1FEATURES

• Qualified for Automotive Applications

• 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

Limiting

• Internally Trimmed Reference With

Undervoltage Lockout

• High-Current Totem-Pole Output Undervoltage

Lockout With Hysteresis

• Double-Pulse Suppression

DESCRIPTION

The TL284xB 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 series are pin compatible with the standard TL284x 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 TL2842B and TL2844B devices make them ideally

suited to off-line applications. The corresponding typical thresholds for the TL2843B and TL2845B devices are

8.4 V (on) and 7.6 V (off). The TL2842B and TL2843B devices can operate to duty cycles approaching 100%. A

duty-cycle range of 0% to 50% is obtained by the TL2844B and TL2845B 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 125°C.