FPV1006-125-R datasheet(23/30 Pages) VICOR

23 / 30 page

Cool-Power®

Rev 1.3

vicorpower.com

Page 23 of 30

12/2015

800 927.9474

PI34xx-00

Figure 37 — PI34xx-00 parallel operation

SGND

VS1

PGND

REM

TRK

EAO

(#1)

SGND

VS1

PGND

REM

(#2)

EAO(#2)

TRK(#2)

EN(#2)

PGD

SYNCI

SYNCO

SYNCI(#2)

SYNCO(#2)

TRK

EAO

EAO(#1)

TRK(#1)

EN(#1)

PGD

SYNCI

SYNCO

SYNCI(#1)

SYNCO(#1)

OUT

ZVS Buck

Table 2 — PI34xx-00 family output voltage ranges

Device

Output Voltage

Set

Range

PI3420-00-LGIZ

1.0 V

1.0 to 1.4 V

PI3421-00-LGIZ

1.8 V

1.4 to 2.0 V

PI3422-00-LGIZ

2.5 V

2.0 to 3.1 V

PI3423-00-LGIZ

3.3 V

2.3 to 4.1 V

PI3424-00-LGIZ

5.0 V

3.3 to 6.5 V

Output Overvoltage Protection

The PI34xx-00 family is equipped with output Overvoltage

Protection (OVP) to prevent damage to input voltage

sensitive devices. If the output voltage exceeds 20% of its set

regulated value, the regulator will complete the current cycle,

stop switching and issue an OVP fault. The system will

resume operation once the output voltage falls below the

OVP threshold and after Fault Restart Delay.

Overtemperature Protection

The internal package temperature is monitored to prevent

internal components from reaching their thermal maximum.

If the Over Temperature Protection Threshold (OTP) is

exceeded (TOTP), the regulator will complete the current

switching cycle, enter a low power mode, set a fault flag, and

will soft-start when the internal temperature falls below Over-

Temperature Restart (TOTP_HYS).

Parallel Operation

Paralleling modules can be used to increase the output

current capability of a single power rail and reduce output

voltage ripple.

By connecting the EAO pins and SGND pins of each module

together the units will share the current equally. When the

TRK pins of each unit are connected together, the units will

track each other during soft-start and all unit EN pins have to

be released to allow the units to start (See Figure 37). Also,

any fault event in any regulator will disable the other

regulators. The two regulators will be out of phase with each

other reducing output ripple (refer to Switching Frequency

Synchronization).

To provide synchronization between regulators over the

entire operational frequency range, the Parallel Good (PGD)

pin must be connected to the lead regulator’s (#1) SYNCI pin

and a 2.5 kΩ Resistor, R1, must be placed between SYNCO

(#2) return and the lead regulator’s SYNCI (#1) pin, as shown

in Figure 37. In this configuration, at system soft-start, the

PGD pin pulls SYNCI low forcing the lead regulator to

initialize the open-loop startup synchronization. Once the

regulators reach regulation, SYNCI is released and the system

is now synchronized in a closed-loop configuration which

allows the system to adjust, on the fly, when any of the

individual regulators begin to enter variable frequency mode

in the loop.

Pulse Skip Mode (PSM)

PI34xx-00 features a PSM to achieve high efficiency at light

loads. The regulators are setup to skip pulses if EAO falls

below a PSM threshold. Depending on conditions and

component values, this may result in single pulses or several

consecutive pulses followed by skipped pulses. Skipping

cycles significantly reduces gate drive power and improves

light load efficiency. The regulator will leave PSM once the

EAO rises above the Skip Mode threshold.

Variable Frequency Operation

Each PI34xx-00 is preprogrammed to a base operating

frequency, with respect to the power stage inductor (see

Table 4), to operate at peak efficiency across line and load

variations. At low line and high load applications, the base

frequency will decrease to accommodate these extreme

operating ranges. By stretching the frequency, the ZVS

operation is preserved throughout the total input line voltage

range therefore maintaining optimum efficiency.

Application Description

Output Voltage Trim

The PI34xx-00 family of Buck Regulators provides five

common output voltages: 1.0 V, 1.8 V, 2.5 V, 3.3 V and 5.0 V. A

post-package trim step is implemented to offset any resistor

divider network errors ensuring maximum output accuracy.

With a single resistor connected from the ADJ pin to SGND or

REM, each device’s output can be varied above or below the

nominal set voltage (the PI3420-00 can only be adjusted

above the set voltage of 1 V).

The remote pin (REM) should always be connected to the

VOUT pin to prevent an output voltage offset. Figure 38 shows

the internal feedback voltage divider network.

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