EV2109DQ-00A データシートの表示（PDF） - Monolithic Power Systems

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EV2109DQ-00A

Dual 1.2MHz, 800mA Synchronous Step-Down Converter

Monolithic Power Systems 

MP2109 – DUAL 1.2MHz 800mA SYNCHRONOUS STEP-DOWN CONVERTER

OPERATION

IN1/

IN2

EN1/

EN2

FB1/

FB2

BIAS

&

VOLTAGE

REFERENCE

0.6V

FEEDBACK

ERROR\

AMP

ICS

+

SLOPE COMP

EAMP

EAO

--

+

PWM

+PWMCMP

--

+

IAMP

10X

CURRENT --

SENSE

AMP

DH

CC

17pF

1.0MHz OSC

OSCILLATOR

PWM

CONTROL

LOGIC

DL

MAIN

SWITCH

(PCH)

SYNCHRONOUS

RECTIFIER

(NCH)

SW1/

SW2

GND1/

GND2

Figure 1—Functional Block Diagram (Diagram represents ½ of the MP2109)

MP2109_BD02

The MP2109 has dual independent constant

frequency current mode PWM step-down

converters. The MP2109 is optimized for low

voltage, Li-Ion battery powered applications

where high efficiency and small size are critical.

The MP2109 uses external resistor dividers to

set two output voltages independently from

0.6V to 6V. The device integrates both main

switches and synchronous rectifiers, which

provides high efficiency and eliminates the

need for an external Schottky diode. The

MP2109 can achieve 100% duty cycle. The

duty cycle D of each step-down converter is

defined as:

D

=

TON

× fOSC

× 100%

=

VOUT

VIN

× 100%

Where TON is the main switch on time, fOSC is

the oscillator frequency (1.2MHz), VOUT is the

output voltage and VIN is the input voltage.

Current Mode PWM Control

Slope compensated current mode PWM control

provides stable switching and cycle-by-cycle

current limit for superior load and line response

and protection of the internal main switch and

synchronous rectifier. Each channel switches at

a constant frequency (1.2MHz) and regulates

the output voltage. During each cycle the PWM

comparator modulates the power transferred to

the load by changing the inductor peak current

based on the feedback error voltage. During

normal operation, the main switch is turned on

for a certain time to ramp the inductor current at

each rising edge of the internal oscillator, and

switched off when the peak inductor current is

above the error voltage. When the main switch

is off, the synchronous rectifier will be turned on

immediately and stay on until the next cycle

starts.

MP2109 Rev.1.4

www.MonolithicPower.com

5

10/16/2006

MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.

© 2006 MPS. All Rights Reserved.

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