A7131MP8R [AITSEMI]

DC-DC CONVERTER/ BUCK (STEP-DOWN) SYNCHRONOUS BUCK CONVERTER;


型号：	A7131MP8R
厂家：	AiT Semiconductor
描述：	DC-DC CONVERTER/ BUCK (STEP-DOWN) SYNCHRONOUS BUCK CONVERTER DC-DC转换器
文件：	总12页 (文件大小：436K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

AiT Semiconductor Inc.

A7131

DC-DC CONVERTER/ BUCK (STEP-DOWN)

www.ait-ic.com

3.0A 1.5MHz SYNCHRONOUS BUCK CONVERTER

DESCRIPTION

FEATURES

The A7131 is a high-efficiency, DC-to-DC step-down

switching regulators, capable of delivering up to 3.0A

of output current. The A7131 operates from an input

voltage range of 2.5V to 5.5V and provides an output

voltage from 0.6V to V_IN-0.3V, making the device

A7131 ideal for low voltage power conversions.

Running at a fixed frequency of 1.5MHz allows the

use of small external components, such as ceramic

input and output caps, as well as small inductors,

while still providing low output ripples. This low noise

output along with its excellent efficiency achieved by

the internal synchronous rectifier, making A7131 an

ideal green replacement for large power consuming

linear regulators.



High Efficiency: Up to 95%

Capable of Delivering 3.0A

1.5MHz Switching Frequency

No External Schottky Diode Needed

Low dropout 100% Duty operation

Internal Compensation and Soft-Start

Current Mode control

0.6V Reference for Low Output voltages

Logic Control Shutdown (I_Q<1uA)

Over Voltage Protection

Short Circuit Protection

Thermal shutdown and UVLO

Available in PSOP8 Package

APPLICATION

Internal soft-start control circuitry reduces inrush

current. Short-circuit and thermal-overload protection

improves design reliability.



Digital Cameras

Set top boxes

Wireless and DSL Modems

USB supplied Devices in Notebooks

Portable Devices

The A7131 is available in PSOP8 package.

ORDERING INFORMATION

TYPICAL APPLICATION

Package Type

Part Number

A7131MP8R

A7131MP8VR

PSOP8

MP8

SPQ: 3,000pcs/Reel

V: Halogen free Package

R: Tape & Reel

Note

AiT provides all RoHS products

REV2.0

- APR 2012 RELEASED, NOV 2018 UPDATED -

- 1 -

AiT Semiconductor Inc.

A7131

DC-DC CONVERTER/ BUCK (STEP-DOWN)

www.ait-ic.com

3.0A 1.5MHz SYNCHRONOUS BUCK CONVERTER

PIN DESCRIPTION

Top View

Pin #

Symbol

Function

Not Connected

Power Supply Input Pin. Must be closely decoupled to GND with at least 10uF

ceramic cap.

Inductor connection. Connect an inductor between SW and the regulator output.

GND

Ground

Feedback input. Connect an external resistor divider from the output to FB and

GND to set the output to a voltage between 0.6V and Vin

Not Connected

Enable pin for the IC. Drive the pin to high to enable the part, and low to disable

No Connection.

REV2.0

- APR 2012 RELEASED, NOV 2018 UPDATED -

- 2 -

AiT Semiconductor Inc.

A7131

DC-DC CONVERTER/ BUCK (STEP-DOWN)

www.ait-ic.com

3.0A 1.5MHz SYNCHRONOUS BUCK CONVERTER

ABSOLUTE MAXIMUM RATINGS

Max Input Voltage

6.0V

150°C

T_J, Max Operating Junction Temperature

T_A, Ambient Temperature

-40°C ~ +85°C

Maximum Power Dissipation

T_S, Storage Temperature

Lead Temperature & Time

PSOP8

-40°C ~ +150°C

260°C, 10s

Stress beyond above listed ꢀAbsolute Maximum Ratingsꢁ may lead permanent damage to the device. These are stress ratings only and

operations of the device at these or any other conditions beyond those indicated in the operational sections of the specifications are not

implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

RECOMMENDED OPERATING CONDITIONS

Parameter

Symbol

V_IN

Value

Units

V_INSupply Voltage

Operating Temperature

2.5 ~ 5.5

-40 ~ +85

T_OPT

°C

REV2.0

- APR 2012 RELEASED, NOV 2018 UPDATED -

- 3 -

AiT Semiconductor Inc.

