UCC1800/1/2/3/4/5
UCC2800/1/2/3/4/5
UCC3800/1/2/3/4/5

MARCH 1999 - REVISED SEPTEMBER 2000 - SLUS270A

FEATURES

100

A Typical Starting Supply Current

500

A Typical Operating Supply

Current

Operation to 1MHz

Internal Soft Start

Internal Fault Soft Start

Internal Leading-Edge Blanking of the
Current Sense Signal

1 Amp Totem-Pole Output

70ns Typical Response from
Current-Sense to Gate Drive Output

1.5% Tolerance Voltage Reference

Same Pinout as UC3842 and
UC3842A

DESCRIPTION

The UCC1800/1/2/3/4/5 family of high-speed, low-power integrated cir-
cuits contain all of the control and drive components required for off-line
and DC-to-DC fixed frequency current-mode switching power supplies
with minimal parts count.

These devices have the same pin configuration as the UC1842/3/4/5
family, and also offer the added features of internal full-cycle soft start
and internal leading-edge blanking of the current-sense input.

The UCC1800/1/2/3/4/5 family offers a variety of package options, tem-
perature range options, choice of maximum duty cycle, and choice of crit-
ical voltage levels. Lower reference parts such as the UCC1803 and
UCC1805 fit best into battery operated systems, while the higher refer-
ence and the higher UVLO hysteresis of the UCC1802 and UCC1804
make these ideal choices for use in off-line power supplies.

The UCC180x series is specified for operation from 55

C to +125

the UCC280x series is specified for operation from 40

C to +85

C, and

the UCC380x series is specified for operation from 0

C to +70

Low-Power BiCMOS Current-Mode PWM

Part Number

Maximum Duty Cycle

Reference Voltage

Turn-On Threshold

Turn-Off Threshold

UCCx800

100%

7.2V

6.9V

UCCx801

50%

9.4V

7.4V

UCCx802

100%

12.5V

8.3V

UCCx803

100%

4.1V

3.6V

UCCx804

50%

12.5V

8.3V

UCCx805

50%

4.1V

3.6V

application

INFO

available

BLOCK DIAGRAM

UDG92009-3

UCC1800/1/2/3/4/5
UCC2800/1/2/3/4/5
UCC3800/1/2/3/4/5

DIL-8, SOIC-8 (Top View)
J or N, D Package

ELECTRICAL CHARACTERISTICS

Unless otherwise stated, these specifications apply for 55

+125°C for

UCC180x; 40°C

+85°C for UCC280x; 0°C

+70°C for UCC380x; V

=10V (Note 3); RT=100k from REF to RC;

CT=330pF from RC to GND; 0.1 F capacitor from V

to GND; 0.1 F capacitor from V

REF

to GND. T

PARAMETER

TEST CONDITIONS

UCC180X
UCC280X

UCC380X

UNITS

MIN

TYP

MAX

MIN

TYP

MAX

Reference Section

Output Voltage

=+25°C, I=0.2mA, UCCx800/1/2/4

4.925

5.00

5.075 4.925

5.00

5.075

=+25°C, I=0.2mA, UCCx803/5

3.94

4.00

4.06

3.94

4.00

4.06

Load Regulation

0.2mA<I<5mA

Line Regulation

=+25

=10V to Clamp (I

VCC

=25mA)

1.9

mV/V

=55°C to +125°C,

=10V to Clamp (I

VCC

=25mA)

2.5

2.1

mV/V

Total Variation

UCCx800/1/2/4 (Note 7)

4.88

5.00

5.10

4.88

5.00

5.10

UCCx803/5 (Note 7)

3.90

4.00

4.08

3.90

4.00

4.08

Output Noise Voltage

10Hz

10kHz, T

=+25°C (Note 9)

130

Long Term Stability

=+125°C, 1000 Hours (Note 9)

Output Short Circuit

OUT

VCC

REF

GND

COMP

ABSOLUTE MAXIMUM RATINGS (Note 1)

Voltage (Note 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.0V

Current (Note 2) . . . . . . . . . . . . . . . . . . . . . . . . . . 30.0mA

OUT Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.0A

OUT Energy (Capacitive Load) . . . . . . . . . . . . . . . . . . . 20.0

Analog Inputs (FB, CS) . . . . . . . . . . . . . . . . . . . . 0.3V to 6.3V
Power Dissipation at T

< +25°C (N or J Package) . . . . . 1.0W

Power Dissipation at T

< +25°C (D Package). . . . . . . . 0.65W

Storage Temperature Range . . . . . . . . . . . . .

