MP1583 查看數據表（PDF） - Monolithic Power Systems

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MP1583

3A, 23V Step Down Converter

Monolithic Power Systems 

Monolithic Power Systems

MP1583

3A, 23V

Step Down Converter

Figure 2: Functional Block

IN 2

Internal

Regulators

EN 7

Oscillator

42/380KHz

Shutdown

Comparator

0.7V

1uA

Σ

Slope

Compensation

CLK

2.285/2.495V

Lockout

Comparator

Current

Sense

Amplifier

Current

Comparator

5V

SQ

RQ

100K

1.8V

1 BS

M1

3 SW

M2

4 GND

Frequency

Foldback

Comparator

0.7V

5 FB

1.22V

Error Amplifier

gm= 800uA/Volt

6 COMP

8 SS

Functional.Description

The MP1583 is a current-mode step-down

regulator. It regulates input voltages from

4.75V to 23V down to an output voltage as low

as 1.22V, and is able to supply up to 3A of

load current.

The MP1583 uses current-mode control to

regulate the output voltage. The output

voltage is measured at FB through a resistive

voltage divider and amplified through the

internal error amplifier. The output current of

the transconductance error amplifier is

presented at COMP where a network

compensates the regulation control system.

The voltage at COMP is compared to the

switch current measured internally to control

the output voltage.

The converter uses an internal n-channel

MOSFET switch to step-down the input voltage

to the regulated output voltage. Since the

MOSFET requires a gate voltage greater than

the input voltage, a boost capacitor connected

between SW and BS drives the gate. The

capacitor is internally charged while SW is low.

An internal 10Ω switch from SW to GND is

used to insure that SW is pulled to GND when

SW is low to fully charge the BS.capacitor.

Application Information

Setting the Output Voltage

The output voltage is set using a resistive

voltage divider from the output voltage to FB

(see Figure 3). The voltage divider divides the

output voltage down by the ratio:

VFB = VOUT * R2 / (R1 + R2)

Thus the output voltage is:

VOUT = 1.222 * (R1 + R2) / R2

R2 can be as high as 100KΩ, but a typical

value is 10KΩ. Using that value, R1 is

determined by:

R1 ~= 8.18 * (VOUT – 1.222) (KΩ)

For example, for a 3.3V output voltage, R2 is

10KΩ, and R1 is 17KΩ.

MP1583 Rev 2.0_06/30/04

www.monolithicpower.com

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