UCC3752N [TI]

Resonant Ring Generator Controller;


型号：	UCC3752N
厂家：	TEXAS INSTRUMENTS
描述：	Resonant Ring Generator Controller 电信信息通信管理光电二极管电信集成电路
文件：	总6页 (文件大小：75K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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

SENSE

DC SIGNAL

AC SIGNAL

12V

SAMPLING

CIRCUIT

OUT

12V

N:1

BYP1

BYP2

VS12

DRVS

N/C

OHD

VDD

11 DRV1

ENABLE 10

DCLIM

UCC3752

OFFHOOK

13 DRV2

GND

XTAL2 15

XTAL1

PGND

FS0

FS1

3.579545MHz

UDG-98058

SLUS269 - JULY 1999

UCC2752

UCC3752

CONNECTION DIAGRAMS

ABSOLUTE MAXIMUM RATINGS

Input Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2V

Analog Inputs (OHD, DCLIM, XTAL1, XTAL2)

Maximum Forced Voltage. . . . . . . . . . . . . . . . . . . . –0.3 to 5V

Logic Inputs

(TOP VIEW) DIL-16, SOIC-16

N or D Packages

Maximum Forced Voltage . . . . . . . . . . . . . . . . . . –0.3 to 7.5V

Reference Output Current (VDD). . . . . . . . . . . Internally Limited

Output Current (DRV1, DRV2, DRVS) Pulsed . . . . . . . . . . 1.5A

Operating Junction Temperature . . . . . . . . . . –40°C to +125°C

Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C

OFFHOOK

N/C

16 XTAL1

15 XTAL2

14 PGND

13 DRV2

12 DRVS

11 DRV1

GND

Note: Unless otherwise indicated, voltages are referenced to

ground and currents are positive into, negative out of, the spe-

cific terminals. Pulsed is defined as a less than 10% duty cycle

with a maximum duration of 500 S.

VDD

DCLIM

OHD

Table I. Frequency selectability decoding.

FS0

10 ENABLE

VS12

FS1

FS0

MODE

Sine Wave

Frequency (Hz)

FS1

FS0

FDRVS

FDRV – FDRVS

89.469kHz

89.464kHz

89.439kHz

20Hz

25Hz

50Hz

ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications hold for TA = 0°C to 70°C for the

UCC3752 and –40°C to +85°C for the UCC2752, TA = TJ.

PARAMETER

V12 Supply Current Section

Supply Current

TEST CONDITIONS

MIN

TYP

MAX UNITS

ENABLE = 0V

ENABLE = 5V

0.5

Internal Reference with External Bypass Section

Output Voltage (VDD)

4.85

5.15

Load Regulation

Line Regulation

0mA ≤IVDD ≤2mA

10V < VS12 < 13V, IVDD = 1mA

VDD = 0

Short Circuit Current

Output Drivers Section (DRV1, DRV2)

Pull Up Resistance

Pull Down Resistance

Rise Time

I_LOAD= 10mA to 20mA

C_LOAD= 1nF

100

Fall Time

C_LOAD= 1nF

Output Drivers Section (DRVS)

Pull Up Resistance

Pull Down Resistance

Sample Pulse-Width

Rise Time

_LOAD= 10mA to 20mA

I_LOAD= 10mA to 20mA

Mode 1 (Table 1)

C_LOAD= 1nF

280

100

Fall Time

C_LOAD= 1nF

UCC2752

UCC3752

ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications hold for TA = 0°C to 70°C for the

UCC3752 and –40°C to +85°C for the UCC2752, TA = TJ.

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX UNITS

Current Limit Section

DCLIM Threshold

300

DCLIM Input Current

OffHook Detect Section

OHD Threshold

VDCLIM = 0V

VOHD = 0V

–100

300

–100

4.0

OHD Input Current

Offhook VOH

IOFFHOOK = 1mA

Offhook VOL

IOFFHOOK = –1mA

I_LOAD= 0mA to 1mA

1.0

Offhook Pull-Up Impedance

Offhook Pull-Down Impedance

400

250

Frequency Section (Table 1)

Primary Switching Frequency

Sampling Switching Frequency

All cases 3.579545 MHz Crystal

FS0 = 0, FS1 = 0, Mode 1, (Table 1)

FS0 = 1, FS1 = 0, Mode 1

89489

89469

89464

89439

FS0 = 0, FS1 = 1, Mode 1

PIN DESCRIPTIONS

DCLIM: Primary current sense input. Signal proportional GND: Reference point for all the internal voltages and

to the primary switch current. All outputs are turned off common return for the device.

when a threshold of 300mV is exceeded on this pin. This

current-limit works on a cycle-by-cycle basis.

OFFHOOK: Output indicating the off-hook condition. This

signal can be used by an external circuit to switch to a

DRV1, DRV2: Low impedance driver outputs for the pri- line from the ring generator output to the DC voltage.

mary switches. DRV1 and DRV2 are complimentary and

have 50% duty cycle.