A7131

DC-DC CONVERTER/ BUCK (STEP-DOWN)

www.ait-ic.com

3.0A 1.5MHz SYNCHRONOUS BUCK CONVERTER

ELECTRICAL CHARACTERISTICS

V_IN=5.0V, L=2.2uH, T_A=25°C, unless otherwise specified.

Parameter

Input Voltage Range

Feedback Voltage

Feedback Leakage Current

Quiescent Current

Shutdown Current

Switching Frequency

PMOSFET R_DSON

Symbol

Conditions

Min.

Typ.

Max.

Unit

V_IN

2.5

5.5

V_FB

0.588

0.6

0.1

0.612

I_FB

0.4

MHz

mΩ

I_Q

Active, V_FB=0.65V

Shutdown

I_SD

f_SW

1.5

100

R_ONP

R_ONN

V_UVLO

V_1HYS

I_LIMIT

NMOSFET R_DSON

UVLO Threshold

2.5

UVLO Hysteresis

0.15

Peak Current Limit

5.0

V_IN=5.5V, V_SW=0 or5.5V,

V_EN=0V

SW Leakage Current

I_SW

Over Voltage Threshold

OVP Hysteresis

V_OVP

V_2HYS

I_EN

6.15

0.3

EN Leakage Current

Soft Start Time

t_SOFT

V_ENH

V_ENL

T_SD

350

EN Input High Voltage

EN Input Low Voltage

Thermal Shutdown

1.5

0.4

150

℃

Hysteresis Thermal Shutdown

Discharge Resistor

T_HSD

R_dis

REV2.0

- APR 2012 RELEASED, NOV 2018 UPDATED -

- 4 -

AiT Semiconductor Inc.

A7131

DC-DC CONVERTER/ BUCK (STEP-DOWN)

www.ait-ic.com

3.0A 1.5MHz SYNCHRONOUS BUCK CONVERTER

TYPICAL PERFORMANCE CHARACTERISTICS

C_IN=22μF, C_OUT=22μF, L=2.2μH, Ce=22pF, Tested under T_A=25°C, unless otherwise specified

Efficiency vs. Load Current

Output Voltage vs. Output Current

Operation Temperature vs. Output Voltage

Input Voltage vs. Output Voltage

REV2.0

- APR 2012 RELEASED, NOV 2018 UPDATED -

- 5 -

AiT Semiconductor Inc.

A7131

DC-DC CONVERTER/ BUCK (STEP-DOWN)

www.ait-ic.com

3.0A 1.5MHz SYNCHRONOUS BUCK CONVERTER

Start Up Waveform

Shutdown Waveform

REV2.0

- APR 2012 RELEASED, NOV 2018 UPDATED -

- 6 -

AiT Semiconductor Inc.

A7131

DC-DC CONVERTER/ BUCK (STEP-DOWN)

www.ait-ic.com

3.0A 1.5MHz SYNCHRONOUS BUCK CONVERTER

DETAILED INFORMATION

Operation Description

The A7131 high-efficiency switching regulator is a small, simple, DC-to-DC step-down converter capable of

delivering up to 3.0A of output current. The device operates in pulse-width modulation (PWM) at 1.5MHz from

a 2.5V to 5.5V input voltage and provides an output voltage from 0.6V to V_IN-0.3V, making the A7131 ideal for

on-board post-regulation applications. An internal synchronous rectifier improves efficiency and eliminates the

typical Schottky free-wheeling diode. Using the on resistance of the internal high-side MOSFET to sense

switching currents eliminates current-sense resistors, further improving efficiency and cost.

