Description
The DS7880 DS8880 is custom designed to decode four lines of BCD and drive a gas-filled seven-segment display tube Each output constitutes a switchable adjustable current sink which provides constant current to the tube segment even with high tube anode supply tolerance or fluctuation These current sinks have a voltage pliance from 3V to at least 80V typically the output current varies 1% for output voltage changes of 3 to 50V Each bit line of the decoder switches a current sink on or off as prescribed by the input code Each current sink is ratioed to the b-output current as required for even illumination of all segments Output currents may be varied over the 0 2 to 1 5 mA range for driving various tube types or multiplex operation The output current is adjusted by connecting an external pro- gram resistor (RP) from VCC to the Program input in accordance with the programming curve The circuit design provides a one-to-one correlation between program input current and b-segment output current The Blanking Input provides unconditional blanking of any output display while the Ripple Blanking pins allow simple leading- or trailing-zero blanking.
