Datasheet > UC1848_14

UC1848_14

更新时间： 2024-11-05 02:58:43

品牌	Logo	应用领域
德州仪器 - TI		/
页数	文件大小	规格书
9页	361K
描述
Average Current Mode PWM Controller

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UC1848_14 数据手册

UC1848

UC2848

UC3848

Average Current Mode PWM Controller

BLOCK DIAGRAM

FEATURES

• Practical Primary Side Control of

Isolated Power Supplies with DC

Control of Secondary Side Current

• Accurate Programmable Maximum

Duty Cycle Clamp

• Maximum Volt-Second Product Clamp

to Prevent Core Saturation

• Practical Operation Up to 1MHz

• High Current (2A Pk) Totem Pole

Output Driver

• Wide Bandwidth (8MHz) Current Error

Amplifier

• Under Voltage Lockout Monitors VCC,

VIN and VREF

• Output Active Low During UVLO

• Low Startup Current (500µA)

• Precision 5V Reference (1%)

UDG-93003-1

DESCRIPTION

The UC3848 family of PWM control ICs makes primary output driver. The current error amplifier easily interfaces

side average current mode control practical for isolated with an optoisolator from a secondary side voltage sens-

switching converters. Average current mode control in- ing circuit.

sures that both cycle by cycle peak switch current and

A full featured undervoltage lockout (UVLO) circuit is con-

maximum average inductor current are well defined and

tained in the UC3848. UVLO monitors the supply voltage

will not run away in a short circuit situation. The UC3848

to the controller (VCC), the reference voltage (VREF),

can be used to control a wide variety of converter topolo-

and the input line voltage (VIN). All three must be good

before soft start commences. If either VCC or VIN is low,

gies.

In addition to the basic functions required for pulse width

modulation, the UC3848 implements a patented tech-

nique of sensing secondary current in an isolated buck

derived converter from the primary side. A current wave-

form synthesizer monitors switch current and simulates

the inductor current down slope so that the complete cur-

rent waveform can be constructed on the primary side

without actual secondary side measurement. This infor-

mation on the primary side allows for full DC control of

output current.

the supply current required by the chip is only 500µA and

the output is actively held low.

Two on board protection features set controlled limits to

prevent transformer core saturation. Input voltage is mon-

itored and pulse width is constrained to limit the maxi-

mum volt-second product applied to the transformer. A

unique patented technique limits maximum duty cycle

within 3% of a user programmed value.

These two features allow for more optimal use of trans-

formers and switches, resulting in reduced system size

and cost.

The UC3848 circuitry includes a precision reference, a

wide bandwidth error amplifier for average current con-

trol, an oscillator to generate the system clock, latching

PWM comparator and logic circuits, and a high current

Patents embodied in the UC3848 belong to Lambda

Electronics Incorporated and are licensed for use in ap-

plications employing these devices.

4/96

12 3 4 5 6 7...9

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与UC1848_14相关器件

型号	品牌	获取价格	描述	数据表
UC1848DW	TI	获取价格	UC1848DW
UC1848J	TI	获取价格	Average Current Mode PWM Controller 16-CDIP -55 to 125
UC1848N	TI	获取价格	UC1848N
UC1848Q	TI	获取价格	UC1848Q
UC1849	TI	获取价格	Secondary Side Average Current Mode Controller
UC1849DW	ETC	获取价格	Analog IC
UC1849DWTR	ETC	获取价格	Analog IC
UC1849N	ETC	获取价格	Analog IC
UC1849PW	ETC	获取价格	Analog IC
UC1849PWTR	ETC	获取价格	Analog IC

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