UCC3889N - Texas Instruments - Datasheet.Directory

Off-line Power Supply Controller

•Trans form erless Off -line

Applications

•Ideal Primary-side Bias Supply

•Efficient BiCMOS Design

•Wide Input Range

•Fixed or Ad justable

Low Voltage Output

•Uses Low Cost SMD Inductors

•Short Circuit Prot ecte d

•Opt ional Isolation Capability

The UCC18 89 controller is optimized for use as an of f-line, low power, low voltage,

regulated bias supply. The unique circuit topology utilized in this device can be

visualized as two cascaded flyback converters, each operating in the discontinu-

ous mode, and both driven from a single external power switch. The significant

benefit of this approach i s the abili ty to achieve voltage conversion ratios of 400V

to 1 2V wit h no t ra nsf or m er an d low int er nal los ses .

The control algorithm utilized by the UCC1889 is to force the switch on time to be

inversely proportional to the input line voltage while the switch off time is made in-

versely proportiona l to the out put volt age . This act io n is autom at ica lly cont r olled by

an internal feedback loop and referenc e. The casc aded con figura tio n allow s a volt-

age conversion from 400V to 12V to be achieved with a switch dut y cycle greater

than 10%. This topology also offers inherent short circuit protection since as the

o ut put volta g e fa lls to zer o, th e swit c h of f time appr oac hes infin ity.

The output voltage can be easily set to 12V or 18V. Moreover, it can be pro-

grammed for other output voltages less than 18V with a few additional compo-

nents. An isolated version can be achieved with this topology as described further

in Unit rode Applicatio n N o te U-14 9 .

UCC1889

UCC2889

UCC3889

SLUS158A - FEBRUARY 1995 - REVISED FEBRUARY 2003

FEATURES DESCRIPTION

OPERATION

With referenc e t o the application d iagram below, when input volt a g e is fir st a pplied ,

the R ON current into TON is direc ted t o V CC where it charges the externa l capacito r ,

C3, connected to VCC. As voltage builds on VCC, an internal undervoltage lockout

holds the circuit off and the output at DRIVE low until VCC reaches 8.4V. At this

time, DRIVE goes high turning on the power switch, Q1 , and redir ecting the cur rent

into TON to the timing capacitor, CT. CT charges to a fixed threshold with a current

ICHG=0.8 • (VIN - 4.5V)/RON. Since DRIVE will only be high for as long as CT

charges, the power switch on time will be inversely proportional to line voltage.

This provides a const ant line v olt age- switc h on tim e produc t.

No te : This d evice inco rpo rates patent ed t ech nology used un der license from Lambd a E lect ron ics, Inc .

T YPICAL APP LI CATIO N

UDG-93060-1

UCC1889

UCC2889

UCC3889

OPE RATI ON (cont.)

At the end of the on time, Q1 is turn ed off and the RON

current into TON is again diverted to VCC. Thus the cur-

rent through RON, which charges CT during the on time,

contribut es to supplying control power during the of f time.

The power switch off time is controlled by the di scharge

of CT which, in turn, is programmed by the regulated out-

put voltage. The relationship between CT discharge cur-

rent, IDCHG, and output voltage is illustrated as fo llows :

1. When VOUT = 0, the off time is infinite. This feature

provides inherent short circuit protection. However, to

ensure output voltage startup when the output is not a

short, a high value resistor, RS, is placed in parallel

with CT to establish a minimum switching frequency.

2. As VOUT rises above approximately 0.7V to its regu-

lated val ue, IDCHG is defined by ROFF, and therefore is

equal to:

IDCHG = (V OUT - 0.7V) / ROFF

As VOUT increases, IDCHG increases resulting in the

reduction of off time. The frequency of operation in-

creases and VOUT rises quickly to its regulated value.

3. In this region, a transconductance amplifier reduces

IDCHG in order to maintain V OUT in regulation.

