ISL6520AIBZ-T Datasheet ISL6520ACBZ, ISL6520ACBZ-T, ISL6520ACBZA | P4-P6

FN9016.6

December 10, 2009

Absolute Maximum Ratings Thermal Information

Supply Voltage, V

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +6.0V

Absolute Boot Voltage, V

BOOT

. . . . . . . . . . . . . . . . . . . . . . . +15.0V

Upper Driver Supply Voltage, V

BOOT

- V

PHASE

. . . . . . . . 7.0V (DC)

. . . . . . . . . . . . . . . . . . . . . . . . . . 8.0V (<10ns Pulse Width, 10μJ)

Input, Output or I/O Voltage . . . . . . . . . . . GND -0.3V to VCC +0.3V

ESD Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Class 2

Operating Conditions

Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . +5V ±10%

Ambient Temperature Range - ISL6520AC . . . . . . . . . 0°C to +70°C

Ambient Temperature Range - ISL6520AI. . . . . . . . .-40°C to +85°C

Junction Temperature Range. . . . . . . . . . . . . . . . . .-40°C to +125°C

Thermal Resistance θ

(°C/W) θ

(°C/W)

SOIC Package (Note 1) . . . . . . . . . . . . . . 95 N/A

QFN Package (Notes 2, 3). . . . . . . . . . . . . 45 7

Maximum Junction Temperature (Plastic Package). . . . . . . . +150°C

Maximum Storage Temperature Range. . . . . . . . . .-65°C to +150°C

Pb-Free Reflow Profile. . . . . . . . . . . . . . . . . . . . . . . . .see link below

http://www.intersil.com/pbfree/Pb-FreeReflow.asp

CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product reliability and

result in failures not covered by warranty.

NOTES:

1. θ

is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.

2. θ

is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See

Tech Brief TB379.

3. For θ

, the “case temp” location is the center of the exposed metal pad on the package underside.

Electrical Specifications Recommended Operating Conditions, Unless Otherwise Noted.

PARAMETER SYMBOL TEST CONDITIONS

MIN

(Note 4) TYP

MAX

(Note 4) UNITS

VCC SUPPLY CURRENT

Nominal Supply I

VCC

2.6 3.2 3.8 mA

POWER-ON RESET

Rising VCC POR Threshold POR 4.19 4.30 4.50 V

VCC POR Threshold Hysteresis -0.25- V

OSCILLATOR

Frequency f

OSC

ISL6520AC, VCC

= 5V 250 300 340 kHz

ISL6520AI, VCC

= 5V 230 300 340 kHz

Ramp Amplitude DV

OSC

-1.5-V

P-P

REFERENCE

Reference Voltage Tolerance ISL6520AC -1.5 - +1.5 %

ISL6520AI -2.5 - +2.5 %

Nominal Reference Voltage V

REF

-0.800- V

ERROR AMPLIFIER

DC Gain Limits established by characterization and

are not production tested

-88- dB

Gain-Bandwidth Product GBWP - 15 - MHz

Slew Rate SR - 8 - V/µs

GATE DRIVERS

Upper Gate Source Current I

UGATE-SRC

BOOT

- V

PHASE

= 5V, V

UGATE

= 4V - -1 - A

Upper Gate Sink Current I

UGATE-SNK

-1- A

Lower Gate Source Current I

LGATE-SRC

VCC

= 5V, V

LGATE

= 4V - -1 - A

Lower Gate Sink Current I

LGATE-SNK

-2- A

PROTECTION / DISABLE

OCSET Current Source I

OCSET

ISL6520AC 17 20 22 µA

ISL6520AI 14 20 24 µA

Disable Threshold V

DISABLE

-0.8- V

NOTE:

4. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless otherwise specified. Temperature limits established by characterization

and are not production tested.

ISL6520A

FN9016.6

December 10, 2009

Functional Pin Description

VCC

This pin provides the bias supply for the ISL6520A, as well

as the lower MOSFET’s gate. Connect a well-decoupled 5V

supply to this pin.