OHD: Off-Hook Detect. Voltage proportional to output cur-

rent DC level is fed into this pin and compared to an inter-

DRVS: Low impedance driver output for the sampling nal threshold of 300mV. If the threshold is exceeded, the

switch(es). The pulse width of this output is 280ns. OFFHOOK output goes high.

Typically, a pulse transformer is used to couple the short

sampling pulses at DRVS to the floating sampling

switch(es).

PGND: Return point for the output drivers. Connect to

GND at a single point in the circuit.

VDD: Internal regulated 5V supply. This voltage is used to

power all the internal precision circuits of the IC. This pin

needs to be bypassed to GND with ceramic capacitor.

ENABLE: Logic input which turns off the outputs when

low.

FS0, FS1: Frequency select pins for determining the dif-

VS12: External 12V power supply for the IC. Powers VDD

ference frequency between primary and secondary

and provides voltage for the output drivers.

pulses under normal operation. These pins can be hard-

XTAL1, XTAL2: Pins for connecting precision Crystal to

attain the accurate output frequencies. An external

square-wave pulse can also be applied to XTAL2 if XTAL1

is tied to VDD/2.

wired to GND or VDD to get one of the available output

frequencies (20,25 and 50 Hz). See Table 1 in the spec

table.

UCC2752

UCC3752

BLOCK DIAGRAM

N/C

300mV

11 DRV1

13 DRV2

12 DRVS

14 PGND

1-SHOT

DCLIM

ENABLE 10

XTAL1 16

MODULO

COUNTER

MODULO

COUNTER

XTAL2 15

OHD

ONE-SHOT

1/FOSC

300mV

MODULO

COUNTER

MODULO

1,800

COUNTER

2/FOSC

OFFHOOK

GND

VS12

VDD

MODULO

3,560

COUNTER

ONE-SHOT

5 VOLT

REFERENCE

FS1

FS0

MODULO

4,480

COUNTER

4.5V

UDG-98023

APPLICATION INFORMATION

Power Stage Operation

stress of Q1 and Q2. Transformer turns ratio is

determined by the output voltage requirements. On the

secondary side, the high frequency waveform is sampled

at a predetermined frequency (e.g. 89.469 kHz) which dif-

fers from the primary switching frequency by the desired

output frequency (e.g. 20 Hz). The sampling is accom-

plished using a bi-directional switching circuit as shown in

Figure 1 and Figure 2. Figure 1 shows the sampling

mechanism consisting of two back-to-back FET switches

allowing current flow in both directions. The sampling can

also be done with a single active switch and a full-bridge

rectifier as shown in Fig. 2. The DRVS pin of the

UCC3752 provides the drive signal for the sampling

switch(es) and this signal is coupled through a pulse

transformer. Typical pulsewidth of the sampling signal is

280nS. As a result of sampling, the resultant output sig-

nal matches the secondary voltage in amplitude and has

a low output frequency desired for ring generation.

The power stage used for the UCC3752 application has

two distinct switching circuits which together produce the

required low frequency signal on the output. The primary

side switching circuit consists of a current fed push-pull

resonant circuit that generates the high frequency sinu-

soidal waveform across the transformer winding. The op-

eration of this type of circuit is extensively covered in

Unitrode Application notes U-141 and U-148. Resonant

components C_R1, C_R2, L_R, N should be chosen so that

the primary and secondary resonances are well

matched. Also, for the UCC3752 operation, switching fre-

quency is fixed by crystal selection. So, the resonant

components must be selected to yield a resonant fre-

quency close enough to the switching frequency to get a

low distortion sine-wave. Practically, since it is impossi-

ble to get an exact match between the two frequencies,

the switching frequency should always be higher than

the resonant frequency to ensure low distortion and take

advantage of ZVT operation. Switches Q1 and Q2 are

pulsed at 50% duty cycle at the switching frequency

(89.489 kHz) determined by a crystal (3.579545 MHz)

connected to the UCC3752. The input voltage for the

resonant stage (typically 12V) determines the voltage

The secondary winding of the power transformer also has

a tap (or a separate winding) to generate a loosely regu-

lated DC voltage. This DC voltage can be used to offset

the ring generator output. It an also be used as a power

supply for supplying talk battery voltage in some applica-

tions.

UCC2752

UCC3752

APPLICATION INFORMATION (cont.)

TO TRANSFORMER

DRVS

TO OUTPUT

Figure 1. Sampling circuit with two FETs.

Figure 2. Sampling circuit with single FET and

full-bridge rectifier.

UNITRODE CORPORATION

7 CONTINENTAL BLVD. • MERRIMACK, NH 03054

TEL. (603) 424-2410 • FAX (603) 424-3460

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UCC3752N [TI]

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