UCC2752
UCC3752
PRELIMINARY
Resonant Ring Generator Controller
FEATURES
DESCRIPTION
• Novel Topology for Low-Cost, Efficient The UCC3752 controller is designed for driving a power stage that gener-
Generation of Ring Voltage
ates low frequency, high voltage sinusoidal signals for telephone ringing
applications. The controller and the power stage are most suitable for up to
5 line applications where low cost, high efficiency and minimum parts count
are critical. A semi-regulated DC voltage is added as an offset to the ring-
ing signal. The ring generator operation is non-isolated and open loop.
• Suitable for Multi-Line Operation
• Selectable 20, 25 and 50 Hz Ring
Frequency
• Secondary (AC) Current Limiting
Generates an Off-Hook Detect Signal
The UCC3752 directly drives primary side switches used to implement a
push-pull resonant converter topology and transformer coupled sampling
switches located on the secondary of the converter. For normal ring signal
generation, the primary switching frequency and secondary sampling fre-
quency are precisely offset from each other by the ringing frequency to pro-
duce a high voltage low frequency alias signal at the output. The off-hook
condition is detected by sensing the AC current and when AC limit is ex-
ceeded, a flag is generated on the OFFHOOK pin.
• Primary Current Limiting to Turn
Power Stage Off Under Fault
Conditions
• Operates from a Single 12V Supply
The drive signal frequencies are derived from a high frequency (3579545
Hz) crystal. The primary switching frequency is 89.489 kHz and the sam-
pling frequency is 20, 25 or 50 Hz less depending on the status of fre-
quency select pins FS0 and FS1.
The circuits described in this datasheet are covered under US Patent #5,663,878 and other patents pending.
TYPICAL APPLICATION
D1
R
SENSE
L
IN
T1
DC SIGNAL
AC SIGNAL
C
DC
V
IN
V
V
1
12V
L
L
R
R
C
C
F
R2
SAMPLING
CIRCUIT
OUT
12V
N:1
C
BYP1
9
12
2
6
4
C
BYP2
VS12
DRVS
N/C
OHD
VDD
C
R1
Q1
11 DRV1
ENABLE 10
5
DCLIM
UCC3752
OFFHOOK
1
Q2
13 DRV2
GND
XTAL2 15
XTAL1
16
PGND
14
FS0
7
FS1
8
3
3.579545MHz
UDG-98058
SLUS269 - JULY 1999