High Performance Current Mode PWM Controller

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Overview

The UC3844B, UC3845B series are high performance fixed frequency current mode controllers. They are specifically designed for Off-Line and dc-to-dc converter applications offering the designer a cost-effective solution with minimal external components. These integrated circuits feature an oscillator, a temperature compensated reference, high gain error amplifier, current sensing comparator, and a high current totem pole output ideally suited for driving a power MOSFET.

Also included are protective features consisting of input and reference undervoltage lockouts each with hysteresis, cycle-by-cycle current limiting, a latch for single pulse metering, and a flip-flop which blanks the output off every other oscillator cycle, allowing output deadtimes to be programmed from 50% to 70%.

These devices are available in an 8-pin dual-in-line and surface mount (SO-8) plastic package as well as the 14-pin plastic surface mount (SO-14). The SO-14 package has separate power and ground pins for the totem pole output stage.

The UCX844B has UVLO thresholds of 16 V (on) and 10 V (off), ideally suited for off-line converters. The UCX845B is tailored for lower voltage applications having UVLO thresholds of 8.5 V (on) and 7.6 V (off).

  • Trimmed Oscillator for Precise Frequency Control
  • Oscillator Frequency Guaranteed at 250 kHz
  • Current Mode Operation to 500 kHz Output Switching Frequency
  • Output Deadtime Adjustable from 50% to 70%
  • Automatic Feed Forward Compensation
  • Latching PWM for Cycle-By-Cycle Current Limiting
  • Internally Trimmed Reference with Undervoltage Lockout
  • High Current Totem Pole Output
  • Undervoltage Lockout with Hysteresis
  • Low Startup and Operating Current
  • Pb-Free Packages are Available

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Orderable Parts:

10

Product

Status

CAD Models

Compliance

Package Type

Case Outline

MSL Type

MSL Temp (°C)

Container Type

Container Qty.

ON Target

Topology

Control Mode

fsw Typ (kHz)

Stand-by Mode

UVLO (V)

Short Circuit Protection

Latch

Soft Start

VCC Max (V)

Drive Cap. (mA)

Reference Price

UC3845BD1G

Loading...

Active

CAD Model

Pb

A

H

P

SOIC-8

1

260

TUBE

98

N

Step-Up

Current Mode

52

No

Yes

Yes

No

No

25

200 / 200

$0.2565

More Details

UC3845BD1R2G

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Active

CAD Model

Pb

A

H

P

SOIC-8

1

260

REEL

2500

N

Step-Up

Current Mode

52

No

Yes

Yes

No

No

25

200 / 200

$0.2504

More Details

UC3845BDG

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Obsolete

CAD Model

Pb

A

H

P

SOIC-14

1

260

TUBE

55

N

Step-Up

Current Mode

52

No

Yes

Yes

No

No

25

200 / 200

Price N/A

More Details

UC3845BDR2G

Loading...

Active

CAD Model

Pb

A

H

P

SOIC-14

1

260

REEL

2500

N

Step-Up

Current Mode

52

No

Yes

Yes

No

No

25

200 / 200

$0.4076

More Details

UC3845BNG

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Active

CAD Model

Pb

A

H

P

PDIP-8

NA

0

TUBE

50

N

Step-Up

Current Mode

52

No

Yes

Yes

No

No

25

200 / 200

$0.3988

More Details

UC3845BVD1G

Loading...

Obsolete

CAD Model

Pb

A

H

P

SOIC-8

1

260

TUBE

98

N

Step-Up

Current Mode

52

No

Yes

Yes

No

Yes

25

200 / 200

Price N/A

More Details

UC3845BVD1R2G

Loading...

Active

CAD Model

Pb

A

H

P

SOIC-8

1

260

REEL

2500

N

Step-Up

Current Mode

52

No

Yes

Yes

No

Yes

25

200 / 200

$0.2589

More Details

UC3845BVDG

Loading...

Obsolete

CAD Model

Pb

A

H

P

SOIC-14

1

260

TUBE

55

N

Step-Up

Current Mode

52

No

Yes

Yes

No

Yes

25

200 / 200

Price N/A

More Details

UC3845BVDR2G

Loading...

Active

CAD Model

Pb

A

H

P

SOIC-14

1

260

REEL

2500

N

Step-Up

Current Mode

52

No

Yes

Yes

No

Yes

25

200 / 200

$0.3968

More Details

UC3845BVNG

Loading...

Obsolete

CAD Model

Pb

A

H

P

PDIP-8

NA

0

TUBE

50

N

Step-Up

Current Mode

52

No

Yes

Yes

No

Yes

25

200 / 200

Price N/A

More Details

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