FAC2596DD5.0R [FS]

3A 150KHZ PWM Buck DC/DC Converter;


型号：	FAC2596DD5.0R
厂家：	First Silicon Co., Ltd
描述：	3A 150KHZ PWM Buck DC/DC Converter
文件：	总16页 (文件大小：789K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

SEMICONDUCTOR

FAC2596

TECHNICAL DATA

General Description

Features

The FAC2596 is a series of easy to use fixed and• 3.3V, 5V and adjustable output versions

adjustable step- down (buck) switch- mode voltage• Output adjustable from 1.23v to 43V

regulators. These devices are available in fixed • Fixed 150KHz frequency internal oscillator

output voltage of 3.3V, 5V, and an adjustable • Guaranteed 3A output load current

output version. Both versions are capable of • Input voltage range up to 45V

driving a 3A load with excellent line and load • Low power standby mode, I_Qtypically 80 µA

regulation.

•

TTL shutdown capability

Excellent line and load regulation

Requires only 4 external components

Requiring

minimum number of external

components, these regulators are simple to use • High efficiency

and include internal frequency compensation, and • Thermal shutdown and current limit protection

a fixed- frequency oscillator.

•

Available in TO- 220B/TO220 and TO- 263

packages

The output voltage is guaranteed to ± 3%

tolerance under specified input voltage and

output load conditions. The oscillator frequency is

guaranteed to ± 15%. External shutdown is

included, featuring typically 80 µA standby current.

Self protection features include a two stage

frequency reducing currentlimit for the output

switch and an over temperature shutdown for

complete protection under fault conditions.

Applications

•

Simple High- efficiency step- down regulator

On- card switching regulators

Positive to negative converter

LCD monitor and LCD TV

DVD recorder and PDP TV

Battery charger

Step- down to 3.3V for microprocessors

The FAC2596 is available in TO- 220B- 5L

TO220- 5L and TO- 263- 5L packages.

Package Types

TO263- 5L

TO220B- 5L

TO220- 5L

Figure 1. Package Types of FAC2596

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FAC2596

Pin Descriptions

Pin Assignments

5 ON/OFF

4 Feedback

3 Gnd

2 Output

1 Vin

Name

Vin

Description

Input supply voltage

Switching output

Ground

Output

Gnd

TO220B- 5L/TO220- 5L

5 ON/OFF

4 Feedback

3 Gnd

2 Output

1 Vin

Feedback

ON/OFF

Output voltage feedback

ON/OFF shutdown

Active is “ Low” or floating

TO263- 5L

Ordering Information

FAC2596

Packing

Blank: Tube

Circuit Type

Package

Type and Reel

Output Versions

AD: Adjustable Output

T: TO220B- 5L

DD: TO263- 5L

P: TO220- 5L

3.3:

5.0:

Fixed Output 3.3V

Fixed Output 5V

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FAC2596

Figure 2. Functional Block Diagram of FAC2596

Typical Application (Fixed Output Voltage Versions)

A 2

Figure 3. Typical Application of FAC2596

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FAC2596

Absolute Maximum Ratings

Note1: Stresses greater than t hose listed under Maximum Ratings may cause permanent damage to the

device. This is a stress rating only and functional operation of the device at these or any other conditions

above those indicated in the operation is not implied. Exposure to absolute maximum rating conditions

for extended periods may affect reliability.

Parameter

Value

- 0.3 to 45

- 0.3 to Vin+0.3

- 1

Unit

Supply Voltage Vin

Feedback VFB pin voltage

ON/OFF Pin voltage

Output pin voltage

Output Voltage to Ground (Steady State)

Power Dissipation

Internally limited

- 40 to +125

- 65 to +150

200

Operating Temperature Range

Storage Temperature

ºC

Lead Temperature (Soldering, 10 sec)

ESD(HM)

ºC

2000

Thermal Resistance-Junction to Ambient(RθJA)

Thermal Resistance-Junction to Case(RθJC)

ºC / W

Electrical Characteristics (All Output Voltage Versions)

Unless otherwise specified, Vin = 12V for 3.3V, 5V, adjustable version. Iload = 0.5A, Ta = .25 ℃

Symbol

I_b

Parameter

Conditions

Min.

Typ.

Max.