This pin is the inverting input of the internal error amplifier.

Use this pin, in combination with the COMP/OCSET pin, to

compensate the voltage-control feedback loop of the

converter.

GND

This pin represents the signal and power ground for the IC.

Tie this pin to the ground island/plane through the lowest

impedance connection available.

PHASE

Connect this pin to the upper MOSFET’s source. This pin is

used to monitor the voltage drop across the upper MOSFET

for overcurrent protection.

UGATE

Connect this pin to the upper MOSFET’s gate. This pin

provides the PWM-controlled gate drive for the upper

MOSFET. This pin is also monitored by the adaptive

shoot-through protection circuitry to determine when the

upper MOSFET has turned off.

BOOT

This pin provides ground referenced bias voltage to the

upper MOSFET driver. A bootstrap circuit is used to create a

voltage suitable to drive a logic-level N-channel MOSFET.

COMP/OCSET

This is a multiplexed pin. During a short period of time

following power-on reset (POR), this pin is used to determine

the overcurrent threshold of the converter. Connect a

resistor (R

OCSET

) from this pin to the drain of the upper

MOSFET (V

). R

OCSET

, an internal 20µA current source

OCSET

), and the upper MOSFET on-resistance (r

DS(ON)

)

set the converter overcurrent (OC) trip point according to

Equation 1:

Internal circuitry of the ISL6520A will not recognize a voltage

drop across R

OCSET

larger than 0.5V. Any voltage drop

across R

OCSET

that is greater than 0.5V will set the

overcurrent trip point to:

An overcurrent trip cycles the soft-start function.

During soft-start, and all the time during normal converter

operation, this pin represents the output of the error

amplifier. Use this pin, in combination with the

COMP/OCSET pin, to compensate the voltage-control

feedback loop of the converter.

Pulling COMP/OCSET to a level below 0.8V disables the

controller. Disabling the ISL6520A causes the oscillator to

stop, the LGATE and UGATE outputs to be held low, and the

softstart circuitry to re-arm.

LGATE

Connect this pin to the lower MOSFET’s gate. This pin

provides the PWM-controlled gate drive for the lower

MOSFET. This pin is also monitored by the adaptive

shoot-through protection circuitry to determine when the

lower MOSFET has turned off.

Functional Description

Initialization

The ISL6520A automatically initializes upon receipt of power.

The Power-On Reset (POR) function continually monitors the

bias voltage at the VCC pin. The POR function initiates the

Overcurrent Protection (OCP) sampling and hold operation

after the supply voltage exceeds its POR threshold. Upon

completion of the OCP sampling and hold operation, the POR

function initiates the soft-start operation.

Overcurrent Protection

The overcurrent function protects the converter from a shorted

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

DS(ON)

to monitor the current. This method enhances the converter’s

efficiency and reduces cost by eliminating a current sensing

resistor.

The overcurrent function cycles the soft-start function in a

hiccup mode to provide fault protection. A resistor (R

OCSET

)

programs the overcurrent trip level (see “Typical Application”

on page 3).

Immediately following POR, the ISL6520A initiates the

Overcurrent Protection sampling and hold operation. First,

the internal error amplifier is disabled. This allows an internal

20mA current sink to develop a voltage across R

OCSET

. The

ISL6520A then samples this voltage at the COMP pin. This

sampled voltage, which is referenced to the VCC pin, is held

internally as the Overcurrent Set Point.

When the voltage across the upper MOSFET, which is also

referenced to the VCC pin, exceeds the Overcurrent Set

Point, the overcurrent function initiates a soft-start sequence.

Figure 1 shows the inductor current after a fault is introduced

while running at 15A. The continuous fault causes the

ISL6520A to go into a hiccup mode with a typical period of

25ms. The inductor current increases to 18A during the soft-

start interval and causes an overcurrent trip. The converter

dissipates very little power with this method. The measured

input power for the conditions of Figure 1 is only 1.5W.

