MPQ3364

– 4-CH BOOST WLED DRIVER WITH HIGH DIM RATIO AND I2C, AEC-Q100

MPQ3364 Rev. 1.1

MonolithicPower.com

21

7/7/2021

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© 2021 MPS. All Rights Reserved.

APPLICATION INFORMATION

LED Current Setting

The LED current amplitude is set by an external

resistor connected from ISET to GND. The LED

current

amplitude

can

be

calculated

with

Equation (4):





LED

ISET

1245

I

(mA)

R

(k )

(4)

For example, if RISET = 24.9kΩ, the LED current

is 50mA.

Switching Frequency

The switching frequency can be configured by a

resistor, I2C interface, or external clock.

Configure the frequency by connecting an

external resistor to FREQ/SYNC. The switching

frequency can be estimated with Equation (5):





SW

OSC

22000

f (kHz)

R

(k )

(5)

For example, if ROSC = 44.2kΩ, the switching

frequency is set to 500kHz.

Synchronize the switching frequency via an

external clock to improve EMI, efficiency, and

thermal performance.

If setting the switching frequency via the I2C

interface,

float

the

FREQ/SYNC

pin.

The

FSW1:0 bit has the following options:

 00: 200kHz

 01: 400kHz

 10: 1MHz

 11: 2.2MHz

Selecting the Input Capacitor

The input capacitor reduces the surge current

drawn from the input supply, as well as the

switching noise from the device. The input

capacitor impedance at the switching frequency

should be less than the input source impedance.

This prevents the high-frequency switching

current from passing through to the input. Use

ceramic capacitors with X5R or X7R dielectrics

for their low ESR and small temperature

coefficients. For most applications, a 10

μF

ceramic capacitor is sufficient.

Selecting the Inductor

The MPQ3364 requires an inductor to supply a

higher output voltage while being driven by the

input voltage. A larger-value inductor results in

less ripple current, lower peak inductor current,

and less stress on the internal N-channel

MOSFET. However, a larger-value inductor has

a larger physical size, higher series resistance,

and lower saturation current.

Choose an inductor that does not saturate

under the worst-case load conditions. Select

the minimum inductor value to ensure that the

boost converter works in continuous conduction

mode (CCM) with high efficiency and excellent

EMI performance.

Calculate the required inductance value with

Equation (6):





 





2

OUT

SW

LOAD

η V

D (1 D)

L

2

f

I

(6)

Where VOUT is the output voltage, fSW is the

switching frequency, ILOAD is the LED load

current, η is the efficiency, and D can be

estimated with Equation (7):



IN

OUT

V

D1

V

(7)

Where VIN is the input voltage.

For a given inductor value, the inductor DC

current rating should be at least 40% higher

than the maximum input peak inductor current

for

most

applications.

The

inductor

’s DC

resistance should be as small as possible for

higher efficiency.

Selecting the Output Capacitor

The output capacitor keeps the output voltage

ripple small and ensures feedback loop stability.

The output capacitor impedance must be low at

the switching frequency. Ceramic capacitors

with X7R dielectrics are recommended for their

low-ESR characteristics. For most applications,

a 10

μF ceramic capacitor is sufficient.