PI3740-00 datasheet(21/51 Pages) VICOR

21 / 51 page

Cool-Power® ZVS Switching Regulators

Rev 1.9

Page 21 of 51

06/2018

PI3740-00

Output Overvoltage Protection

The PI3740-00 is equipped with two methods of detecting

an output overvoltage condition. To prevent damage to input

voltage-sensitive devices, if the output voltage exceeds 20% of

its set regulated value as measured by the EAIN pin (VEAIN_OV),

the regulator will complete the current cycle, stop switching and

issue an OVP fault. Also if the output voltage of the regulator

exceeds the VOUT Overvoltage Threshold (VOUT_OVT) then 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 PI3740-00 features an overtemperature protection (OTP),

which will not engage until after the product is operated

above the maximum rated temperature. The OTP circuit is only

designed to protect against catastrophic failure due to excessive

temperatures and should not be relied upon to ensure the device

stays within the recommended operating temperature range.

Thermal shutdown terminates switching and discharges the

soft-start capacitor. As the temperature falls the PI3740-00 will

restart, and this will always occur before the product returns to

rated temperature range.

Pulse Skip Mode (PSM)

PI3740-00 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 PI3740-00 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 PI3740-00 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.

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