EV2354DS-00A 查看數據表（PDF） - Monolithic Power Systems

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EV2354DS-00A

2A, 23V, 380KHz Step-Down Converter

Monolithic Power Systems 

MP2354 can be optimized for a wide range of

capacitance and ESR values.

Output Rectifier Diode

The output rectifier diode supplies the current to

the inductor when the upper transistor M1 is off.

Use a Schottky diode to reduce losses due to

the diode forward voltage and recovery times.

The DC gain of the voltage feedback loop is

given by:

A VDC

= RLOAD

× GCS

× A VEA

×

VFB

VOUT

Where AVEA is the error amplifier voltage gain,

400V/V; GCS is the current sense

transconductance, 1.95A/V; RLOAD is the load

resistor value.

Choose a diode whose maximum reverse

The system has two poles of importance. One

voltage rating is greater than the maximum

input voltage, and whose current rating is

greater than the maximum load current.

L Table 2 provides the Schottky diode part

A numbers based on the maximum input voltage

I and current rating.

T LY Table 2—Schottky Rectifier Selection Guide

N N E VIN(Max)

2A Load Current

Part Number

Vendor (5)

15V

30BQ015

4

E O T B220

1

20V

SK23

6

D SR22

6

I E U 20BQ030

4

B230

1

F S B 26V

SK23

6

I SR23

3, 6

N U SS23

2, 3

R Note:

O 5) Refer to Table 3 for Rectifier Manufacturers

L T Table 3—Schottky Diode Manufacturers

C A S # Vendor

I 1 Diodes, Inc.

S N 2 Fairchild Semiconductor

D 3 General Semiconductor

P R 4 International Rectifier

5 On Semiconductor

M E T 6 Pan Jit International

Web Site

www.diodes.com

www.fairchildsemi.com

www.gensemi.com

www.irf.com

www.onsemi.com

www.panjit.com.tw

T O Compensation

MP2354 employs current mode control for easy

N N compensation and fast transient response. The

I system stability and transient response are

controlled through the COMP pin. COMP pin is

O the output of the internal transconductance

D error amplifier. A series capacitor-resistor

is due to the compensation capacitor (C3) and

the output resistor of error amplifier, and the

other is due to the output capacitor and the load

resistor. These poles are located at:

fP1

=

GEA

2π × C3 × A VEA

fP2

=

1

2π × C2 × RLOAD

Where GEA is the error

transconductance, 770µA/V.

amplifier

The system has one zero of importance, due to

the compensation capacitor (C3) and the

compensation resistor (R3). This zero is located

at:

fZ1

=

1

2π × C3 × R3

Smaller fZ1 provides more phase margin, but

longer transient settling time. A trade-off has to

be made between the stability and the transient

response. A typical value is less than one-fourth

of the crossover frequency.

The system may have another zero of

importance, if the output capacitor has a large

capacitance and/or a high ESR value. The zero,

due to the ESR and capacitance of the output

capacitor, is located at:

fESR

=

1

2π × C2 × RESR

combination sets a pole-zero combination to

control the characteristics of the control system.

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