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EV2108DQ/DK-00A

2A, 6V, 740KHz Synchronous Buck Converter

Monolithic Power Systems 

MP2108 – 2A, 6V, 740KHz SYNCHRONOUS BUCK CONVERTER

Choose the compensation resistor to set the

desired crossover frequency. Determine the

value by the following equation:

R3 = 2π × C2 × fC × VOUT

GEA × GCS VFB

Where GEA is the EA transconductance

(450µA/V) and fC is the desired crossover

frequency (preferably 33KHz).

Choose the compensation capacitor to set the

zero below one fourth of the crossover

frequency. Determine the value by the following

equation:

C3 >

2

π × R3 × fC

Determine if the second compensation

capacitor, C4 is required. It is required if the

ESR zero of the output capacitor happens at

less than half of the switching frequency or:

π × C2 × RESR × fSW > 1

where RESR is the equivalent series resistance

of the output capacitor.

The second compensation capcacitor is

determined by the equation:

C4 = C2 × RESR(max)

R3

Where RESR(MAX) is the maximum ESR of the

output capacitor.

External Boost Diode

It is recommended that an external boost diode

be added to help improve the regulator

efficiency. The diode can be a low cost diode

such as an IN4148 or BAT54.

5V

1

BST

MP2108

3

LX

BOOST

DIODE

10nF

Figure 3—External Boost Diode

This diode is also recommended for high duty

cycle operation (when VOUT >65%).

VIN

MP2108 Rev 1.1

www.MonolithicPower.com

10

10/2/2006

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