AS2208

The AS2208 is a simplified pulse width modulation control-ler, offering similar functionality as that of the AS3842.Based on the AS2214, the AS2208 provides the additional features of low startup current and overvoltage latching,making it a good solution for adapter applications.

The PWM function of AS2208 is controlled by the current sense com-parator for normal current mode control.  The COMP pin,which serves as an input to the current sense comparator,provides a 1 mA current source which can be tied directly to the control loop optocoupler.  The output stage is a high current totem pole output that sees only 85 ns delay from the PWM comparator.

The AS2208 requires only 100 A of startup current.  The undervoltage lockout (UVLO)thresholds are nominally 14V for turn on and 8 V for turn off.  The VREG pin, based on a trimmed bandgap reference, provides a temperature com-pensated 5 V to loads of up to 50 mA.  The oscillator discharge current is trimmed to provide guaranteed duty cycle clamping.