UC3845B Series

High Performance Current Mode PWM Controller

Catalog

High Performance Current Mode PWM Controller

Part	Topology	Control Features	Operating Temperature [Max]	Operating Temperature [Min]	Supplier Device Package	Voltage - Supply (Vcc/Vdd) [Min]	Voltage - Supply (Vcc/Vdd) [Max]	Number of Outputs	Output Type	Duty Cycle (Max) [Max]	Output Phases	Mounting Type	Package / Case	Package / Case [y]	Package / Case [x]	Output Configuration	Function	Package / Case	Package / Case
ON Semiconductor UC3845BD1	Boost Flyback	Frequency Control	70 °C	0 °C	8-SOIC	7.6 V	30 V	1	Transistor Driver	48 %	1	Surface Mount	8-SOIC	3.9 mm	0.154 in	Isolation Capable Positive	Step-Up Step-Up/Step-Down
ON Semiconductor UC3845BVD1R2	Boost Flyback	Frequency Control	105 °C	-40 °C	8-SOIC	7.6 V	30 V	1	Transistor Driver	48 %	1	Surface Mount	8-SOIC	3.9 mm	0.154 in	Isolation Capable Positive	Step-Up Step-Up/Step-Down
ON Semiconductor UC3845BDR2	Boost Flyback	Frequency Control	70 °C	0 °C		7.6 V	30 V	1	Transistor Driver	48 %	1	Surface Mount	14-SOIC	3.9 mm	0.154 in	Isolation Capable Positive	Step-Up Step-Up/Step-Down
ON Semiconductor UC3845BVD	Boost Flyback	Frequency Control	105 °C	-40 °C		7.6 V	30 V	1	Transistor Driver	48 %	1	Surface Mount	14-SOIC	3.9 mm	0.154 in	Isolation Capable Positive	Step-Up Step-Up/Step-Down
ON Semiconductor UC3845BN	Boost Flyback	Frequency Control	70 °C	0 °C	8-PDIP	7.6 V	30 V	1	Transistor Driver	48 %	1	Through Hole	8-DIP			Isolation Capable Positive	Step-Up Step-Up/Step-Down	0.3 in	7.62 mm
ON Semiconductor UC3845BVN	Boost Flyback	Frequency Control	105 °C	-40 °C	8-PDIP	7.6 V	30 V	1	Transistor Driver	48 %	1	Through Hole	8-DIP			Isolation Capable Positive	Step-Up Step-Up/Step-Down	0.3 in	7.62 mm
ON Semiconductor UC3845BVD1R2G	Boost Flyback	Frequency Control	105 °C	-40 °C	8-SOIC	7.6 V	30 V	1	Transistor Driver	48 %	1	Surface Mount	8-SOIC	3.9 mm	0.154 in	Isolation Capable Positive	Step-Up Step-Up/Step-Down
ON Semiconductor UC3845BVDR2G	Boost Flyback	Frequency Control	105 °C	-40 °C		7.6 V	30 V	1	Transistor Driver	48 %	1	Surface Mount	14-SOIC	3.9 mm	0.154 in	Isolation Capable Positive	Step-Up Step-Up/Step-Down
ON Semiconductor UC3845BD	Boost Flyback	Frequency Control	70 °C	0 °C		7.6 V	30 V	1	Transistor Driver	48 %	1	Surface Mount	14-SOIC	3.9 mm	0.154 in	Isolation Capable Positive	Step-Up Step-Up/Step-Down
ON Semiconductor UC3845D			70 °C	0 °C								Surface Mount	14-SOIC	3.9 mm	0.154 in

Catalog

High Performance Current Mode PWM Controller

Key Features

• 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

Description

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).