MP2269 - 30V, 1A, LOW IQ, SYNCHRONOUS STEP-DOWN CONVERTER

MP2269 Rev. 1.0

www.MonolithicPower.com

11

10/11/2016

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OPERATION

The MP2269 is a synchronous, step-down,

switching regulator with integrated, internal,

high-side and low-side power MOSFETs. It

provides 1A of highly efficient output current

with

current-mode

control.

The

MP2269

features

a

wide

input

voltage

range,

programmable 350kHz to 2.5MHz switching

frequency, external soft start, and current limit.

Its very low operational quiescent current

makes

it

suitable

for

battery-powered

applications.

PWM Control

At

moderate-to-high

output

currents,

the

MP2269 operates in a fixed-frequency, peak-

current-control mode to regulate the output

voltage. A PWM cycle is initiated by the internal

clock. At the rising edge of the clock, the high-

side power MOSFET (HS-FET) is turned on

and remains on until its current reaches the

the high-side power switch is off, the low-side

MOSFET (LS-FET) is turned on and remains on

until the next cycle begins. If the current in the

HS-FET does not reach the COMP-set current

value in one PWM period, the HS-FET remains

on, saving a turn-off operation.

Advanced Asynchronous Mode (AAM)

The MP2269 employs advanced asynchronous

mode (AAM) functionality to optimize efficiency

during light-load or no-load conditions. AAM

mode is selectable. Enable AAM by connecting

MODE to a low level or floating MODE; disable

AAM by connecting MODE to a high level.

If AAM is enabled, the MP2269 first enters non-

synchronous operation for as long as the

inductor current approaches zero at light load. If

the load is further decreased or is at no load,

AAM or sleep mode, which consumes very low

quiescent

current

and

improves

light-load

efficiency further.

In AAM, the internal clock is reset whenever

time is taken as the benchmark for the next

clock. When the load increases, and the DC

operation mode is DCM or CCM, which have a

constant switching frequency.

AAM

(MODE = Low)

Inductor

Current

t

t

t

Load

Decreased

PWM Mode

(MODE = High)

Inductor

Current

t

t

t

Load

Decreased

Figure 2: AAM and PWM Mode

The MP2269 has a mode selection function

(see Figure 2). Pull MODE low or float MODE to

set auto PFM/PWM mode. Pull MODE high to

set forced PWM mode. MODE is pulled down

internally. Select MODE before the part starts

up.

Error Amplifier (EA)

The error amplifier (EA) compares the FB

voltage with the internal reference (typically

0.8V) and outputs a current proportional to the

difference between the two. This output current

is used to charge the internal compensation

the power MOSFET current.

BIAS and VCC Regulator

Most of the internal circuitry is powered by the

internal regulator. The MP2269 has two internal

regulators (see Figure 3). The regulator LDO1

takes the VIN input and operates in the full VIN

range. When VIN is greater than 5V, the output

of the regulator is in full regulation, and VCC is

5V. When VIN is lower than 5V, the output

degrades.

Another regulator, LDO2, is powered by BIAS.

Connect BIAS to an external power source, and

keep the BIAS voltage higher than 4.8V. VCC

and the internal circuit are then powered by

of the regulator is in full regulation, and VCC is

Once LDO2 is enabled, LDO1 is disabled. For a

5V output application, BIAS is recommended to

The diode (D1) between BIAS and the internal

circuit is used for reverse blocking. Since LDO1

less than VIN. Connect BIAS to GND if BIAS is

not used.