LA5771 [ONSEMI]

Separately-excited Step-down Switching Regulator (3.3V); 励降压开关稳压器（ 3.3V ）


型号：	LA5771
厂家：	ONSEMI
描述：	Separately-excited Step-down Switching Regulator (3.3V) 励降压开关稳压器（ 3.3V ）稳压器开关
文件：	总5页 (文件大小：76K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

Ordering number : EN8273A

Monolithic Linear IC

Separately-excited Step-down

Switching Regulator (3.3V)

LA5771MP

Overview

The LA5771MP is a separately-excited step-down switching regulator (3.3V).

Features

• High efficiency

• Four external parts

• Time-base generator (160kHz) incorporated

• Current limiter incorporated

• Thermal shutdown circuit incorporated

• Soft start circuit incorporated

Specifications

Absolute Maximum Ratings at Ta = 25°C

Parameter

Symbol

Conditions

Ratings

Unit

Input voltage

IN max

max

Output current

SW pin application reverse voltage

Allowable power dissipation

Operating temperature

Vsw

-1

Pd max

Topr

Mounted on the specified board *

3.9

°C

-30 to +125

-40 to +150

Storage temperature

Tstg

* Mounted on a specified board: 114.3mm×76.1mm×1.6mm, Copper foil ratio 60% FR4

Recommended Operating Conditions at Ta = 25°C

Parameter

Input voltage range

Symbol

Conditions

Ratings

Unit

5.5 to 28

Any and all SANYO Semiconductor Co.,Ltd. products described or contained herein are, with regard to

"standard application", intended for the use as general electronics equipment (home appliances, AV equipment,

communication device, office equipment, industrial equipment etc.). The products mentioned herein shall not be

intended for use for any "special application" (medical equipment whose purpose is to sustain life, aerospace

instrument, nuclear control device, burning appliances, transportation machine, traffic signal system, safety

equipment etc.) that shall require extremely high level of reliability and can directly threaten human lives in case

of failure or malfunction of the product or may cause harm to human bodies, nor shall they grant any guarantee

thereof. If you should intend to use our products for applications outside the standard applications of our

customer who is considering such use and/or outside the scope of our intended standard applications, please

consult with us prior to the intended use. If there is no consultation or inquiry before the intended use, our

customer shall be solely responsible for the use.

Specifications of any and all SANYO Semiconductor Co.,Ltd. products described or contained herein stipulate

the performance, characteristics, and functions of the described products in the independent state, and are not

guarantees of the performance, characteristics, and functions of the described products as mounted in the

customer's products or equipment. To verify symptoms and states that cannot be evaluated in an independent

device, the customer should always evaluate and test devices mounted in the customer

's products or

equipment.

13107 MS IM B8-8794 No.8273-1/5

LA5771MP

Electrical Characteristics at Ta = 25°C

Ratings

typ

Parameter

Symbol

Conditions

Unit

min

3.17

max

3.43

Output voltage

Efficiency

=15V, I =1.0A

3.30

=15V, I =1.0A

Switching frequency

=15V, I =1.0A

128

160

192

kHz

mV/°C

Line regulation

∆VOLINE

∆VOLOAD

∆VO/∆Ta

RREJ

=8 to 20V, I =1.0A

Load regulation

=15V, I =0.5 to 1.5A

Output voltage temperature coefficient

Ripple attenuation factor

Designeed target value*

F=100 to 120Hz

±0.5

Current limiter operating voltage

Thermal shutdown operating temperature

Thermal shutdown hysteresis width

* Designed target value: No measurement made.

=15V

3.1

TSD

Designed target value*

165

°C

∆TSD

°C

Package Dimensions

unit : mm (typ)

3275

Pd max - Ta

4.5

Mounted on a specified board:

114.3mm×76.1mm×1.6mm,

Copper foil ratio 60% FR4

4.5

10.0

1.3

4.0

3.90

3.5

3.0

2.5

2.0

1.5

1.0

0.5

(1.6)

0.9

1.7

0.2

2.7

0.4

-30

100

120

140

160

SANYO : SMP5

Ambient temperature, Ta - °C

ILA07131

Pin Assignment

cVIN dSWOUT eGND fVOS gSS

No.8273-2/5

LA5771MP

Block Diagram

2 SWOUT

Reg.

OSC

OCP

Reset

Drive

Comp.

Amp.

TSD

4 VOS

VREF

5 SS

3 GND

Application Circuit Example

SWOUT

LA5771MP

C1: 220µF/35V

C2: 1000µF/6.3V

C3: 1µF/50V

D1: SBD

VOS

GND

L1: 68µH

Notes: C3 is for the soft start function. Delete C3 and keep the SS pin open when the soft function is not necessary.

No.8273-3/5

LA5771MP

Description of Functional Settings

1.Start delay function

The SS pin has the internally-connected 22µA (typ) constant-current supply. When the voltage of SS pin exceeds the

threshold voltage, the regulator starts operation. As the threshold is 0.62V(typ), the start delay time can be calculated

as follows:

ex. For setting at 1µF

C×V 1µΑ×0.62V

Td =

=28.2ms

22µΑ

2.Soft start function

The internal PWM waveform has the voltage value as shown in the right.

1.5V

If down-conversion from the voltage of V =15V to 3.3V output is to be made,

for example, the PWM-ON duty has the value as shown below.

0.62V

PWM wave

OUT

-Vsat + VF

PWMduty=

=23%

(Note that calculation is made with Vsat=1V and VF=0.2V)

The output voltage of error amplifier, which is 3.3V, is the value with PWM=23%, as calculated in the above equation,

so that this voltage is determined as follows:

Ver=(∆VPWM)×PWMduty+VPWML=0.88V×0.23+0.62V=0.82V

(∆VPWM is the PWM amplitude value or 0.88V(typ) while VPWML is the lower limit voltage of PWM

waveform or 0.62V(typ))

SS pin and error amplifier output voltages are designed to prefer the lower voltages, so that V

OUT

will reach the

designed regulation voltage in timing when the SS pin voltage exceeds the error amplifier output. Therefore, the soft strt

time is calculated as follows:

C×∆VPWM×PWMduty C×0.88V×PWMduty

Tss =

22µA

For the set conditions of C=1µF and PWMduty=23%:

1µΑ×0.88V×0.23

Tss=

=9.2ms

22µA

No.8273-4/5

LA5771MP

Timing Chart

SWOUT

OUT

Tss

SANYO Semiconductor Co.,Ltd. assumes no responsibility for equipment failures that result from using

products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition

ranges, or other parameters) listed in products specifications of any and all SANYO Semiconductor Co.,Ltd.

products described or contained herein.

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semiconductor products fail or malfunction with some probability. It is possible that these probabilistic failures or

malfunction could give rise to accidents or events that could endanger human lives, trouble that could give rise

to smoke or fire, or accidents that could cause damage to other property. When designing equipment, adopt

safety measures so that these kinds of accidents or events cannot occur. Such measures include but are not

limited to protective circuits and error prevention circuits for safe design, redundant design, and structural

design.

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product/technology improvement, etc. When designing equipment, refer to the "Delivery Specification" for the

SANYO Semiconductor Co.,Ltd. product that you intend to use.

Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed

for volume production.

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intellctual property rights which has resulted from the use of the technical information and products mentioned

above.

This catalog provides information as of January, 2007. Specifications and information herein are subject

to change without notice.

No.8273-5/5

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