MPQ2166B

– 6V, DUAL 2A/2A OR 3A/1A SYNC BUCK REGULATOR, AEC-Q100

MPQ2166B Rev. 1.0

MonolithicPower.com

21

1/18/2022

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

© 2022 MPS. All Rights Reserved.

APPLICATION INFORMATION

Setting the Output Voltage

The external resistor divider sets VOUT. The

feedback resistor (R1) also sets the feedback

(FB)

loop

bandwidth

with

the

internal

compensation. Figure 5 shows the feedback

network.

FB

VOUT

R1

R2

C1

Figure 5: Feedback Network

If R1 is estimated to be 10

0kΩ, R2 can then be

calculated using Equation (2):

OUT

R1

R2

V

1

0.6V

=

−

(2)

Table 2 lists the recommended feedback resistor

values for common output voltages.

Table 2: Resistor Selection vs. Output Voltage

Setting

VOUT (V)

R1

(kΩ)

R2

(kΩ)

C1 (pF)

1.2

100

100

22

1.5

100

66.5

22

1.8

100

49.9

22

2.5

100

31.6

22

3.3

100

22.1

22

Selecting the Inductor

It is recommended to use an inductor with a DC

current rating at least 25% greater than the

maximum load current for most applications. For

the best efficiency, the inductor DC resistance

should be below

20mΩ. For most designs, the

inductance can be estimated with Equation (3):

SW

L

IN

OUT

IN

OUT

f

I

V

)

V

-

(V

V

L









=

(3)

Where

ΔIL is inductor ripple current.

Choose

ΔIL to be approximately 30% of the

maximum load current. The maximum inductor

peak current (IL(MAX)) can be calculated using

Equation (4):

L

L(MAX)

LOAD

I

II

2



=+

(4)

Selecting the Input Capacitor

The input capacitor reduces the surge current

drawn from the input and the switching noise

from the device. The input capacitor impedance

at fSW should be below the input source

impedance to prevent high-frequency switching

current from passing to the input source.

Ceramic capacitors with X5R or X7R dielectrics

are highly recommended because of their low

ESR and small temperature coefficients. For

most applications, a 22µF capacitor is sufficient.

Selecting the Output Capacitor

The output capacitor (CO) keeps the output

voltage ripple small and ensures a stable

regulation loop. The CO impedance should be

low at fSW. It is recommended to use ceramic

capacitors with X5R or X7R dielectrics. If an

electrolytic capacitor is used, pay close attention

to the output ripple voltage, extra heating, and

the selection of the upper feedback resistor due

to the large ESR of electrolytic capacitors (see

the Setting the Output Voltage section above).

The output ripple (

∆VOUT) can be estimated using

Equation (5):

(

)

OUT

IN

OUT

OUT

IN

SW

SW

O

V

V

V

1

V

(ESR

)

V

L f

8 f

C

−



=



+

 





(5)

Power Dissipation

IC power dissipation is important in circuit

design, not only because of efficiency concerns,

but also because of the chip’s thermal

requirements. Several parameters influence

power dissipation, such as conduction loss

(PCOND), dead time (DT), switching loss (PSW),

MOSFET driver current (PDR), and supply current

(PS).

Based on these parameters, the power loss

(PLOSS) can be calculated using Equation (6):

LOSS

COND

DT

SW

DR

S

P

P

P

P

P

P

=

+

+

+

+

(6)