IR3622MPBF Ver la hoja de datos (PDF) - International Rectifier

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IR3622MPBF

HIGH FREQUENCY 2-PHASE, SINGLE OR DUAL OUTPUT SYNCHRONOUS STEP DOWN CONTROLLER WITH OUTPUT TRACKING AND SEQUENCING

International Rectifier 

IR3622MPbF

Internal Regulator

The IR3622 features an on-board 7.2V regulator

with short circuit protection. The regulator is

capable of sourcing current up to 100mA. This

integrated regulator can be used to generate the

necessary bias voltage for drivers, an example of

how this can be used is shown in figure 23,

page26.

Out-of-Phase Operation

The IR3622 drives its two output stages 180o out-

of-phase. In current share mode single output,

the two inductor ripple currents cancel each other

and result in a reduction of the output current

ripple and yield a smaller output capacitor for the

same voltage ripple requirement. Figure 4 shows

two channels inductor current and the resulting

voltage ripple at the output.

HDRV1

0

HDRV2

DT

T

IL1

IL2

Ic

Io

Fig. 4: Current ripple cancellation for output

In addition, the 180o out of phase contributes to

input current cancellation. This results in much

smaller input capacitor’s RMS current and

reduces the number of required input capacitors.

Figure 5 shows the equivalent RMS current.

Single Phase

2 Phase

Duty Cycle (Vo/Vin)

Fig. 5: Input RMS value vs. Duty Cycle

Mode Selection

The IR3622 can operate as a dual output

independently regulated buck converter, or as a

2 phase single output buck converter (current

share mode). The SS2 pin is used for mode

selection. In current share mode this pin should

be floating. In the dual output mode, a soft start

capacitor must be connected from this pin to the

ground to program the start time for the second

output.

Independent Mode

In this mode the IR3622 provides control to two

independent output power supplies with either

common or different input voltages. The output

voltage of each individual channel is set and

controlled by the output of the error amplifier,

which is the amplified error signal from the

sensed output voltage and the reference voltage.

The error amplifier output voltage is compared to

the ramp signal thus generating fixed frequency

pulses of variable duty-cycle, (PWM) which are

applied to the internal MOSEFT drivers. Figure

24 shows a typical schematic for such

application.

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