50/100

Unit

Feedback bias current

Quiescent current

Adjustable only, V =1.3V

I_Q

V =12V force driver off

Standby quiescent current

Oscillator frequency

Saturation voltage

Current Limit

I_STBY

F_OSC

V_SAT

I_CL

ON/OFF=5V, V =36V

200/ 250 uA

127

150

1.2

4.5

173

1.4/ 1.5

5.5/6.5

KHz

I_OUT=3A

Peak Current (V_FB=0V)

Output leakage current

ON/OFF pin logic input

Output=0V (V =12V)

I_L

Output=- 1V (V_IN=36V)

Low (Regulator ON)

V_IL

1.3

0.6

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FAC2596

V_IH

Threshold voltage

High (Regulator OFF)

V_LOGIC=2.5V(Regulator OFF)

V_LOGIC=0.5V(Regulator ON)

2.0

1.3

I_H

I_L

ON/OFF pin input current

0.02

Thermal Resistance

Junction to Case

Thermal Resistance

Junction to Ambient

(Note1)

TO220B- 5L/TO220- 5L

TO263- 5L

2.5

3.5

^OC/W

θ_JC

θ_JA

TO220B- 5L/TO220- 5L

TO263- 5L

^OC/W

11V≤V_IN≤45V, 0.2A≤I_LOAD

≤

1.193/

1.180

1.267/

1.280

Vout: Output Voltage

η: Efficiency

1.23

FAC2596

ADJ

3A, V_OUTfor 9V

V_IN=12V,V_OUT=9V,I_LOAD=3A

4.75V≤V_IN≤45V, 0.2A≤I_LOAD

≤3A

3.168/

3.135

3.432/

3.465

Vout: Output Voltage

η: Efficiency

3.3

FAC2596

3.3V

V_IN=12V, I_LOAD=3A

7V≤V_IN≤45V, 0.2A≤I_LOAD

≤

4.800/

4.750

5.200/

5.250

Vout: Output Voltage

η: Efficiency

5.0

FAC2596

V_IN=12V, I_LOAD=3A

Specifications with boldface type are for full operationg temperature range, the other type are for

T_J=25^OC.

Note1: Thermal resistance with copper area of approximately 3. in²

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FAC2596

Typical Performance Characteristics

Figure 4. Output Voltage vs. Temperature Figure 5. Switching Frequency vs. Temperature

Figure 6. Output Saturation Characteristics Figure 7. Quiescent Current vs. Temperature

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FAC2596

Figure 8. ON/OFF Pin Voltage

Figure 9. ON/OFF Pin Sink Current

Figure 10. Output Saturation Characteristics

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FAC2596

Typical Application Circuit (3.3V Fixed Output Voltage Version)

Figure 11. Typical Application of FAC2596 For 3.3V

Output Capacitor (Cout)

Input Voltage

Inductor (L1)

Through Hole Electrolytic

470uf/25V

Surface Mount Tantalum

330uf/6.3V

6V ~ 18V

6V ~ 45V

47uh

68uh

560uf/25V

330uf/6.3V

Table 1. FAC2596 Series Buck Regulator Design Procedure For 3.3V

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FAC2596

Typical Application Circuit (5V Fixed Output Voltage Version)

FAC2596-5V

Figure 12. Typical Application of FAC2596 For 5V

Output Capacitor (Cout)

Input Voltage

Inductor (L1)

Through Hole Electrolytic

330uf/25V

Surface Mount Tantalum

220uf/10V

8V ~ 18V

8V ~ 45V

33uh

47uh

470uf/25V

330uf/10V

Table 2. FAC2596 Series Buck Regulator Design Procedure For 5V

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FAC2596

Typical Application Circuit (Adjustable Output Voltage Version)

FAC2596-AD

Figure 13. Typical Application of FAC2596 For ADJ

Vout

3.3V

12V

Cf (Operational)

2.7K

11K

43K

13K

1.6K

3.6K

6.8K

1.5K

33nf

10nf

1.5nf

1nf

Table 3. Vout VS. R1,R2, Cf Select Table

Output

Voltage

3.3V

Input

Voltage

Output Capacitor (Cout)

Through Hole Electrolytic

470uf/25V

Inductor (L1)

6V ~ 18V

6V ~ 45V

8V ~ 18V

8V ~ 45V

12V ~ 18V

12V ~ 45V

15V ~ 18V

15V ~ 45V

47uh

68uh

33uh

47uh

560uf/25V

330uf/25V

470uf/25V

330uf/25V

470uf/25V

220uf/25V

330uf/25V

12V

Table 4. Typical Application Buck Regulator Design Procedure

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FAC2596

(TO- 220B/TO- 220 package) operating as a buck

Function Description

switching regulator in an ambient temperature of

25^oC (still air). These temperature rise numbers

are all approximate and there are many factors

that can affect these temperatures. Higher

ambient temperatures require more heat sinking.

Pin Functions

+V_IN

This is the positive niput supply for the IC

switching regulator. A suitable input bypass

capacitor must be present at this pin to minimize

voltage transients and to supply the switching

currents needed by the regulator

The TO- 263 surface mount package tab is

designed to be soldered to the copper on a

printed circuit board.The copper and the board

are the heat sink for this package and the other

heat producing componentss, uch as the catch

diode and inductor. The PC board copper area

that the package is soldered to should be at least

Ground

Circuit ground.

