HIP6521(2000) Ver la hoja de datos (PDF) - Intersil

Número de pieza

componentes Descripción

Fabricante

HIP6521
(Rev.:2000)

PWM and Triple Linear Power Controller

Intersil 

HIP6521

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

2. The minimum IOCSET from the specification table.

3. Determine IPEAK for IPEAK > IOUT(MAX) + (∆I)/2, where

∆I is the output inductor ripple current.

OVERCURRENT TRIP:

VDS > VSET

iD × rDS(ON) > IOCSET × ROCSET

OCSET

VIN = +5V

ROCSET

OC

+

-

OCC

PWM

IOCSET

40µA

DRIVE

GATE

CONTROL

VSET +

VCC

UGATE

PHASE

iD

+

VDS(ON)

VPHASE = VIN – VDS

VOCSET = VIN – VSET

FIGURE 3. OVERCURRENT DETECTION

For an equation for the ripple current see the section under

component guidelines titled ‘Output Inductor Selection’.

Output Voltage Selection

The output voltage of the PWM converter can be resistor-

programmed to any level between VIN and 0.8V. However,

since the value of RS1 is affecting the values of the rest of

the compensation components, it is advisable its value is

kept between 2kΩ and 5kΩ.

3.3VIN

VOUT3

+

COUT3

Q4

DRIVE3

FB3

RS3

RP3

HIP6521

Q5

VOUT4

+

COUT4

DRIVE4

FB4

RS4

RP4

VOUT

=

0.8 ×







1

+

RR-----SP-- 

FIGURE 4. ADJUSTING THE OUTPUT VOLTAGE OF ANY OF

THE FOUR REGULATORS (OUTPUTS 3 AND 4

PICTURED)

All linear regulators’ output voltages are set by means of

external resistor dividers as shown in Figure 4. The two

resistors used to set the voltage on each of the three linear

regulators have to meet the following criteria: their value

while in a parallel connection has to be less than 5kΩ, or

otherwise said, the following relationship has to be met:

-RR----SS-----+×-----RR----P-P- < 5kΩ

There may be a second restriction on the size of the

resistors used to set the linear regulators’ output voltage

based on ACPI functionality. Read the ‘ACPI

Implementation’ section under ‘Application Guidelines’ to

see if this additional constraint concerns your application. To

ensure the parallel combination of the feedback resistors

equals a certain chosen value, RFB, use the following

equations:

RS

=

V-----O----U----T--

VFB

×

RFB

RP = V----R-O----SU----T-×----–-V----VF----BF---B-- , where

VOUT - the desired output voltage,

VFB - feedback (reference) voltage, 0.8V.

Application Guidelines

Soft-Start Interval

The soft-start function controls the output voltages rate of rise

to limit the current surge at start-up. The soft-start function is

integrated on the chip and the soft-start interval is thus fixed.

Layout Considerations

MOSFETs switch very fast and efficiently. The speed with

which the current transitions from one device to another

causes voltage spikes across the interconnecting

impedances and parasitic circuit elements. The voltage

spikes can degrade efficiency, radiate noise into the circuit,

and lead to device overvoltage stress. Careful component

layout and printed circuit design minimizes the voltage

spikes in the converter. Consider, as an example, the turn-

off transition of the upper PWM MOSFET. Prior to turn-off,

the upper MOSFET was carrying the full load current.

During the turn-off, current stops flowing in the upper

MOSFET and is picked up by the lower MOSFET or

Schottky diode. Any inductance in the switched current

path generates a large voltage spike during the switching

interval. Careful component selection, tight layout of the

critical components, and short, wide circuit traces minimize

the magnitude of voltage spikes. See the Application Note

AN9908 for evaluation board drawings of the component

placement and printed circuit board.

There are two sets of critical components in a DC-DC

converter using a HIP6521 controller. The switching power

components are the most critical because they switch large

amounts of energy, and as such, they tend to generate

7

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