MPQ4462 datasheet(12/20 Pages) MPS

12 / 20 page

MPQ4462 – 3.5A, 4MHz, 36V, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED

MPQ4462 Rev. 1.11

www.MonolithicPower.com

7/17/2013

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

APPLICATION INFORMATION

`COMPONENT SELECTION

Frequency

The MPQ4462 has an externally-adjustable

frequency using RFREQ. See Table1 for a list of

recommended RFREQ value for various fS.

Table 1: fS vs. RFREQ

RFREQ (kΩ)

fS (MHz)

3.8

22.1

3.5

3.3

26.7

2.8

33.2

2.5

2.2

45.3

1.8

57.6

1.6

1.4

80.6

1.2

100

133

0.8

200

0.5

340

0.3

536

0.2

Output Voltage

Connecting FB to the tap of a resistor divider

from VOUT to ground sets VOUT such that:

)

(

OUT

Without a load, the MPQ4462 outputs ~20µA

from its high-side BST circuitry. Keep R2 ≤40kΩ

to absorb this small amount of current.

Selecting R2=40.2kΩ, R1 is then:

OUT

R1 50.25 (V

0.8)(k )

=×

−

For example, for VOUT=3.3V and R2=40.2kΩ,

then R1 is 127kΩ.

Inductor

The inductor supplies constant current to the

output load while being driven by the switching

input voltage. A larger inductor will reduce

ripple current and lower output ripple voltage,

but is physically larger, and have a higher

series resistance and/or lower saturation

current.

To choose a balanced inductor value, allow the

peak-to-peak

inductor

ripple

current

approximately equal 30% of the maximum

switching current limit. To ensure that the peak

inductor current is below the maximum switch

current limit estimate and inductor value as:

OUT

ΔIV

⎛⎞

=× −

⎜⎟

⎝⎠

Where VOUT is the output voltage, VIN is the

input voltage, fS is the switching frequency, and

ΔIL is the peak-to-peak inductor-ripple current.

Choose an inductor that will not saturate under

the maximum inductor peak current, which is:

OUT

LOAD

SIN

⎛⎞

× −

⎜⎟

××

⎝⎠

Where ILOAD is the load current.

Output Rectifier Diode

The output rectifier diode supplies the current to

the inductor when the high-side switch is off. To

reduce losses due to the diode forward voltage

and recovery times, use a Schottky diode.

Choose a diode whose maximum reverse

voltage rating exceeds the maximum input

voltage, and whose current rating exceeds the

maximum load current.

Input Capacitor

The input current to the step-down converter is

discontinuous and requires a capacitor to

supply the AC current to the step-down

converter while maintaining the DC input

voltage. Use low-ESR capacitors for the best

performance. Ceramic capacitors are best, but

tantalum or low-ESR electrolytic capacitors may

also suffice.

MPQ4462 Datasheet(PDF) 12 Page - Monolithic Power Systems

MPQ4462 Datasheet(HTML) 12 Page - Monolithic Power Systems

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Datasheet Download

Link URL