65°C to +150°C

Lead Temperature (Soldering, 10 Seconds) . . . . . . . . +300°C

Note 1: Values beyond which damage may occur. All voltages

are with respect to GND. All currents are positive into
the specified terminal. Consult Unitrode databook for
information regarding thermal specifications and limita-
tions of packages.

Note 2: In normal operation V

is powered through a current

limiting resistor. Absolute maximum of 12V applies
when V

is driven from a low impedance source such

that I

does not exceed 30mA (which includes gate

drive current requirement).

COMP

REF

VCC

OUT

GND

CONNECTION DIAGRAMS

TSSOP-8 (Top View)
PW Package

UCC

PRODUCT OPTION

PACKAGE

TEMPERATURE RANGE

ORDERING INFORMATION

Temperature Range

Available Packages

UCC180X

55°C to +125°C

UCC280X

40°C to +85°C

N, D, PW

UCC380X

0°C to +70°C

N, D, PW

TEMPERATURE AND PACKAGE SELECTION

UCC1800/1/2/3/4/5
UCC2800/1/2/3/4/5
UCC3800/1/2/3/4/5

ELECTRICAL CHARACTERISTICS

Unless otherwise stated, these specifications apply for 55

+125°C for

UCC180x; 40°C

+85°C for UCC280x; 0°C

+70°C for UCC380x; V

=10V (Note 3); RT=100k from REF to RC;

CT=330pF from RC to GND; 0.1 F capacitor from V

to GND; 0.1 F capacitor from V

REF

to GND. T

PARAMETER

TEST CONDITIONS

UCC180X
UCC280X

UCC380X

UNITS

Oscillator Section

Oscillator Frequency

UCCx800/1/2/4 (Note 4)

kHz

UCCx803/5 (Note 4)

kHz

Temperature Stability

(Note 9)

2.5

Amplitude peak-to-peak

2.25

2.40

2.55

2.25

2.40

2.55

Oscillator Peak Voltage

2.45

Error Amplifier Section

Input Voltage

COMP=2.5V; UCCx800/1/2/4

2.44

2.50

2.56

2.44

2.50

2.56

COMP=2.0V; UCCx803/5

1.95

2.0

2.05

1.95

2.0

2.05

Input Bias Current

Open Loop Voltage Gain

COMP Sink Current

FB=2.7V, COMP=1.1V

0.3

3.5

0.4

2.5

COMP Source Current

FB=1.8V, COMP=REF1.2V

0.2

0.5

0.8

0.2

0.5

0.8

Gain Bandwidth Product

(Note 9)

MHz

PWM Section

Maximum Duty Cycle

UCCx800/2/3

100

UCCx801/4/5

Minimum Duty Cycle

COMP=0V

Current Sense Section

Gain

(Note 5)

1.10

1.65

1.80

1.10

1.65

1.80

V/V

Maximum Input Signal

COMP=5V (Note 6)

0.9

1.0

1.1

0.9

1.0

1.1

Input Bias Current

200

CS Blank Time

100

150

100

150

Over-Current Threshold

1.42

1.55

1.68

1.42

1.55

1.68

COMP to CS Offset

CS=0V

0.45

0.90

1.35

0.45

0.90

1.35

Output Section

OUT Low Level

I=20mA, all parts

0.1

0.4

0.1

0.4

I=200mA, all parts

0.35

0.90

0.35

0.90

I=50mA, VCC=5V, UCCx803/5

0.15

0.40

0.15

0.40

I=20mA, VCC=0V, all parts

0.7

1.2

0.7

1.2

OUT High V

SAT

-OUT)

I=20mA, all parts

0.15

0.40

0.15

0.40

I=200mA, all parts

1.0

1.9

1.0

1.9

I=50mA,VCC=5V, UCCx803/5

0.4

0.9

0.4

0.9

Rise Time

=1nF

Fall Time

=1nF

Undervoltage Lockout Section

Start Threshold (Note 8)

