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UC3845DTR

更新时间： 2024-01-28 15:26:51

品牌	Logo	应用领域
德州仪器 - TI		控制器
页数	文件大小	规格书
19页	934K
描述
Current Mode PWM Controller

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数据手册

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UC3845DTR 数据手册

UC1842/3/4/5

UC2842/3/4/5

UC3842/3/4/5

Current Mode PWM Controller

FEATURES

DESCRIPTION

•

Optimized For Off-line And DC

To DC Converters

The UC1842/3/4/5 family of control ICs provides the necessary features to

implement off-line or DC to DC fixed frequency current mode control schemes

with a minimal external parts count. Internally implemented circuits include

under-voltage lockout featuring start up current less than 1mA, a precision

reference trimmed for accuracy at the error amp input, logic to insure latched

operation, a PWM comparator which also provides current limit control, and a

totem pole output stage designed to source or sink high peak current. The

output stage, suitable for driving N Channel MOSFETs, is low in the off state.

•

Low Start Up Current (<1mA)

Automatic Feed Forward

Compensation

•

Pulse-by-pulse Current Limiting

Enhanced Load Response

Characteristics

Differences between members of this family are the under-voltage lockout

thresholds and maximum duty cycle ranges. The UC1842 and UC1844 have

UVLO thresholds of 16V (on) and 10V (off), ideally suited to off-line

applications. The corresponding thresholds for the UC1843 and UC1845 are

8.4V and 7.6V. The UC1842 and UC1843 can operate to duty cycles

approaching 100%. A range of zero to 50% is obtained by the UC1844 and

UC1845 by the addition of an internal toggle flip flop which blanks the output

off every other clock cycle.

•

Under-voltage Lockout With

Hysteresis

•

Double Pulse Suppression

High Current Totem Pole

Output

•

Internally Trimmed Bandgap

Reference

•

500khz Operation

Low RO Error Amp

BLOCK DIAGRAM

A/B

Note 1:

Note 2:

A = DIL-8 Pin Number. B = SO-14 and CFP-14 Pin Number.

Toggle flip flop used only in 1844 and 1845.

SLUS223A - APRIL 1997 - REVISED MAY 2002

12 3 4 5 6 7...19

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