0.4 in , and ideally should have 2 or more square

Output

inches of 2 oz. Additional copper area improves

the thermal characteristics, but with copper areas

greater than approximately 6 in,²only small

improvements in heat dissipation are realized. If

further thermal improvements are needed, double

sided, multilayer PC board with large copper

areas and/or airflow are recommended.

Internal switch. The voltage at this pin switches

between (+V – V_SAT) and approximately – 0.5V,

with a duty cycle of approximately V_OUT/ V . To

minimize coupling to sensitive circuitry, the PC

board copper area connecetd to this pin should

be kept a minimum.

Feedback

The FAC2596 (TO- 263 package) junction

temperature rise above ambient temperature with

a 3A load for various input and output voltages.

This data was taken with the circuit operating as a

buck switching regulator with all components

mounted on a PC board to simulate the junction

temperature under actual operating conditions.

This curve can be used for a quick check for the

approximate junction temperature for various

conditions, but be aware that there are many

factors that can affect the junction temperature.

When load currents higher than 3A are used,

double sided or multilayer PC boards with large

copper areas and/or airflow might be needed,

especially for high ambient temperatures and

high output voltages.

Senses the regulated output voltage to complete

the feedback loop.

ON/OFF

Allows the switching regulator circuit to be

shutdown using logic level signals thus dropping

the total input supply current to approximately

80uA. Pulling this pin below a threshold voltage of

approximately 1.3V turns the regulator on, and

pulling this pin above 1.3V (up to a maximum of

25V) shuts the regulatordown. If this shutdown

feature is not needed, the ON /OFF pin can be

wired to the ground pin or it can be left open, in

either case the regulator will be in the ON

condition.

Thermal Considerations

For the best thermal performance, wide copper

traces and generous amounts of printed circuit

board copper should be used in the board layout.

(Once exception to this is the output (switch) pin,

which should not have large areas of copper.)

Large areas of copper provide the best transfer of

heat (lower thermal resistance) to the surrounding

air, and moving air lowers the thermal resistance

even further.

The FAC2596 is available in two packages, a 5- pin

TO- 220B/TO- 220 and a 5- pin surface mount

TO- 263.

The TO- 220B/TO- 220 package needs a heat sink

under most conditions. The size of the heatsink

depends on the input voltage, the output voltage,

the load current and the ambient temperature.

The junction temperature rises above

Setting the Output Voltage

ambient temperature for a 3A load and different

input and output voltage.s The data for these

The output voltage is set using a resistive

voltage divider from the output voltage to

FB(FAC2596- ADJ) The voltage divider divides the

curves

was

taken

with

the

FAC2596

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FAC2596

output voltage down by the ratio:

VFB = VOUT * R2 / (R1 + R2)

Thus the output voltage is:

VOUT = 1.222 * (R1 + R2) / R2

R2 can be as high as 100KΩ, but a typical

value is 10KΩ. Using that value, R1 is

determined by:

R1 ~= 8.18 * (VOUT – 1.222) (KΩ)

For example, for a 3.3V output voltage, R2 is

10KΩ, and R1 is 17KΩ .

1/2 of the DC load current.

For insuring stable operation should be

placed as close to the IC as possible.

Alternately a smaller high quality ceramic

0.1μF capacitor may be placed closer to the IC

and a larger capacitor placed further away. If

using this technique, it is recommended that

the larger capacitor be a tantalum or

electrolytic type. All ceramic capacitors should

be places close to the FAC2596.

Output Capacitor

Inductor

The output capacitor is required to maintain

the DC output voltage. Low ESR capacitors

are preferred to keep the output voltage ripple

low. The characteristics of the output

capacitor also affect the stability of the

regulation control system. Ceramic, tantalum,

or low ESR electrolytic capacitors are

recommended. In the case of ceramic

capacitors, the impedance at the switching

frequency is dominated by the capacitance,

and so the output voltage ripple is mostly

independent of the ESR . The output voltage

ripple is estimated to be:

VRIPPLE ~= 1.4 * VIN * (fLC/fSW)^2

Where VRIPPLE is the output ripple voltage, VIN

is the input voltage,fLC is the resonant

frequency of the LC filter, fSW is the switching

frequency. In the case of tanatalum or low-

ESR electrolytic capacitors, the ESR

dominates the impedance at the switching

frequency, and so the output ripple is

calculated as:

The inductor is required to supply constant

current to the output load while being driven by

the switched input voltage. A larger value

inductor results in less ripple current that in

turn results in lower output ripple voltage.

