HIGH-PERFORMANCE CURRENT-MODE PWM CONTROLLERS
SLVS610B – AUGUST 2006 – REVISED JULY 2007
• Low Start-Up Current (<0.5 mA)
• Trimmed Oscillator Discharge Current
• Current Mode Operation to 500 kHz
• Automatic Feed-Forward Compensation
• Latching PWM for Cycle-by-Cycle Current
• Internally Trimmed Reference With
• High-Current Totem-Pole Output Undervoltage
Lockout With Hysteresis
• Double-Pulse Suppression
D (SOIC) OR P (PDIP) PACKAGE
D (SOIC) PACKAGE
8 POWER GROUND
NC − No internal connection
The TL284xB and TL384xB 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. Internally implemented circuits include an undervoltage lockout (UVLO) and a precision
reference that is 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.
The TL284xB and TL384xB series are pin compatible with the standard TL284x and TL384x with the following
improvements. The start-up current is specified to be 0.5 mA (max), while the oscillator discharge current is
trimmed to 8.3 mA (typ). In addition, during undervoltage lockout conditions, the output has a maximum
saturation voltage of 1.2 V while sinking 10 mA (VCC = 5 V).
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 TLx842B and TLx844B devices make them ideally
suited to off-line applications. The corresponding typical thresholds for the TLx843B and TLx845B devices are
8.4 V (on) and 7.6 V (off). The TLx842B and TLx843B devices can operate to duty cycles approaching 100%. A
duty-cycle range of 0% to 50% is obtained by the TLx844B and TLx845B by the addition of an internal toggle
flip-flop, which blanks the output off every other clock cycle.The TL284xB-series devices are characterized for
operation from –40°C to 85°C. The TL384xB-series devices are characterized for operation from 0°C to 70°C.
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PRODUCTION DATA information is current as of publication date.
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