UCCx800

6.6

7.2

7.8

6.6

7.2

7.8

UCCx801

8.6

9.4

10.2

8.6

9.4

10.2

UCCx802/4

11.5

12.5

13.5

11.5

12.5

13.5

UCCx803/5

3.7

4.1

4.5

3.7

4.1

4.5

Stop Threshold (Note 8)

UCCx1800

6.3

6.9

7.5

6.3

6.9

7.5

UCCx1801

6.8

7.4

8.0

6.8

7.4

8.0

UCCx802/4

7.6

8.3

9.0

7.6

8.3

9.0

UCCx803/5

3.2

3.6

4.0

3.2

3.6

4.0

UCC1800/1/2/3/4/5
UCC2800/1/2/3/4/5
UCC3800/1/2/3/4/5

ELECTRICAL CHARACTERISTICS

Unless otherwise stated, these specifications apply for 55

+125°C for

UCC180x; 40°C

+85°C for UCC280x; 0°C

+70°C for UCC380x; V

=10V (Note 3); RT=100k from REF to RC;

CT=330pF from RC to GND; 0.1 F capacitor from V

to GND; 0.1 F capacitor from V

REF

to GND. T

PARAMETER

TEST CONDITIONS

UCC180X
UCC280X

UCC380X

UNITS

Undervoltage Lockout Section (cont.)

Start to Stop Hysteresis

UCCx800

0.12

0.3

0.48

0.12

0.3

0.48

UCCx801

1.6

2.4

1.6

2.4

UCCx802/4

3.5

4.2

5.1

3.5

4.2

5.1

UCCx803/5

0.2

0.5

0.8

0.2

0.5

0.8

Soft Start Section

COMP Rise Time

FB=1.8V, Rise from 0.5V to REF1V

Overall Section

Start-up Current

< Start Threshold

0.1

0.2

0.1

0.2

Operating Supply Current

FB=0V, CS=0V

0.5

1.0

0.5

1.0

VCC Internal Zener Voltage

=10mA (Note 8), (Note 10)

13.5

VCC Internal Zener Voltage Minus
Start Threshold Voltage

UCCx802/4 (Note 8)

0.5

1.0

0.5

1.0

Note 3: Adjust VCC above the start threshold before setting at 10V.
Note 4: Oscillator frequency for the UCCx800, UCCx802 and UCCx803 is the output frequency.

Oscillator frequency for the UCCx801, UCCx804 and UCCx805 is twice the output frequency.

Note 5: Gain is defined by:

COMP

0 8

Note 6: Parameter measured at trip point of latch with Pin 2 at 0V.
Note 7: Total Variation includes temperature stability and load regulation.
Note 8: Start Threshold, Stop Threshold and Zener Shunt Thresholds track one another.
Note 9: Guaranteed by design. Not 100% tested in production.
Note 10: The device is fully operating in clamp mode as the forcing current is higher than the normal operating supply current.

PIN DESCRIPTIONS

COMP: COMP is the output of the error amplifier and the
input of the PWM comparator.

Unlike other devices, the error amplifier in the UCC3800
family is a true, low output-impedance, 2MHz operational
amplifier. As such, the COMP terminal can both source
and sink current. However, the error amplifier is internally
current limited, so that you can command zero duty cycle
by externally forcing COMP to GND.

The UCC3800 family features built-in full cycle Soft Start.
Soft Start is implemented as a clamp on the maximum
COMP voltage.

CS: CS is the input to the current sense comparators.
The UCC3800 family has two different current sense
comparators: the PWM comparator and an over-current
comparator.

The UCC3800 family contains digital current sense filter-
ing, which disconnects the CS terminal from the current
sense comparator during the 100ns interval immediately
following the rising edge of the OUT pin. This digital filter-
ing, also called leading-edge blanking, means that in

most applications, no analog filtering (RC filter) is
required on CS. Compared to an external RC filter tech-
nique, the leading-edge blanking provides a smaller ef-
fective CS to OUT propagation delay. Note, however,
that the minimum non-zero On-Time of the OUT signal is
directly affected by the leading-edge-blanking and the
CS to OUT propagation delay.

