FEATURES

• 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

DESCRIPTION

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 supplying 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.