NB650/NB650H

– 6A, 28V, FAST-TRANSIENT, SYNCHRONOUS STEP-DOWN CONVERTERS

NB650/NB650H Rev. 1.13

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13

10/7/2019

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Preliminary Specifications Subject to Change

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on the output and triggers OCP immediately. This

is short circuit protection (SCP).

Under OCP/SCP condition, NB650 will latch off.

The converter needs power cycle to restart.

NB650H will try to recover from OCP/SCP fault

with hiccup mode. That means in OCP/SCP

protection, the NB650H will disable the output

power stage, discharge soft-start capacitor and

then automatically try to start again. If the over-

current condition still holds after soft-start ends,

the NB650H repeats this operation cycle till over-

current fault is removed and output rises back to

regulation level.

Over/Under-Voltage Protection

The NB650/NB650H monitors the output voltage

through the FB voltage to detect overvoltage and

under voltage on the output. When the FB

voltage

exceeds

0.8V,

the

over-voltage

protection (OVP) triggers. Once OVP triggers,

the LS-FET is always on while the HS-FET is

always off. The device needs to power cycle to

power up again. Under-voltage protection (UVP)

triggers when the FB voltage is below 0.4V.

Usually, UVP accompanies hitting the current

limit, which results in SCP.

UVLO Protection

The NB650/NB650H has under-voltage lockout

(UVLO) protection. When VIN exceeds the UVLO-

rising threshold voltage, the NB650/NB650H

powers up. It shuts off when VIN falls below the

UVLO-falling threshold voltage. This is non-latch

protection.

Thermal Shutdown

The NB650/NB650H employs thermal shutdown

by internally monitoring the temperature of the

junction. If the junction temperature exceeds the

threshold value (typically 150°C), the converter

shuts off. This is non-latch protection. There is

about

25°C

hysteresis.

Once

the

junction

temperature drops to around 125°C, it initiates a

soft-start.