鈥?/div>
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 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.
TYPICAL APPLICATION
0V
V
OUT
鈥?8V
V
IN
48V
V
OUT
28
GD2
26
27
25
REF
VCP
GD3 ENBL
2
24
23
1
11
12
13
14
22
21
20
19
GD1
UCC3750
4
6
5
7
5V
RT
CT
RGOOD
OUTDC
NEGDC
AMPOUT
AMPIN
VS2
VS1
VDD
OUT2
15
NEG2
OUT1
18
16
XTAL1
XTAL2
FS0
FS1
SINREF
9
C17
0.047碌F
NEG1
SINFLT
SWRLY
8
GND
3
17
10
UDG-99073
SLUS172A - DECEMBER 1999