MP2313 – 24V, 1A SYNC STEP DOWN CONVERTER

MP2313 Rev. 1.0

www.MonolithicPower.com

11

9/1/2014

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OPERATION

The MP2313 is a high frequency synchronous

rectified step-down switch mode converter with

built in internal power MOSFETs. It offers a

very compact solution to achieve 1A continuous

output current over a wide input supply range

with excellent load and line regulation.

The MP2313 operates in a fixed frequency,

peak current control mode to regulate the

output voltage. A PWM cycle is initiated by the

internal clock. The integrated high-side power

MOSFET is turned on and remains on until its

current reaches the value set by the COMP

voltage. When the power switch is off, it

remains off until the next clock cycle starts. If, in

83% of one PWM period, the current in the

power MOSFET does not reach the COMP set

current value, the power MOSFET will be

forced to turn off.

Internal Regulator

Most of the internal circuitries are powered from

the 5V internal regulator. This regulator takes

the VIN input and operates in the full VIN range.

When VIN is greater than 5.0V, the output of

the regulator is in full regulation. When VIN is

lower than 5.0V, the output decreases, a 0.1uF

ceramic capacitor for decoupling purpose is

required.

Error Amplifier

The error amplifier compares the FB pin voltage

with the internal 0.8V reference (REF) and

outputs a COMP voltage, which is used to

control the power MOSFET current. The

optimized

internal

compensation

network

minimizes the external component counts and

simplifies the control loop design.

AAM Operation

The

MP2313

has

AAM

(Advanced

Asynchronous Modulation) power-save mode

for light load. Connect a resistor from AAM pin

to GND to set AAM voltage. Under the heavy

When the clock goes high, the high-side power

reaches the value set by the COMP voltage.

Under the light load condition, the value of

clock is blocked, thus the MP2313 skips some

pulses for PFM (Pulse Frequency Modulation)

mode and achieves the light load power save.

Figure 2: Simplified AAM Control Logic

Enable control

EN is a digital control pin that turns the

regulator on and off. Drive EN high to turn on

the regulator, drive it low to turn it off. There is

an internal 1MEG resistor from EN to GND thus

EN can be floated to shut down the chip. Also

EN pin voltage was clamped to around 6.5V by

an internal zener-diode. Please use large

enough pull up resistor connecting between VIN

and EN to limit the EN input current which

should be less than 100uA. Generally, around

100k resistor should be large enough for all the

applications.

For example, with 12V connected to Vin,

Connecting the EN pin is directly to a voltage

source without any pullup resistor requires

limiting the amplitude of the voltage source to

≤

6V to prevent damage to the Zener diode.