UC2841

Manufacturer Part NumberUC2841
DescriptionThe UC1841 family of PWM controllers has been designed to increase the level of versatility while retaining all of the performance features of the earlier UC1840 devices
ManufacturerTexas Instruments
UC2841 datasheet
 


Specifications of UC2841

TopologyBoost, Buck, Flyback, ForwardControl MethodCurrent,Voltage
Duty Cycle(max)(%)95Frequency(max)(khz)450
Uvlo Thresholds On/off(v)8/7.8Pin/package18PDIP, 18SOIC
Vin(min)(v)8Vin(max)(v)32
Regulated Outputs(#)1Operating Temperature Range(c)-20 to 85
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Programmable, Off-Line, PWM Controller
FEATURES
All Control, Driving, Monitoring, and
Protection Functions Included
Low-current, Off-line Start Circuit
Voltage Feed Forward or Current
Mode Control
Guaranteed Duty Cycle Clamp
PWM Latch for Single Pulse per Period
Pulse-by-Pulse Current Limiting Plus
Shutdown for Over-Current Fault
No Start-up or Shutdown Transients
Slow Turn-on Both Initially and After
Fault Shutdown
Shutdown Upon Over- or
Under-Voltage Sensing
Latch Off or Continuous Retry After
Fault
PWM Output Switch Usable to 1A
Peak Current
1% Reference Accuracy
500kHz Operation
18 Pin DIL Package
BLOCK DIAGRAM
Note: Positive true logic, latch outputs high with set, reset has priority.
6/93
DESCRIPTION
The UC1841 family of PWM controllers has been designed to increase
the level of versatility while retaining all of the performance features of
the earlier UC1840 devices. While still optimized for highly-efficient boot-
strapped primary-side operation in forward or flyback power converters,
the UC1841 is equally adept in implementing both low and high voltage
input DC to DC converters. Important performance features include a
low-current starting circuit, linear feed-forward for constant volt-second
operation, and compatibility with either voltage or current mode topologies.
In addition to start-up and normal regulating PWM functions, these de-
vices include built in protection from over-voltage, under-voltage, and
over-current fault conditions with the option for either latch-off or automat-
ic restart.
While pin compatible with the UC1840 in all respects except that the po-
larity of the External Stop has been reversed, the UC1841 offers the fol-
lowing improvements:
1. Fault latch reset is accomplished with slow start discharge rather
than recycling the input voltage to the chip.
2. The External Stop input can be used for a fault delay to resist
shutdown from short duration transients.
3. The duty-cycle clamping function has been characterized and
specified.
The UC1841 is characterized for -55°C to +125°C operation while the
UC2841 and UC3841 are designed for -25°C to +85°C and 0°to +70°C,
respectively.
UC1841
UC2841
UC3841

UC2841 Summary of contents

  • Page 1

    ... The External Stop input can be used for a fault delay to resist shutdown from short duration transients. 3. The duty-cycle clamping function has been characterized and specified. The UC1841 is characterized for -55°C to +125°C operation while the UC2841 and UC3841 are designed for -25°C to +85°C and 0°to +70°C, respectively. UC1841 UC2841 UC3841 ...

  • Page 2

    ... C CONNECTION DIAGRAMS DIL-18, SOIC-18 (TOP VIEW Package ELECTRICAL CHARACTERISTICS: UC1841, -25°C to +85°C for the UC2841, and 0°C to +70°C for the UC3841 .001mfd, Current Limit Threshold = 200mV PARAMETER Power Inputs Start-Up Current ...

  • Page 3

    ... ELECTRICAL CHARACTERISTICS: UC1841, -25°C to +85°C for the UC2841, and 0°C to +70°C for the UC3841 .001mfd, Current Limit Threshold = 200mV PARAMETER Ramp Generator Ramp Current, Minimum I SENSE Ramp Current, Maximum I SENSE Ramp Valley Ramp Peak Clamping Level Error Amplifier ...

  • Page 4

    ... A hysteresis current. input voltage reaches start threshold. increase of output pulse width > 3.2V (typically 3V) b. Stop > 2.4V (typically 1.6V) c. Current Sense 400mV over threshold (typical). rises above threshold. Error Latch. typical delay of 13ms UC1841 UC2841 UC3841 and sense voltage ...

  • Page 5

    ... Start/UV Hysteresis Oscillator Frequency Error Amplifier Open Loop Gain and Phase PWM Output-Saturation Voltage PWM Output Minimum Pulse Width Shutdown Timing 5 UC1841 UC2841 UC3841 ...

  • Page 6

    ... PIC661 power switch, this circuit has full fault protection and high speed dynamic line regulation due to its feed- forward capability. An additional feature is the ability to 6 UC1841 UC2841 UC3841 Current Limit = 200mV Current Fault Voltage = 600mV Duty Cycle Clamp = 50% = 32V ...

  • Page 7

    ... Figure A. UC1841 Programmable PWM Controller In A Simplified Flyback Regulator Figure B. Overall Schematic For A 300 Watt, Off-line Power Converter Using The UC3841 For Control 7 UC1841 UC2841 UC3841 ...

  • Page 8

    ... The minimum ramp current is REF IN SENSE l MIN The threshold where 5. Above the threshold, the ramp current will be VARIAB UC1841 UC2841 UC3841 (not shown begins to add extra ramp current is 5.6 5 ...

  • Page 9

    ... CDIP UC1841L OBSOLETE LCCC UC1841L883B OBSOLETE LCCC UC2841DW ACTIVE SOIC UC2841DWG4 ACTIVE SOIC UC2841J OBSOLETE CDIP UC2841N ACTIVE PDIP UC2841NG4 ACTIVE PDIP UC3841DW ACTIVE SOIC UC3841DWG4 ACTIVE SOIC UC3841J OBSOLETE CDIP UC3841N ACTIVE PDIP UC3841NG4 ACTIVE PDIP (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs ...

  • Page 10

    Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be ...

  • Page 11

    ... Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’ ...