PI3749 datasheet(16/26 Pages) VICOR

16 / 26 page

Cool-Power® ZVS Switching Regulators

Rev 1.6

vicorpower.com

Page 16 of 26

09/2016

800 927.9474

PI3749-x0

Overtemperature Protection

The internal package temperature is monitored to prevent

internal components from reaching their thermal maximum.

If the Overtemperature Protection threshold 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 decreases by more than the

Overtemperature Restart Hysteresis (TOTP_HYS).

Pulse Skip Mode (PSM)

PI3749-x0 features a hysteretic Pulse Skip Mode to achieve high

efficiency at light loads. The regulator is setup to skip pulses if

VEAO falls below the Pulse Skip Threshold (VEAO_PST). 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 Pulse Skip

Mode once the control node rises above the Pulse Skip Mode

threshold (VEAO_PST).

Variable Frequency Operation

The PI3749-x0 is preprogrammed to a fixed, maximum, base

operating frequency. The frequency is selected with respect to

the required power stage inductor to operate at peak efficiency

across line and load variations. The switching frequency period

will stretch as needed during each cycle to accommodate low

line and or high load conditions. By stretching the switching

frequency period, thus decreasing the switching frequency, the

ZVS operation is preserved throughout the input line voltage

range maintaining optimum efficiency.

IMON Amplifier

The PI3749-x0 provides a differential amplifier with a level

shifted, SGND referenced output, the IMON Pin, which is useful

for sensing input or output current on high voltage rails. A fixed

gain of 20:1 is provided over a large common mode range.

When using the amplifier, the ISN pin must be referenced to

the common mode voltage of the ISP pin for proper operation.

See Absolute Maximum Ratings for more information. If not in

use, the ISN and ISP pins should be connected to SGND and the

IMON pin left floating.

I2C Interface Operation

PI3749-20 devices provide an I2C digital interface that enables

the user to:

Device Configuration Options:

Dynamic VOUT margining

Programmable Sync Phase Delay

Fault telemetry including:

Input and Output Overvoltage

Input and Output Undervoltage

Internal Bias Supply Undervoltage

Overtemperature Protection

Multi Tiered Current Limit reporting

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