Texas Instruments UC3849Q

Current Mode PWM Controller Average Secondary Side 1MHz 20V 0.3A 28-Pin PLCC
Pulse Width Modulation (PWM) Controller IC; Frequency:1000kHz; No. of Pins:28; Operating Temperature Range:0°C to 70°C; Leaded Process Compatible:No; Number of PWM Outputs:1; Output Current:250mA; Package/Case:28-PLCC ;RoHS Compliant: No
The UC3849 family of average current-mode controllers accurately accomplishes secondary side average current mode control. The secondary-side output voltage is regulated by sensing the output voltage and differentially sensing the ac switching current. The sensed output voltage drives a voltage error amplifier. The ac switching current, monitored by a current sense resistor, drives a high bandwidth, low offset current sense amplifier. The outputs of the voltage error amplifier and current sense amplifier differentially drive a high bandwidth, integrating current error amplifier. The sawtooth waveform at the current error amplifier output is the amplified and inverted inductor current sensed through the resistor. This inductor current down-slope compared to the PWM ramp achieves slope compensation, which gives an accurate and inherent fast transient response to changes in load.The UC3849 features load share, oscillator synchronization, undervoltage lockout, and programmable output control. Multiple chip operation can be achieved by connecting up to ten UC3849 chips in parallel. The SHARE bus and CLKSYN bus provide load sharing and synchronization to the fastest oscillator respectively. The UC3849 is an ideal controller to achieve high power, secondary side average current mode control.