4. If VOUT should rise above its regulation range, IDCHG

falls to zero and the circui t returns to the minimum fre-

quency established by RS and CT.

The range of switching frequencies is established by

RON, ROFF, RS, and CT as follows:

Frequency = 1/(TON + TOFF)

TON = RON • CT • 4.6 V/(VIN - 4.5V)

TOFF (max) = 1.4 • RS • CT

Regions 1 and 4

TOFF = ROFF • CT • 3.7V /(VOUT - 0.7V)

Region 2, excluding the effects of R S

which have a minimal impact on TOFF.

The above equations assume that VCC equals 9V. The

voltage at TON increases from approximately 2.5V to

6.5V while CT is chargin g. To take this into account, VIN

is adjusted by 4.5V in the calculation of TON. The voltage

at TOFF is approximately 0.7V.

DESI GN EXAMPLE

The UCC3889 regulates a 12 volt, 1 Watt nonisolated DC output from AC inputs between 80 and 265 volts. In this ex-

ample , the IC i s pro grammed to deliver a maximum on time gate drive pulse width of 2.4 microseconds which occurs

at 80 VAC. The corresponding switching frequency is approximatel y 100kHz at low line, and overall efficiency is ap-

proximat e ly 50%. Additional design informat ion is ava ilable in Unitrode Applicat ion Note U-149.

UDG-93062-3

PARAMETER TEST CO NDIT IONS MIN TYP MAX UNITS

Gene ral

VCC Zene r Voltage ICC < 1. 5m A 8. 6 9. 0 9. 3 V

Startup Current VOUT = 0 1 5 0 2 5 0 µA

Oper at ing Cur ren t I(VOUT) VOUT = 11V, F = 15 0kHz 1.2 2.5 mA

Under-Voltage-Lockout

Start Threshol d VOUT = 0 8.0 8.4 8.8 V

Min imum O per ating Volt age af t er Star t V OUT = 0 6.0 6.3 6.6 V

Hysteresis VOUT = 0 1. 8 V

Oscillator

Amplitude VCC = 9V 3 .5 3.7 3.9 V

CT to DRIVE high Propa gation Delay Overdrive = 0.2V 10 0 200 ns

CT to DRIVE low Propaga tion De lay Over drive = 0.2 V 50 1 00 ns

Driver

VO L I = 20mA, V CC = 9V 0 .1 5 0. 4 V

I = 100mA, VCC = 9 V 0. 7 1. 8 V

VO H I = −20mA, VCC = 9V 8. 5 8. 8 V

I = −100mA, V CC = 9V 6 .1 7.8 V

Rise Time CLOAD = 1nF 35 70 ns

Fall Time CLOAD = 1nF 30 60 ns

Line Vol t age Det ect i on

Charge C oe fficient : I CHG / I(TON) VCT = 3V, DRIVE = High, I(T ON) = 1m A 0 .7 3 0 .7 9 0 .8 5

Minimum Line Voltage for Fault RON = 330k 60 80 100 V

Minimum Current I(TON) for Fault RON = 330 k 220 µA

On Time During Fault C T = 150pF, VLINE = M in − 1V 2 µs

Oscillat or Restart Delay aft er Fault 0.5 ms

VOUT Error Amp

VOUT Regulat ed 12 V (ADJ Open ) VCC = 9V, IDCHG = I(TOFF)/2 11.2 11.9 12.8 V

VOUT Re gulat ed 18 V (ADJ = 0V) V CC = 9V, IDCHG = I(TOFF)/2 16.5 17.5 19.5 V

Discharge Ratio: IDCHG / I(TOFF)I(TOFF) = 50µA0.931.001.07

Voltage at TOFF I(TOFF) = 50µA 0.6 0.95 1.3 V

Regula tion gm (Note 1) Max IDCHG = 50µA 1.0 mA/V

Ma x IDCHG = 125µA 0.8 1.7 2.9 mA/V

Unless othe rwise stat ed , thes e specificat ions hold for TA = 0°C to 70°C for the

UCC3889, -40°C to +85°C for the UCC2889, and -55 °C to +125°C for the UCC1889.

