The TL284x and TL384x series of control integrated circuits provide the features that are necessary to implement off-line or dc-to-dc fixed-frequency current-mode control schemes, with a minimum number of external components. Some of the internally implemented circuits are an undervoltage lockout (UVLO), featuring a start-up current of less than 1 mA, and a precision reference trimmed for accuracy at the error amplifier input. Other internal circuits include logic to ensure latched operation, a pulse-width modulation (PWM) comparator (that 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 when it is in the off state.
Major differences between members of these series are the UVLO thresholds and maximum duty-cycle ranges.Typical UVLO thresholds of 16 V (on) and 10 V (off) on the TLx842 and TLx844 devices make them ideally suited to off-line applications. The corresponding typical thresholds for the TLx843 and TLx845 devices are 8.4 V (on)
and 7.6 V (off). The TLx842 and TLx843 devices can operate to duty cycles approaching 100%. A duty-cycle range of 0 to 50% is obtained by the TLx844 and TLx845 by the addition of an internal toggle flip-flop, which blanks the output off every other clock cycle.
The TL284x-series devices are characterized for operation from –40°C to 85°C. The TL384x-series devices are characterized for operation from 0°C to 70°C.
·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
·Undervoltage Lockout With Hysteresis
·Double-Pulse Suppression
·High-Current Totem-Pole Output
·Internally Trimmed Bandgap Reference
·500-kHz Operation
·Error Amplifier With Low Output Resistance
·Designed to Be Interchangeable With UC2842 and UC3842 Series
Feature
- 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
- Undervoltage Lockout With Hysteresis
- Double-Pulse Suppression
- High-Current Totem-Pole Output
- Internally Trimmed Bandgap Reference
- 500-kHz Operation
- Error Amplifier With Low Output Resistance
- Designed to be Interchangeable with UC2842 and UC3842 Series
The TL284x and TL384x series of control integrated circuits provide the features that are necessary to implement off-line or DC-to-DC fixed-frequency current-mode control schemes, with a minimum number of external components. Some of the internally implemented circuits are an undervoltage lockout (UVLO), featuring a start-up current of less than 1 mA, and a precision reference trimmed for accuracy at the error amplifier input. Other internal circuits include logic to ensure latched operation, a pulse-width modulation (PWM) comparator (that 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 when it is in the off state.
(Picture: Pinout)
