DESCRIPTION
The UC3842 is available in an 8-Pin mini-DIP the necessary features to implement off-line, fixed-frequency current-mode control schemes with a minimal external parts count. This technique results in improved line regulation, enhanced load response characteristics, and a simpler, easier to design control loop. Topological advantages include inherent pulse-by-pulse current limiting.
Protection circuitry includes built-in undervoltage lock-out and current limiting. Other features include fully-latched operation, a 1% trimmed bandgap reference, and start-up current less than 1mA. These devices feature a totem-pole output designed to source and sink high peak current from a capacitive load, such as the gate of a power MOSFET. Consistent with N-channel power devices, the output is low in the OFF-state.

FEATURES
• Low start-up current (≤1mA)
• Automatic feed-forward compensation
• Pulse-by-pulse current limiting
• Enhanced load response characteristics
• Undervoltage lock-out with hysteresis
• Double pulse suppression
• High current totem-pole output
• Internally-trimmed bandgap reference
• 400kHz operation, guaranteed min

APPLICATIONS
• Off-line switched mode power supplies
• DC-to-DC converters UC3842

DESCRIPTION
The UC1842/3/4/5 family of control devices 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 1 mA, 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.
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 16 VON and 10 VOFF, ideally suited to off-line applications. The corresponding thresholds for the UC1843 and UC1845 are 8.4 V and 7.6 V. 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.

FEATURES
• Optimized For Off-line and DC-to-DC Converters
• Low Start-Up Current (<1 mA)
• Automatic Feed Forward Compensation
• Pulse-by-Pulse Current Limiting
• Enhanced Load Response Characteristics
• Under-Voltage Lockout With Hysteresis
• Double Pulse Suppression
• High Current Totem Pole Output
• Internally Trimmed Bandgap Reference
• 500-kHz Operation
• Low RO Error Amp

Description
The UC3842/UC3843/UC3844/UC3845 are fixed frequencycurrent-mode PWM controller. They are specially designed for Off-Line and DC to DC converter applications with minimum external components. These integrated circuits feature a trimmed oscillator for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator and a high current totempole output for driving a Power MOSFET. The UC3842 and UC3844 have UVLO thresholds of 16V (on) and 10V (off). The UC3843 and UC3845 are 8.5V(on) and 7.9V (off). The UC3842 and UC3843 can operate within 100% duty cycle. The UC3844 and UC3845 can operate with 50% duty cycle.

Features
• Low Start up Current
• Maximum Duty Clamp
• UVLO With Hysteresis
• Operating Frequency up to 500KHz

The UC384xB 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 a trimmed oscillator for precise DUTY CYCLE CONTROL under voltage lock out featuring start-up current less than 0.5mA, 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.

„  DESCRIPTION
The UTC UC3842B/3843Bare specifically designed for off-line and dc-to-dc converter applications offering the designer a cost-effective solution with minimal external components. The UC3842Bhas UVLO thresholds 16V (on) and 10V(off), ideally suited for off-line converters. The UC3843Bis tailored for lower voltage applications having UVLO thresholds of 8.4V(on) and 7.6V(off).

„  FEATURES
* Trimmed oscillator for precise frequency control
* Oscillator frequency guaranteed at 250kHz
* Current mode operation to 500kHz
* 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

DESCRIPTION
The UTC UC3842A/3843A provide the necessary functions to implement off-line or DC to DC fixed frequency current mode, controlled switching circuits with minimal external components.

FEATURES
* Low start up current ( Typical 0.12mA )
* Automatic feed forward compensation
* Pulse-by-Pulse current limiting
* Under-voltage lockout with hysteresis
* Double pulse Suppression
* High current totem pole output to drive MOSFET directly
* Internally trimmed band gap reference
* 500kHz operation

DESCRIPTION
The UC3842 is available in an 8-Pin mini-DIP the necessary features to implement off-line, fixed-frequency current-mode control schemes with a minimal external parts count. This technique results in improved line regulation, enhanced load response characteristics, and a simpler, easier to design control loop. Topological advantages include inherent pulse-by-pulse current limiting.
Protection circuitry includes built-in undervoltage lock-out and current limiting. Other features include fully-latched operation, a 1% trimmed bandgap reference, and start-up current less than 1mA. These devices feature a totem-pole output designed to source and sink high peak current from a capacitive load, such as the gate of a power MOSFET. Consistent with N-channel power devices, the output is low in the OFF-state.

