AP3445_技术文档

AP3445/L

1MHZ, 2A STEP-DOWN DC-DC BUCK CONVERTER

Description

Pin Assignments

The AP3445 and AP3445L is a 2A step-down DC-DC converter. At

heavy load, the constant-frequency PWM control performs excellent

stability and transient response. No external compensation

components are required.

(Top View)

Pin 1 Mark

The AP3445/L supports a range of input voltages from 2.7V to 5.5V

allowing the use of a single Li+/Li-polymer cell, multiple Alkaline/NiMH

cell, and other standard power sources. The output voltage is

adjustable from 0.6V to the input voltage. The AP3445/L employs

internal power switch and synchronous rectifier to minimize external

part count and realize high efficiency. During shutdown, the input is

disconnected from the output and the shutdown current is less than

1μA. Other key features include over-temperature and short circuit

protection, and under-voltage lockout to prevent deep battery

discharge.

6

5

4

FB

1

2

3

EN

PG

GND

LX

VIN

The AP3445/L delivers 2A maximum output current while consuming

only 55μA of no-load quiescent current. Ultra-low R_DS(ON)integrated

MOSFETs and 100% duty cycle operation make the AP3445/L an

ideal choice for high output voltage, high current applications which

require a low dropout threshold. Pulse skip mode to maintain high

efficiency at light-load conditions.

SOT26 (SC74R)

The AP3445/L is available in SOT26 (SC74R) package.

Features

Applications



Input Voltage: 2.7V to 5.5V



Post DC-DC Voltage Regulation

Output Voltage: 0.6V to V_IN

Set Top Boxes

Notebook Computer

PAD

0.6V Reference Voltage with ±1.5% Precision

55µA (Typ) No Load Quiescent Current

Shutdown Current: <1µA

100% Duty Cycle Operation

1MHz Switching Frequency

No External Compensation Required

Short Circuit Protection

445L: Latch Off Protection

AP3445: Hiccup Mode Protection

Over Voltage Protection



3445L: Latch Off Protection

445: Non Latch Off Protection

Thermal Shutdown



SOT26 (SC74R) Package

Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)

Halogen and Antimony Free. “Green” Device (Note 3)

Notes:

1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS), 2011/65/EU (RoHS 2) & 2015/863/EU (RoHS 3) compliant.

2. See https://www.diodes.com/quality/lead-free/ for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green"

and Lead-free.

3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and

<1000ppm antimony compounds.

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March 2018

AP3445/L

Document number: DS39755 Rev. 1 - 2

AP3445/L

Typical Applications Circuit

V_IN=2.7V to 5.5V

VIN

C_IN

22mF

L1 2.2mH

V_OUT=1.8V

LX

FB

OFF ON

R1

EN

PG

C1

22pF

C_OUT

200kΩ

22mFx2

GND

R2

100kΩ

Pin Descriptions

Pin Number

Pin Name

Function

Enable control input. Force this pin voltage above 1.5V enables the chip, and below

0.4V shuts down the device.

1

EN

2

3

4

GND

LX

Ground pin

The drains of the internal main and synchronous power MOSFET.

Bias supply. Chip main power supply pin

VIN

Power good indicator, open drain output. PG is pulled up to VIN when the output

voltage is within 20% of the regulation level, otherwise it is low

5

6

PG

FB

Feedback voltage to internal error amplifier, the threshold voltage is 0.6V.

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March 2018

AP3445/L

Document number: DS39755 Rev. 1 - 2

AP3445/L

Functional Block Diagram

4

VIN

1.5M OSC

+

SLOPE COMP

PWM

COMP

+

_

6

FB

IAMP

_

____

OSC

FREQ

SHIFT

Q

S

R

SWITCHING

_

3

LOGIC AND

BLOCKING

CIRCUIT

_

Q

LX

ANTI -

SHOOT

THRU

0.6V REF

+

EA

1

5

EN

PG

CONTROL

LOGIC

2

SHUTDOWN

GND

Functional Block Diagram of AP3445/L

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March 2018

AP3445/L

Document number: DS39755 Rev. 1 - 2

AP3445/L

Absolute Maximum Ratings (Note 4)

