The UCC3750 Source Ringer Controller provides a complete control and drive solution for a four quadrant flyback-based ring generator circuit. The IC controls a primary side switch, which is modulated when power transfer is taking place from input to output. It also controls two secondary switches which act as synchronous rectifier switches during positive power flow. These switches are pulse-width-modulated when the power is being delivered back to the source.

The UCC3750 has an onboard sine wave reference with programmable frequencies of 20Hz, 25Hz and 50Hz. The reference is derived from a high-frequency (32kHz) crystal connected externally. Two frequency-select pins control an internal divider to give a sinusoidal output at 20Hz, 25Hz or 50Hz. The ring generator can also be used at other frequencies by sup-plying externally generated sine-waves to the chip or by clocking the crystal input at a fixed multiple of the desired frequency.

Other features included in the UCC3750 are programmable DC current limit (with buffer amplifier), a charge-pump circuit for gate drive voltage, internal 3V and 7.5V references, a triangular clock oscillator and a buffer amplifier for adding programmable DC offset to the output voltage. The UCC3750 also provides an uncommitted amplifier (AMP) for other signal processing requirements.

• Provides Control for Flyback Based Four Quadrant Amplifier Topology
• Onboard Sine Wave Reference with Low THD
• Selectable Ringing Frequency for Different Phone Systems (20Hz, 25Hz and 50Hz)
• Programmable Output Amplitude and DC Offset
• DC Current Limiting for Short Circuit Protection
• Secondary Side Voltage Mode Control
• Operates from a Single 5V Supply