FEATURES
• Low start-up current (≤1mA)
• Automatic feed-forward compensation
• Pulse-by-pulse current limiting
• Enhanced load response characteristics
• Undervoltage lock-out with hysteresis
• Double pulse suppression
• High current totem-pole output
• Internally-trimmed bandgap reference
• 400kHz operation, guaranteed min

APPLICATIONS
• Off-line switched mode power supplies
• DC-to-DC converters UC3842

Description
The UC3842A/UC3843A are fixed PWM controller for Off-Line and DC to DC converter applications. The internal circuits include UVLO, low start up current circuit, temperature compensated reference, high gain error amplifier, current sensing comparator, and high current totem-pole output for driving a POWER MOSFET. Also UC3842A/ UC3843A provide low start up current below 0.3mA and short shutdown delay time typ. 100ns. The UC3842A has UVLO threshold of 16V(on) and 10V(off). The UC3843A is 8.4V(on) and 7.6V(off). The UC3842A and UC3843A can operate within 100% duty cycle.

Features
• Low Start Current 0.2mA (typ)
• Operating Range Up To 500KHz
• Cycle by Cycle Current Limiting
• Under Voltage Lock Out With Hysteresis
• Short Shutdown Delay Time: typ.100ns
• High Current Totem-pole Output
• Output Swing Limiting: 22V

DESCRIPTION
The UC384xA 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 a trimmed oscillator for precise DUTY CYCLE CONTROL under voltage lockout featuring start-up current less than 0.5mA, 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.
Differences between members of this family are the under-voltage lockout thresholds and maximum duty cycle ranges. The UC3842A and UC3844A have UVLO thresholds of 16V (on) and 10V (off), ideally suited off-line applications The corresponding thresholds for the UC3843A and UC3845A are 8.5 V and 7.9V. The UC3842A and UC3843A can operate to duty cycles approaching 100%. A range of the zero to < 50 % is obtained by the UC3844A and UC3845A by the addition of an internal toggle flip flop which blanks the output off every other clock cycle.

■ TRIMMED OSCILLATOR DISCHARGE CURRENT
■ CURRENT MODE OPERATION TO 500kHz
■ 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 START-UP CURRENT (< 0.5mA)
■ DOUBLE PULSE SUPPRESSION

DESCRIPTION
The UC184xA family of control ICs provides all the necessary features to implement off-line fixed-frequency, current-mode switching power supplies with a minimum of external components. The current mode architecture demonstrates improved load regulation, pulse-by-pulse current limiting and inherent protection of the power supply output switch. The IC includes: A bandgap reference trimmed to ±1% accuracy, an error amplifier, a current sense comparator with internal clamp to 1V, a high current totem pole output stage for fast switching of power MOSFET's, and an externally programmable oscillator to set frequency and maximum duty cycle. The undervoltage lock-out is designed to operate with 250µA typ. start-up current, allowing an efficient bootstrap supply voltage design.

KEY FEATURES
■ LOW START-UP CURRENT. (0.5mA max.)
■ TRIMMED OSCILLATOR DISCHARGE CURRENT. (See Product Highlight)
■ OPTIMIZED FOR OFF-LINE AND DC-TO-DC CONVERTERS.
■ AUTOMATIC FEED FORWARD COMPENSATION.
■ PULSE-BY-PULSE CURRENT LIMITING.
■ ENHANCED LOAD RESPONSE CHARACTERISTICS.
■ UNDER-VOLTAGE LOCKOUT WITH HYSTERESIS.
■ DOUBLE PULSE SUPPRESSION.
■ HIGH-CURRENT TOTEM POLE OUTPUT.
■ INTERNALLY TRIMMED BANDGAP REFERENCE.
■ 500KHz OPERATION.
■ LOW RO ERROR AMPLIFIER.

APPLICATIONS
■ ECONOMICAL OFF-LINE FLYBACK OR FORWARD CONVERTERS.
■ DC-DC BUCK OR BOOST CONVERTERS.
■ LOW COST DC MOTOR CONTROL.

The UC3842A, UC3843A series of high performance fixed frequency current mode controllers 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 a trimmed oscillator for precise duty cycle control, 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, programmable output deadtime, and a latch for single pulse metering.
These devices are available in an 8−pin dual−in−line plastic package as well as the 14−pin plastic surface mount (SOIC−14). The SOIC−14 package has separate power and ground pins for the totem pole output stage.
The UCX842A has UYLO thresholds of 16 V (on) and 10 V (off), ideally suited for off−line converters. The UCX843A is tailored for lower voltage applications having UVLO thresholds of 8.5 V (on) and 7.6 V (off).

Features
• Trimmed Oscillator Discharge Current for Precise Duty Cycle Control
• Current Mode Operation to 500 kHz
• 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
• Direct Interface with ON Semiconductor SENSEFET™ Products
• Pb−Free Packages are Available

DESCRIPTION
The UC3842A-BW/43A-BW/44A-BW/45A-BW are fixed frequency current mode PWM controller. They are specially designed for OFF−Line and DC to DC converter applications with a minimal external components. Internally implemented circuits include a trimmed oscillator for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator, and a high current totempole output ideally suited for driving a power MOSFET. Protection circuitry includes built undervoltage lockout and current limiting.

FEATURES
• Low Start-Up and Operating Current
• High Current Totem Pole Output
• Undervoltage Lockout With Hysteresis
• Operating Frequency Up To 500KHz