Symbol

V_IN

Parameter

Rating

-0.3 to 6

Unit

V

Input Voltage

V_EN

V_FB

V_LX

EN Pin Voltage

-0.3 to V_IN+0.3

-3 to V_IN+3 for <20ns

-0.3 to V_IN+0.3

0.588

V

FB Pin Voltage

V

LX Pin Voltage

V

V_LX

LX Pin Voltage

V

V_FB

P_D

Feedback Pin Voltage

Power Dissipation (On PCB, T_A= +25°C)

V

W

θ_JA

Thermal Resistance (Junction to Ambient)

170

°C/W

θ_JC



Thermal Resistance (Junction to Case, Simulation)

Operating Junction Temperature

130

+150

°C /W

°C

V

T_J

T_STG

V_HBM

V_CDM

Storage Temperature

-55 to +150

2000

ESD (Human Body Model, JESD22-A114)

ESD (Charge Device Mode, JESD22-C101)

1000

V

Note:

4. Stresses greater than those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and

functional operation of the device at these or any other conditions beyond those indicated under “Recommended Operating Conditions” is not implied.

Exposure to “Absolute Maximum Ratings” for extended periods may affect device reliability.

Recommended Operating Conditions

Symbol

V_IN

Parameter

Min

2.7

-40

Max

5.5

Unit

V

Supply Voltage

T_J

Junction Temperature Range

Operating Ambient Temperature

+125

+85

°C

T_A

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March 2018

AP3445/L

Document number: DS39755 Rev. 1 - 2

AP3445/L

Electrical Characteristics (@T_A= +25ºC , V_IN= 5.0V, V_OUT= 2.5V, C_OUT= 22µF*2, L = 2.2µH, unless otherwise specified.)

Symbol

Parameters

Conditions

Min

Typ

Max

Unit

VIN

V_IN

V_OUT

I_Q

Input Voltage Range

Output Voltage Range

Quiescent Current

–

2.7

0.6

–

5.5

V_IN

–

V

–

V_FB= 0.65V

V_EN= 0V

V_INRises

V_INFalls

55

0.1

2.4

0.2

µA

V

I_SD

Shutdown Current

–

1

V_UVLO

V_HYS

Input UVLO Threshold

Input UVLO Hysteresis

–

2.5

–

V

Feedback Input

V_FB

Regulated Feedback Voltage

FB Leakage Current

–

0.591

–

0.6

–

0.609

0.2

–

V

µA

A

I_FB

V_FB= 1V

I_LIM

Peak Inductor Current

–

2.5

–

Oscillator

f_OSC

Oscillator Frequency

Maximum Duty Cycle

–

0.8

1

1.2

MHz

%

D_MAX

100

–

MOSFET

I_LX= 100mA High Side

I_LX= 100mA Low Side

–

100

60

–

mΩ

Drain-Source On-State

Resistance

R_DS(ON)

Output Discharge Switch On

Resister

R_DISCH

–

50

–

Ω

EN Pin

V_ENH

EN Threshold High

EN Threshold Low

EN Leakage Current

–

1.5

–

V

V_ENL

–

0.4

1.0

I_EN

V_IN= V_EN=5V

-1.0

µA

Protection

Short Circuit Protection Latch

Off Threshold

V_SCP

AP3445L only

–

0.42

30

–

V

Short Circuit Protection Delay

Time

T_{DELAY_SCP}

–

ms

T_OTP

T_DTH

Over Temperature Protection

OTP Hysteresis

–

+150

+20

0.72

6.3

–

°C

V

–

V_OVP

V_OUTOver Voltage Protection

V_INOver Voltage Protection

IOVP Hysteresis

AP3445L only

V_INRises

V_INFalls

V_IOVP

V

V_IHSY

0.35

V

Soft Start

t_SS

Soft-start Time

–

0.7

1.0

1.3

ms

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March 2018

AP3445/L

Document number: DS39755 Rev. 1 - 2

AP3445/L

Performance Characteristics (@T_A= +25°C, V_IN= 5V, V_OUT= 1.8V, unless otherwise specified.)