However, the larger value inductor has a larger

physical size, higher series resistance, and/or

lower saturation current. Choose an inductor

that does not saturate under the worst- case

load conditions. A good rule for determining

the inductance is to allow the peak- to- peak

ripple current in the inductor to be approximately

30% of the maximum load

current. Also, make sure that the peak

inductor current (the load current plus half the

peak- to- peak inductor ripple current) is below

the TBDA minimum current limit. The

inductance value can be calculated by the

equation:

L = (VOUT) * (VIN-VOUT) / VIN * f * ΔI

Where VOUT is the outputvoltage, VIN is the

input voltage, f is the switching frequency, and

ΔI is the peak- to- peak inductor ripple current.

VRIPPLE ~= ΔI * RESR

Where VRIPPLE is the output voltage ripple, ΔI is

the inductor ripple current, and RESR is the

equivalent series resistance of the output

capacitors.

Input Capacitor

The input current to the step- down converter is

discontinuous, and so a capacitor is required

to supply the AC current to the step- down

converter while maintaining the DC input

voltage. A low ESR capacitor is required to

keep the noise at the IC to a minimum.

Ceramic capacitors are preferred, but tantalum

or low- ESR electrolytic capacitors may also

suffice.

Output Rectifier Diode

The output rectifier diode supplies the current

to the inductor when the high- side switch is off.

To reduce losses due to the diode forward

voltage and recovery times, use a Schottky

rectifier.

Table 1 provides the Schottky rectifier part

numbers based on the maximum input voltage

and current rating.

Choose a rectifier who’s maximum reverse

voltage rating is greater than the maximum

input voltage, and who’s current rating is

greater than the maximum load current.

The input capacitor value should be greater

than 10μF. The capacitor can be electrolytic,

tantalum or ceramic. However since it absorbs

the input switching current it requires an

adequate ripple current rating. Its RMS current

rating should be greater than approximately

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FAC2596

P_{total _loss}= V _IN× I_IN– V _O× I_O

Over Current Protection (OCP)

The power dissipation of inductor can be

approximately calculated by output current and

DCR of inductor.

The cycle by cycle current limit threshold is set

between 4A and 5A. When the load current

reaches the current limit threshold, the cycle by

cycle current limit circuit turns off the high side

switch immediately to terminate the current duty

cycle. The inductor current stops rising. The cycle

by cycle current limit protection directly limits

inductor peak current. The average inductor

current is also limited due to the limitation on peak

inductor current. When the cycle by cycle current

limit circuit is triggered, the output voltage drops

as the duty cycle is decreasing.

P_inductor_loss= I_O²× R_inductor× 1.1

The junction to ambient temperature can be got

from power dissipation in the FAC2596 and thermal

impedance from junction to ambient.

T _(jun-amb)=(P_totalloss–P_inductorloss)× Θ_JA

The maximum junction temperature of FAC2596 is

145°C, which limits the maximum load current

capability. Please seethe thermal de- rating

curves for the maximum load current of the

FAC2596 under different ambient temperatures.

The thermal performance of the FAC2596 is trongly

affected by the PCB layout. Extra care should be

taken by users during the design process to nsure

that the IC will operate under the recommended

environmental conditions.

Several layout tips are listed below for the best

electric and thermal performance.

1. Do not use thermal relief connection to the VIN

and the GND pin. Pour a maximized copper area

to the GND pin and the VIN pin to help thermal

dissipation.

2. Input capacitor should be connected to the VIN

pin and the GND pin as close as possible.

3. Make the current trace from VOUT pins to L to

the GND as short as possible.

4. Pour copper plane on all unused board area

and connect it to stable DC nodes, like VIN, GND,

or VOUT.

Thermal Management and Layout

Consideration

In the FAC2596 buck regulator circuit, high pulsing

current flows through two circuit loops. The first

loop starts from the input capacitors, to the VIN

pin, to the VOUT pins, to the filter inductor, to the

output capacitor and load,and then returns to the

input capacitor through ground.

Current flows in the first loop when the high side

switch is on. The second loop starts from the

inductor, to the output capacitors and load, to the

GND pin of the FAC2596, and to the VOUT pins of

the FAC2596. Current flows in the second loop

when the low side diode is on.

In PCB layout, minimizing the two loops area

reduces the noise of this circuit and improves

efficiency. A ground plane is recommended to

connect input capacitor, output capacitor, and

GND pin of the FAC2596.

In the FAC2596 buck regulator circuit, the two

major power dissipating components are the

FAC2596 and output inductor. The total power

dissipation of convertecrircuit can be measured

by input power minus output power.

5. Keep sensitive signal traces such as trace

connecting FB pin away from the VOUT pins.

Package Information (TO220B- 5L)

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FAC2596

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FAC2596

Package Information (TO220- 5L)

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FAC2596

Package Information (TO263- 5L)

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FAC2596DD5.0R [FS]

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