

01101

11101

2.2

01100

11100

2.3

01011

11011

2.4

01010

11010

2.5

01001

11001

2.6

01000

11000

2.7

00111

10111

2.8

00110

10110

2.9

00101

1.80

10101

3.0

00100

1.85

10100

3.1

00011

1.90

10011

3.2

00010

1.95

10010

3.3

00001

2.00

10001

3.4

00000

2.05

10000

3.5

NOTE: 0 = connected to GND or VSS, 1 = connected to VDD through pull-up resistors.

HIP6015

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