Efficiency vs. Load Current

Output Voltage vs. Output Current

1.817

1.816

1.815

1.814

1.813

1.812

1.811

1.810

1.809

1.808

1.807

100

95

90

85

80

75

70

65

60

V_IN=5V, V_OUT=1.0V

V_IN=5V, V_OUT=1.8V

V_IN=5V, V_OUT=3.3V

V_IN=5.0V Vo=1.8V

0

200

400

600

800 1000 1200 1400 1600 1800 2000

Ouput Current (mA)

10

100

1000

Output Current (mA)

Output Voltage vs. Input Voltage

Feedback Reference Voltage vs. Temperature

0.604

0.603

0.602

0.601

0.600

0.599

0.598

0.597

0.596

0.595

0.594

1.818

1.816

1.814

1.812

1.810

1.808

1.806

1.804

Vo=1.8V Io=2A

-60

-40

-20

0

20

40

60

80

100

120

140

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

Temperature (℃)

Input Voltage (V)

PFET Drain-Source On-State Resistance vs. Temperature NFET Drain-Source On-State Resistance vs. Temperature

75

70

65

60

55

50

45

40

35

30

25

95

90

85

80

75

70

65

60

55

50

45

-60

-40

-20

0

20

40

60

80

100

120

140

-60

-40

-20

0

20

40

60

80

100

120

140

Temperature (℃)

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March 2018

AP3445/L

Document number: DS39755 Rev. 1 - 2

AP3445/L

Performance Characteristics (@T_A= +25°C, V_IN= 5V, V_OUT= 1.8V, unless otherwise specified.)

Inductor Current Limit vs. Temperature Oscillation Frequency vs. Temperature

1200

1150

1100

1050

1000

950

6.0

5.8

5.6

5.4

5.2

5.0

4.8

4.6

4.4

4.2

4.0

3.8

3.6

3.4

900

850

800

750

700

-60

-40

-20

0

20

40

60

80

100

120

140

-40

-20

0

20

40

60

80

100

120

140

Temperature (℃)

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March 2018

AP3445/L

Document number: DS39755 Rev. 1 - 2

AP3445/L

Performance Characteristics (@T_A= +25°C, V_IN= 5V, V_OUT= 1.8V, unless otherwise specified.)

Enable Turn on Characteristic (I_OUT=2A) Enable Turn off Characteristic (I_OUT=2A)

V_EN

(5V/div)

V_EN

(5V/div)

V_OUT

(1V/div)

V_OUT

(1V/div)

V_PG

(5V/div)

V_PG

(5V/div)

I_L

(2A/div)

Output Ripple (I_OUT=0A)

Output Ripple (I_OUT=2A)

V_{OUT_AC}

(20mV/div)

V_{OUT_AC}

(20mV/div)

V_SW

(5V/div)

V_SW

(5V/div)

I_L

(2A/div)

I_L

(500mA/div)

Load Transient (I_OUT=1A to 2A)

Short Current Protection (I_OUT=2A) for AP3445L

V_{OUT_AC}

V_OUT

(20mV/div)

(1V/div)

V_PG

(5V/div)

V_SW

(5V/div)

I_L

(1A/div)

I_L

(2A/div)

Over Temperature Protection

Over Temperature Recovery

V_OUT

(1V/div)

V_OUT

(1V/div)

V_PG

(5V/div)

V_PG

(5V/div)

V_SW

(5V/div)

V_SW

(5V/div)

I_L

(2A/div)

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March 2018

AP3445/L

Document number: DS39755 Rev. 1 - 2

AP3445/L

Application Information

The AP3445/L is a 2A current mode control, synchronous buck regulator with integrated power MOSFETs. Current mode control assures

excellent line regulation, load regulation, and a wide loop bandwidth for fast response to load transients. See the typical application schematic

and functional block diagram of AP3445/L for more details. The buck controller drives the internal high side P-FETs. The buck regulator can

operate from an unregulated DC source, such as a battery, with a voltage ranging from 2.7V to 5.5V. The converter output can be regulated as

low as 0.6V to as high as V_IN. The feedback loop is compensated internally.

