UCC2750

UCC3750

PRELIMINARY

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

fre-

quency-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 fre-

quencies 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, in-

ternal 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.

Source Ringer Controller

15

28

2

4

26

27

25

6

5

7

18

16

17

10

OUT2

NEG2

VS2

VDD

VS1

VCP

OUT1

NEG1

REF

ENBL

GD3

GD2

5V

SINFLT

24

23

1

11

12

OUTDC

NEGDC

RT

RGOOD

CT

GD1

AMPOUT

XTAL1

XTAL2

13

14

22

21

AMPIN

FS0

FS1

20

19

V

IN

48V

UCC3750

9

8

3

SINREF

SWRLY

GND

C17

0.047

µF

V

OUT

0V

–48V

V

OUT

TYPICAL APPLICATION

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

SLUS172A - DECEMBER 1999

UDG-99073

application

INFO

available