Loop Operation

A7131 uses a PWM current-mode control scheme. An open-loop comparator compares the integrated

voltage-feedback signal against the sum of the amplified current-sense signal and the slope compensation

ramp. At each rising edge of the internal clock, the internal high-side MOSFET turns on until the PWM

comparator terminates the on cycle. During this on-time, current ramps up through the inductor, sourcing

current to the output and storing energy in the inductor. The current mode feedback system regulates the

peak inductor current as a function of the output voltage error signal. During the off cycle, the internal

high-side P-channel MOSFET turns off, and the internal low-side N-channel MOSFET turns on. The inductor

releases the stored energy as its current ramps down while still providing current to the output.

Current Sense

An internal current-sense amplifier senses the current through the high-side MOSFET during on time and

produces a proportional current signal, which is used to sum with the slope compensation signal. The

summed signal then is compared with the error amplifier output by the PWM comparator to terminate the on

cycle.

Output OVP

If the output voltage exceeds 120% of the regulation level for more than 20us, the A7131 will turn off both

power switches and turn on the discharge switch, entering over-voltage protection. I will remain in this state

until IN and EN voltage is recycled.

Short Protection

After the soft start is over, if the output voltage falls below 40% of the regulation level, the A7131 will turn off

both power switches, entering the short circuit protection. It will remain in this state until IN or EN voltage is

recycled.

REV2.0

- APR 2012 RELEASED, NOV 2018 UPDATED -

- 7 -

AiT Semiconductor Inc.

A7131

DC-DC CONVERTER/ BUCK (STEP-DOWN)

www.ait-ic.com

3.0A 1.5MHz SYNCHRONOUS BUCK CONVERTER

Current Limit

There is a cycle-by-cycle current limit on the high-side MOSFET of 5.0A (min). When the current flowing out of

SW exceeds this limit, the high-side MOSFET turns off and the synchronous rectifier turns on. A7131 utilizes

a frequency fold-back mode to prevent overheating during short-circuit output conditions. The device enters

frequency fold-back mode when the FB voltage drops below 200mV, limiting the current to 5.0A and reducing

power dissipation. Normal operation resumes upon removal of the short-circuit condition.

Soft-start

A7131 has a internal soft-start circuitry to reduce supply inrush current during startup conditions. When the

device exits under-voltage lockout (UVLO), shutdown mode, or restarts following a thermal-overload event,

the soft-start circuitry slowly ramps up current available at SW.

UVLO and Thermal Shutdown

If IN drops below 2.5V, the UVLO circuit inhibits switching. Once IN rises above 2.5V, the UVLO clears, and

the soft-start sequence activates. Thermal-overload protection limits total power dissipation in the device.

When the junction temperature exceeds T_J= +150°C, a thermal sensor forces the device into shutdown,

allowing the die to cool. The thermal sensor turns the device on again after the junction temperature cools by

15°C, resulting in a pulsed output during continuous overload conditions. Following a thermal-shutdown

condition, the soft-start sequence begins.

REV2.0

- APR 2012 RELEASED, NOV 2018 UPDATED -

- 8 -

AiT Semiconductor Inc.

A7131

DC-DC CONVERTER/ BUCK (STEP-DOWN)

www.ait-ic.com

3.0A 1.5MHz SYNCHRONOUS BUCK CONVERTER

APPLICATION INFORMATION

Setting Output Voltages

Output voltages are set by external resistors. The FB threshold is 0.6V.

R₁= R₂[(V_OUT/ 0.6) - 1]

Set R₂to 100k, then R₁can be easily derived from the above equation.

Output Capacitor C_OUT

The output capacitor is selected to handle the output ripple noise requirements, both steady state ripple and

transient requirements must be taken into consideration when selecting this capacitor. For the best

performance, it is recommended to use X5R or better grade ceramic capacitor with 6.3V rating and greater

than 22uF capacitance.

Input Capacitor Selection

This ripple current through input capacitor is calculated as:

I_{CIN_RMS}= I_OUT

D(1-D)

This formula has a maximum at V_IN=2V_OUTcondition, where I_{CIN_RMS}=I_OUT/2. This simple worst-case condition

is commonly used for the DC-DC design.