Under Voltage Lockout (UVLO) Circuit

When the V_INdrops lower than the UVLO detector threshold, the UVLO circuit starts to operate, V_REFstops, and high-side switch and low-side

switch built-in switch transistors turn “OFF”. As a result, V_OUTdrops according to the C_OUTcapacitance value and the load. When the V_INis rising

higher than UVLO released voltage, the IC will restart the operation.

Short Circuit Protection and Recovery

When the AP3445/L output node is shorted to GND that V_FBdrops under 0.42V, AP3445 will enter hiccup mode to protect itself and AP3445L will

enter latch-off mode. If short condition is removed, and V_FBrises over 0.42V, the AP3445 recovers to normal operation again And AP3445L will

remain in this state until VIN or EN voltage is recycled.. If the AP3445/L reaches OCP threshold while short circuit, the AP3445 will enter cycle by

cycle current limit mode until the current under OCP threshold.

Over Voltage Protection (AP3445L only)

The AP3445L has internal output OVP circuits. When VOUT is exceeds 120% of the regulation level for more than 40µs, the power switches will

be turned off. AP3445L enters latch off mode and will restart until VIN or Enable voltage recycled.

Over Temperature Protection

The internal thermal temperature protection circuitry is provided to protect the integrated circuit in the event that the maximum junction

temperature is exceeded. When the junction temperature exceeds +150°C , it shuts down the internal control circuit and switching power MOSFET.

The AP3445/L will restart automatically under the control of soft start circuit when the junction temperature decreases to +130°C .

Setting the Output Voltage

Choose R1 and R2 to program the proper output voltage. Resistor R1 is selected based on a design tradeoff between efficiency and output

voltage accuracy. For high values of R1 there is less current consumption in the feedback network. However the tradeoff is output voltage

accuracy due to the bias current in the error amplifier. Table 1 shows a list of resistors selection for common output voltages. An optional C1 of

10pF to 470pF used to boost the phase margin and improve stability. R2 in figure 6 can be determined by the following equation:

R₁ 0.6

R₂

VOUT  0.6

L1

C1

C1 (pF)

L1 (µH)

R1 (kΩ)

68kΩ

R2 (kΩ)

100kΩ

V_OUT(V)

1.0V

LX

FB

22pF

1.0µH

R1

R2

1.2V

100kΩ

150kΩ

200kΩ

317kΩ

367kΩ

1.5V

1.5 – 2.2µH

2.2µH

1.8V

2.5V

2.2µH

2.8V

Figure 1. Feedback Divider Network

Table 1. Recommended Component Selection

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March 2018

AP3445/L

Document number: DS39755 Rev. 1 - 2

AP3445/L

Application Information

Input Capacitor

The input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. The input capacitor has to

sustain the ripple current produced during the on time on the upper MOSFET. It must hence have a low ESR to minimize the losses.

The RMS current rating of the input capacitor is a critical parameter that must be higher than the RMS input current. As a rule of thumb, select an

input capacitor which has RMs rating that is greater than half of the maximum load current.

Due to large di/dt through the input capacitors, electrolytic or ceramics should be used. If a tantalum must be used, it must be surge protected.

Otherwise, capacitor failure could occur. For most applications, a 22µF ceramic capacitor is sufficient .

Output Capacitor

The output capacitor keeps the output voltage ripple small, ensures feedback loop stability and reduces the overshoot of the output voltage. The

output capacitor is a basic component for the fast response of the power supply. In fact, during load transient, for the first few microseconds it

supplies the current to the load. The converter recognizes the load transient and sets the duty cycle to maximum, but the current slope is limited

by the inductor value.

