MPQ4462DN datasheet(14/20 Pages) MPS

14 / 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.

compensation resistor (R3). This pole is

located at:

2C6 R3

π×

The compensator shapes the converter transfer

function for a desired loop gain. The feedback

loop’s

unity-gain

crossover

frequency

important. Lower crossover frequencies result

slow line and load transient responses, while

higher crossover frequencies increase system

instability. For most applications, set the

crossover frequency to ~0.1×fS. Table 2 lists

some typical compensation-component values

for standard output voltages. The component

values

are

optimized

for

fast

transient

responses and good stability at given conditions.

Table 2: Compensation Values for Typical

Output Voltage/Capacitor Combinations

VOUT

(V)

L (µH)

(µF)

(kΩ)

(pF)

1.8

4.7

105

100

None

2.5

4.7 - 6.8

54.9

220

None

3.3

6.8 -10

68.1

220

None

15 - 22

100

150

None

22 - 33

147

150

None

To optimize the compensation components for

conditions not listed in Table 2:

1. Choose R3 for the desired crossover

frequency:

COUT

2C2 f

π×

=×

Where fC is the desired crossover frequency.

2. Choose C3 for the desired phase margin. For

applications with typical inductor values, setting

the compensation zero (fZ1) below 0.25×fC

provides sufficient phase margin. C3 must meet

the following criterion:

3. Determine if C6 is required. Add C6 if the

ESR zero of the output capacitor is located at

<0.5×fC, or if the following relationship is true:

ESR

2C2 R

π×

Select C6 to set the pole (fP3) at the the ESR

zero. Determine the C6 as:

ESR

C2 R

High-Frequency Operation

Set the MP4462’s switching frequency up to

4MHz through an external resistor. For

switching frequencies above 2MHz, take the

following into consideration:

• The minimum ON-time is ~80ns. Pulse

skipping occurs more often at higher

switching frequencies due to the minimum

ON-time.

• The recommended operating voltage is

<12V, and <24V at 2MHz. Refer to Figure 2

for more information.

Recommended VIN (max)

vs Switching Frequency

1500 2000 2500 3000 3500 4000

VOUT=3.3V

fs (KHz)

VOUT=2.5V

Figure 2: Recommended Max. VIN vs fS

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