FDMF3170 datasheet(18/21 Pages) ONSEMI

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FDMF3170

Rev. 1.2

Over-Temperature Protection (OTP)

An over-temperature event is considered catastrophic in

nature. OTP raises fault flag HIGH once TMON

exceeds 140°C temperature. Driver still responds to

PWM commands (NO tri-state shutdown). Once TMON

falls below 125°C, fault flag is cleared internally by

driver IC.

Over-Current Protection (OCP)

The

FDMF3170

has

cycle-by-cycle

over

current

protection. If current exceeds the OCP threshold, HS

FET is gated off regardless of PWM command. HS FET

cannot be gated on again until the current is less than

the OCP threshold with a hysteresis.

Fault flag will be pulled HIGH after 10 cycle-by-cycle

OCPs are detected without 3 consecutive normal cycle

occurring. Fault flag will clear once 3 consecutive cycle

of OCP is NOT detected. Module never shuts down (nor

does it disable HDRV/LDRV outputs

– i.e., enter

internal

tri-state)

and

always

responds

PWM

commands (but driver will still truncate HS on time

when PWM=HIGH and ILIM is detected).

High-Side MOSFET Short Fault

A high-side MOSFET short fault feature is added to the

FDMF3170. If a high-side MOSFET short fault is

detected, the driver will pull the TMON / FAULT pin

HIGH and continue to respond to PWM commands.

Fault flag will clear once HS short is NOT detected or

5 Vcc power re-cycle, EN toggle.

Pre-OVP

The FDMF3170 SPS module monitors VOUT during the

power up period. If an abnormally high VOUT is detected

during this time, the SPS will gate

–on the LS FET until

the FAULT clears.

Negative-OCP

The FDMF3170 can detect large negative inductor

current and protect the low side MOSFET. Once this

negative current threshold is detected, FDMF3170

takes control and truncates LS on-time pulse (LS FET is

gated off regardless of PWM command). Driver will

return to responding to PWM commands once inductor

current falls to -40 A. So, if PWM is still being

commanded LOW by controller when inductor falls to -

40 A, then LS FET will turn back on. SPS will enter a

current limiting (hiccup) mode regulating inductor

current from -40 A to -60 A until inductor current

relaxes.

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