With the maximum load current at 2.5A, A typical X5R or better grade ceramic capacitor with 6.3V rating and

more than 1pcs 22uF capacitor can handle this ripple current well. To minimize the potential noise problem,

ceramics ceramic capacitor should really be placed close to IN and GND pins. Care should be taken to

minimize the loop area formed by C_INand IN/GND pins.

Inductor Selection

There are several considerations in choosing this induction.

1. Choose the inductance to provide the desired ripple current. It is suggested to choose the ripple to be

about 40% of maximum output current. The inductance is calculated as:

REV2.0

- APR 2012 RELEASED, NOV 2018 UPDATED -

- 9 -

AiT Semiconductor Inc.

A7131

DC-DC CONVERTER/ BUCK (STEP-DOWN)

www.ait-ic.com

3.0A 1.5MHz SYNCHRONOUS BUCK CONVERTER

OUT (1- VOUT/

SW xIOUT, MAX x 40%

IN,MAX

)

L 

Where f_SWis the switching frequency and I_OUT.MAXis the maximum load current.

The A7131 regulator IC is quite tolerant of different ripple current amplitude. Consequently, the final

choice of inductance can be slightly off the calculation value without significantly impacting the

performance.

2. The saturation current rating of the inductor must be selected to be greater than the peak inductor current

under full load conditions.

OUT(1- VOUT/VIN,MAX)

I_SAT,MIN> I_OUT,MAX

2 x fSW x L

3. The DCR of inductor and the ore loss at the switching frequency must be low enough to achieve the

desired efficiency requirement. It is desirable to choose an inductor with DCR<50mΩ to achieve a good

overall efficiency.

Layout Consideration

Layout is critical to achieve clean and stable operation. The switching power stage requires particular

attention. Follow these guidelines for good PC board layout:

Place decoupling capacitors as close to the IC as possible

Connect input and output capacitors to the same power ground node with a star ground configuration

then to IC ground.

Keep the high-current paths as short and wide as possible. Keep the path of switching current (C_INto IN

and C_INto GND) short. Avoid vias in the switching paths.

If possible, connect IN, SW, and GND separately to a large copper area to help cool the IC to further

improve efficiency and long-term reliability.

Ensure all feedback connections are short and direct. Place the feedback resistors as close to the IC as

possible.

Route high-speed switching nodes away from sensitive analog area.

REV2.0

- APR 2012 RELEASED, NOV 2018 UPDATED -

- 10 -

AiT Semiconductor Inc.

A7131

DC-DC CONVERTER/ BUCK (STEP-DOWN)

www.ait-ic.com

3.0A 1.5MHz SYNCHRONOUS BUCK CONVERTER

PACKAGE INFORMATION

Dimension in PSOP8 (Unit: mm)

REV2.0

- APR 2012 RELEASED, NOV 2018 UPDATED -

- 11 -

AiT Semiconductor Inc.

A7131

DC-DC CONVERTER/ BUCK (STEP-DOWN)

www.ait-ic.com

3.0A 1.5MHz SYNCHRONOUS BUCK CONVERTER

IMPORTANT NOTICE

AiT Semiconductor Inc. (AiT) reserves the right to make changes to any its product, specifications, to

discontinue any integrated circuit product or service without notice, and advises its customers to obtain the

latest version of relevant information to verify, before placing orders, that the information being relied on is

current.

AiT Semiconductor Inc.'s integrated circuit products are not designed, intended, authorized, or warranted to

be suitable for use in life support applications, devices or systems or other critical applications. Use of AiT

products in such applications is understood to be fully at the risk of the customer. As used herein may involve

potential risks of death, personal injury, or server property, or environmental damage. In order to minimize

risks associated with the customer's applications, the customer should provide adequate design and

operating safeguards.

AiT Semiconductor Inc. assumes to no liability to customer product design or application support. AiT

warrants the performance of its products of the specifications applicable at the time of sale.

REV2.0

- APR 2012 RELEASED, NOV 2018 UPDATED -

- 12 -

A7131MP8R [AITSEMI]

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