TL2843B

• Product Introduction

The TL284xB and TL384xB series of integrated circuits provide the necessary functionality to implement off-line or DC-to-DC fixed-frequency current-mode control schemes with a minimum number of external components. The internal implementation circuitry includes undervoltage lockout (UVLO) and a precise reference to the accuracy of the trimmed error amplifier input. Other internal circuitry includes logic to ensure lock-on operation, pulse width modulation (PWM) comparison, current limiting control, and a totem pole output stage design with high peak current at the source or sink. The output stage can drive the N-channel MOSFET to be in the off state when it is low.

The TL284xB and TL384xB series are pin-compatible with the standard TL284x and TL384x with the following improvements. The start-up current is specified at 0.5 milliamps (maximum), while the discharge current oscillates to 8.3 mA (typical). In addition, under undervoltage conditions, the output has a maximum saturation voltage of 1.2 V and a relationship of 10 mA (VCC = 5 V) signal for sinking.

The main difference between the members of these series is the UVLO threshold and the maximum duty cycle range. The 16 five (top) and 10 V (off) thresholds for the TLx842B and the typical UVLO of the TLx844B make them ideal for offline applications. The typical thresholds corresponding to TLx843B and TLx845B devices are 8.4 five (top) and 7.6 five (off). The TLx842B and TLx843B devices can work together with a duty cycle of nearly 100%. The 0% to 50% duty cycle range gets an internal trigger trigger, while blank, shutting off all other clock cycles. The output of the TL284xB series devices is characterized by a range of operating from the TLx844B and TLx845B - from 40°C to 85°C The TL384xB series devices are characterized by operating from 0°C to 70°C