No load at DRIVE pin (CLOAD=0).

ELECTRICAL CHARACTERISTICS

DIL- 8, SO IC-8 (Top View )

N or J, D Package

CONNECTI ON DIAGRAM

ICC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5mA

Current in to T ON Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5mA

Vo ltage on VOUT Pi n. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 0V

Current in to T OFF Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250µA

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

No te : Unless o th erwise ind icat ed, voltages are ref erenced to

g rou nd and c urrent s are pos itive int o, negative out of, the spe ci-

fied ter mina ls .

ABSOL UTE MAXIMUM RATINGS

UCC1889

UCC2889

UCC3889

No te 1: gm is defined as

∆IDCHG

∆VOUT

for the values of V

OUT

when V

OUT

is in regulat io n. The t wo point s used to c alculat e gm are for

DCHG

at 65% and 35% o f it s ma ximum va lue.

ADJ: The ADJ pin is used to provide a 12V or an 18V

regul ated supp ly witho ut additi onal ex ternal components.

To select the 12V option, ADJ pin is left open. To select

the 18V option, ADJ pin must be grounded. For other out-

put voltages less than 18V, a resistor divider between

VOUT, ADJ and GND is needed. Note, however, that for

output voltages less than VCC, the device needs addi-

tional bootstrapping to VCC from an external source such

as the line voltage. If so, precautions must be taken to

ensure that total ICC does not exceed 5mA.

CT (tim ing capacitor): The signal voltage across CT has

a peak-to-peak swi ng of 3.7V for 9V VCC. As the voltage

on CT crosses the oscillator upper threshold, DRIVE goes

low. As the voltage on CT crosses the oscillator lower

threshold, DRIVE goes high.

DRIVE: This output is a CMOS stage capable of sinking

200mA peak and sourcing 150mA peak. The output volt-

age swing is 0 to VCC.

GND (chip ground): All voltages are measured with re-

spect to G ND.

TOFF (regulated output control): TOFF sets the dis-

charge current of the timing capacitor through an external

resistor connected between VOUT and TOFF.

TON (line voltage control): TON serves three functions.

When CT is discharging (off time), the current through

TON is routed to VCC. Wh en CT is charg ing (on time), the

current through TON is split 80% to set the CT charge

time and 20% to sense minimum line voltage which oc-

curs for a TON current of 220µA. For a minimum l ine volt-

age of 80V, RON is 330kΩ.

The CT voltage slightly affects the value of the charge

current during the on time. During th is time, the v oltage at

the T ON p in increases from approxim ately 2.5V to 6.5V.

VCC (chip supply voltage): The supply voltage of the

device at pin VCC is internally clamped at 9V. Normally,

VCC is not directly powered from an external voltage

source such as the l ine vol tage. In the event that VCC is

directly connected to a voltage source for additional boot-

strapping, precauti ons mu st be taken to ensure that total

ICC does not exceed 5mA.

VOUT (regulated output): The VOUT pin is directly con-

nected to the power supply output voltage. When VOUT is

gr eater than V CC, VOUT bootstraps VCC.

UCC1889

UCC2889

UCC3889

PIN DES CRIPTIONS

BL OCK DIAG RAM

UDG-93064-2

UCC1889

UCC2889

UCC3889

T YPICAL WAVE FO RMS

UNITRODE INTEGRATED CIRCUITS

7 CONTINENTAL BLVD. • MERRIMACK, NH 03054

TEL. 603-424-2410 • FAX 603-424-3460

UCC1889

UCC2889

UCC3889

PACKAGE OPTION ADDENDUM

www.ti.com 17-Aug-2012

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status (1) Package Type Package

Drawing Pins Package Qty Eco Plan (2) Lead/

Ball Finish MSL Peak Temp (3) Samples

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UCC2889D ACTIVE SOIC D 8 75 Green (RoHS