MP3363

– SINGLE-STRING, 1.8V MINIMUM VIN, 36 VOUT BOOST LED DRIVER

MP3363 Rev. 1.0

MonolithicPower.com

10

9/28/2021

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© 2021 MPS. All Rights Reserved.



FB

LED

FB

V

I

Duty

R

(1)

Where VFB is about 200mV, RFB is the feedback

resistor, and Duty is the PWM signal duty.

Protections

The

MP3363

’s protection features include

UVLO, OVP, OCP, short load protection, short

FB to GND protection, and TSD.

Under-Voltage Lockout (UVLO)

The MP3363 integrates VIN UVLO protection.

The internal circuit does not work until VIN

reaches the UVLO rising threshold.

Over-Voltage Protection (OVP)

Over-voltage (OV) conditions are detected by

sensing the OVP pin

’s voltage. If the OVP pin’s

voltage reaches its high threshold, OVP is

triggered and the IC stops switching. The IC

tries to recover once the OVP

pin’s voltage

drops to its low threshold.

Short Load Protection

Under short load conditions, a large short

current is detected by the FB sense resistor. If

the FB-sensed voltage exceeds 600mV for 20

switching

cycles,

short

load

protection

is

triggered and the IC stops switching. The IC

resumes switching once the short condition

disappears.

High voltage appears on the FB pin under short

load conditions. Figure 3 shows the additional

components that are required to protect the FB

pin from damage. If a short occurs, a diode (D1)

can be used to clamp VFB to about 0.3V. A

Zener diode can also be used to clamp VFB.

FB

D1

RFB

FB

D1

RFB

R1

a) Standard Diode

b) Zener Diode

Figure 3: Short Load Protection for the FB Pin

Note that there is a short loop from the input to

GND under short load conditions. Use a fuse or

an external circuit to cut off the short loop.

OVP Pin Under-Voltage Protection (UVP)

If the OVP pin’s voltage drops below 50mV for

10µs during normal operation, UVP is triggered

and the IC stops switching. This protection is

blanked during soft start.

Over-Current

Protection

(OCP)

(Short

Inductor/Diode Protection)

If there is an inductor or diode short and the

MOSFET's current exceeds the latch-off current

limit (typically 2.5A) for seven consecutive

cycles, then OCP is triggered and the IC stops

switching. Once the short disappears, the IC

resumes normal operation.

Short FB to GND Protection

If VFB drops below 50mV and the COMP

saturation lasts for 20ms, the IC stops switching.

Once the short disappears, the IC resumes

normal operation.

Thermal Shutdown

Thermal shutdown prevents the MP3363 from

operating at exceedingly high temperatures. If

the

die

temperature

exceeds

the

upper

threshold (TSD = 170°C), the COMP pin is pulled

low. The IC resumes normal operation when

the die temperature drops below the lower

threshold. The hysteresis is about 20°C.