PEAK

OCSET

DS ON()

-------------------------------------------------=

(EQ. 1)

PEAK

0.5V

DS ON()

----------------------=

(EQ. 2)

ISL6520A

FN9016.6

December 10, 2009

The overcurrent function will trip at a peak inductor current

PEAK)

determined by Equation 3:

where I

OCSET

is the internal OCSET current source (20µA

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

MOSFET’s r

DS(ON)

variations. To avoid overcurrent tripping

in the normal operating load range, find the R

OCSET

resistor

from the equation above with:

1. The maximum r

DS(ON)

at the highest junction

temperature.

2. The minimum I

OCSET

from the specification table.

3. Determine I

PEAK

for

where ΔI is the output inductor ripple current.

For an equation for the ripple current see the section under

component guidelines titled “Output Inductor Selection” on

page 8.

Soft-Start

The POR function initiates the soft-start sequence after the

overcurrent set point has been sampled. Soft-start clamps the

error amplifier output (COMP pin) and reference input

(non-inverting terminal of the error amp) to the internally

generated soft-start voltage. Figure 2 shows a typical start-up

interval where the COMP/OCSET pin has been released from

a grounded (system shutdown) state. Initially, the

COMP/OCSET is used to sample the overcurrent setpoint by

disabling the error amplifier and drawing 20µA through

OCSET

. Once the overcurrent level has been sampled, the

soft-start function is initiated. The clamp on the error amplifier

(COMP/OCSET pin) initially controls the converter’s output

voltage during soft-start. The oscillator’s triangular waveform is

compared to the ramping error amplifier voltage. This

generates PHASE pulses of increasing width that charge the

output capacitor(s). When the internally generated soft-start

voltage exceeds the feedback (FB pin) voltage, the output

voltage is in regulation. This method provides a rapid and

controlled output voltage rise. The entire startup sequence

typically take about 11ms.

Current Sinking

The ISL6520A incorporates a MOSFET shoot-through

protection method which allows a converter to sink current

as well as source current. Care should be exercised when

designing a converter with the ISL6520A when it is known

that the converter may sink current.

When the converter is sinking current, it is behaving as a

boost converter that is regulating it’s input voltage. This

means that the converter is boosting current into the V

rail, which supplies the bias voltage to the ISL6520A. If there

is nowhere for this current to go, such as to other distributed

loads on the V

rail, through a voltage limiting protection

device, or other methods, the capacitance on the V

bus

will absorb the current. This situation will allow voltage level

of the V

rail to increase. If the voltage level of the rail is

boosted to a level that exceeds the maximum voltage rating

of the ISL6520A, then the IC will experience an irreversible

failure and the converter will no longer be operational.

Ensuring that there is a path for the current to follow other

than the capacitance on the rail will prevent this failure

mode.

Application Guidelines

Layout Considerations

As in any high frequency switching converter, layout is very

important. Switching current from one power device to another

can generate voltage transients across the impedances of the

interconnecting bond wires and circuit traces. These

interconnecting impedances should be minimized by using

wide, short printed circuit traces. The critical components

should be located as close together as possible, using ground

plane construction or single point grounding.

FIGURE 1. OVERCURRENT OPERATION

TIME (5ms/DIV.)

OUTPUT

INDUCTOR

5A/DIV.

CURRENT

PEAK

OCSET

x R

OCSET

DS ON()

-----------------------------------------------------=

(EQ. 3)

PEAK

OUT MAX()

ΔI()

----------

FIGURE 2. SOFT-START INTERVAL

OUT

500mV/DIV.

COMP/OCSET

1V/DIV.

TIME (2ms/DIV.)

ISL6520A

P1-P3 P4-P6 P7-P9 P10-P12

ISL6520AIBZ-T

Mfr. #:

Buy ISL6520AIBZ-T

Manufacturer:

Renesas / Intersil

Description:

Switching Controllers C4M SINGLE 5V PWM CNTRLR W/DDRG

Lifecycle:

New from this manufacturer.

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ISL6520AIBZ-T

ISL6520AIBZ-T

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