ESR of the output capacitor dominates the output voltage ripple. The amount of ripple can be calculated from the equation below:

VOUT_CAPACITOR ΔIINDUCTOR *ESR

An output capacitor with ample capacitance and low ESR is the best option. For most applications, 2x22µF ceramic capacitor will be sufficient.

ΔI

2

INDUCTOR

L(I_OUT



)

2

C_O



2

(Δ V  V_OUT)² V_OUT

Where ΔV is the maximum output voltage overshoot.

Inductor election

The inductor is used to supply smooth current to output when it is driven by a switching voltage. Its value is determined based on the operating

frequency, load current, ripple current, and duty cycle. For most application, the value of the inductor will fall in the range of 1.0mH to 2.2mH.

Choose an inductor that has small DC resistance, has enough current rating and is hard to cause magnetic saturation.

Vo

L(mH)

1.0µH

1.5 – 2.2µH

2.2µH

1.0V

1.2V

1.5V

1.8V

2.5V

2.8V

3.3V

2.2µH

Table 2: Recommended Inductor Selection Table

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March 2018

AP3445/L

Document number: DS39755 Rev. 1 - 2

AP3445/L

Ordering Information

AP3445X X - X

Packing

Version

Package

Blank : AP3445

L : AP3445L

W6 : SOT26

(SC74R)

-7 : Tape & Reel

Package

Temperature Range

Part Number

Marking ID

Packing

SOT26 (SC74R)

-40 to +85°C

AP3445W6-7

9B

9C

-7

AP3445LW6-7

Marking Information

(1) SOT26 (SC74R)

( Top View )

6

5

4

XX : Identification Code

Y : Year 0~9

XX Y W X

W : Week : A~Z : 1~26 week;

a~z : 27~52 week; z represents

52 and 53 week

1

2

3

X : Internal Code

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AP3445/L

Document number: DS39755 Rev. 1 - 2

AP3445/L

Package Outline Dimensions

Please see http://www.diodes.com/package-outlines.html for the latest version.

(1) Package Type: SOT26 (SC74R)

D

SOT26 (SC74R)

Dim Min Max

A1 0.013 0.10

A2 1.00 1.30

A3 0.70 0.80

Typ

0.05

E1

E

1.10

0.75

0.38

0.15

3.00

0.95

1.90

2.80

1.60

0.40

8°

b

c

D

e

e1

E

0.35 0.50

0.10 0.20

2.90 3.10

-

b

a1

2.70 3.00

e1

E1 1.50 1.70

L

a

a1

0.35 0.55

-

7°

A2

A1

A3

All Dimensions in mm

Seating Plane

a

L

e

c

Suggested Pad Layout

Please see http://www.diodes.com/package-outlines.html for the latest version.

(1) Package Type: SOT26 (SC74R)

C1

Dimensions Value (in mm)

C

C1

G

X

Y

2.40

0.95

1.60

0.55

0.80

3.20

Y1

G

Y

C

Y1

X

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AP3445/L

Document number: DS39755 Rev. 1 - 2

AP3445/L

IMPORTANT NOTICE

DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT,

INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

(AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).

Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes

without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the

application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or

trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume

all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated

website, harmless against all damages.

Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channel.

Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and

hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising out of, directly or

indirectly, any claim of personal injury or death associated with such unintended or unauthorized application.

Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings

noted herein may also be covered by one or more United States, international or foreign trademarks.

This document is written in English but may be translated into multiple languages for reference. Only the English version of this document is the

final and determinative format released by Diodes Incorporated.

LIFE SUPPORT

Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express

written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:

A. Life support devices or systems are devices or systems which:

1. are intended to implant into the body, or

2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the

labeling can be reasonably expected to result in significant injury to the user.

B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the

failure of the life support device or to affect its safety or effectiveness.

Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and

acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any

use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related

information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its

representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.

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AP3445/L

Document number: DS39755 Rev. 1 - 2


型号：	AP3445
厂家：	DIODES INCORPORATED
描述：	STEP-DOWN DC-DC BUCK CONVERTER
文件：	总13页 (文件大小：853K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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