The over-current comparator is only intended for fault
sensing, and exceeding the over-current threshold will
cause a soft start cycle.

FB: FB is the inverting input of the error amplifier. For
best stability, keep FB lead length as short as possible
and FB stray capacitance as small as possible.

GND: GND is reference ground and power ground for all
functions on this part.

OUT: OUT is the output of a high-current power driver
capable of driving the gate of a power MOSFET with
peak currents exceeding

750mA. OUT is actively held

low when V

is below the UVLO threshold.

UCC1800/1/2/3/4/5
UCC2800/1/2/3/4/5
UCC3800/1/2/3/4/5

The high-current power driver consists of FET output de-
vices, which can switch all of the way to GND and all of
the way to V

. The output stage also provides a very

low impedance to overshoot and undershoot. This means
that in many cases, external schottky clamp diodes are
not required.

RC: RC is the oscillator timing pin. For fixed frequency
operation, set timing capacitor charging current by con-
necting a resistor from REF to RC. Set frequency by con-
necting a timing capacitor from RC to GND. For best
performance, keep the timing capacitor lead to GND as
short and direct as possible. If possible, use separate
ground traces for the timing capacitor and all other func-
tions.

The frequency of oscillation can be estimated with the
following equations:

UCCx800/1/2/4:

R C

1 5

UCCx803, UCCx805:

R C

where frequency is in Hz, resistance is in ohms, and ca-
pacitance is in farads. The recommended range of timing
resistors is between 10k and 200k and timing capacitor is
100pF to 1000pF. Never use a timing resistor less than
10k.

To prevent noise problems, bypass VCC to GND with a
ceramic capacitor as close to the VCC pin as possible.

An electrolytic capacitor may also be used in addition to
the ceramic capacitor.

REF: REF is the voltage reference for the error amplifier
and also for many other functions on the IC. REF is also
used as the logic power supply for high speed switching
logic on the IC.

When V

is greater than 1V and less than the UVLO

threshold, REF is pulled to ground through a 5k ohm re-
sistor. This means that REF can be used as a logic out-
put indicating power system status. It is important for
reference stability that REF is bypassed to GND with a
ceramic capacitor as close to the pin as possible. An
electrolytic capacitor may also be used in addition to the
ceramic capacitor. A minimum of 0.1

F ceramic is re-

quired. Additional REF bypassing is required for external
loads greater than 2.5mA on the reference.

To prevent noise problems with high speed switching
transients, bypass REF to ground with a ceramic capaci-
tor very close to the IC package.

VCC: V

is the power input connection for this device.

In normal operation V

is powered through a current

limiting resistor. Although quiescent V

current is very

low, total supply current will be higher, depending on
OUT current. Total V

current is the sum of quiescent

current and the average OUT current. Knowing the

operating frequency and the MOSFET gate charge (Qg),
average OUT current can be calculated from:

OUT

PIN DESCRIPTIONS (cont.)

Figure 1. Oscillator.

Figure 2. Error amplifier gain/phase response.

The UCC3800/1/2/3/4/5 oscillator generates a sawtooth
waveform on RC. The rise time is set by the time constant of
R

and C

. The fall time is set by CT and an internal transis-

tor on-resistance of approximately 125 . During the fall
time, the output is off and the maximum duty cycle is re-
duced below 50% or 100% depending on the part number.
Larger timing capacitors increase the discharge time and re-
duce the maximum duty cycle and frequency.

UCC1800/1/2/3/4/5
UCC2800/1/2/3/4/5
UCC3800/1/2/3/4/5

1000

100

1000

Oscillator Freq.

(kHz)

R (k )

100pF

200pF

330pF

1nF

Figure 5. UCC1803/5 oscillator frequency vs. R

and

95.5

96.5

97.5

98.5

99.5

100

1000

Oscillator Frequency (kHz)

Maxim

um Duty Cyc

le (%)

100pF

200pF

330pF

Figure 6. UCC1800/2/3 maximum duty cycle vs.
oscillator frequency.

1000

100

1000

Oscillator Freq.

(kHz)

R (k )

100pF

200pF

330pF

1nF

Figure 4. UCC1800/1/2/4 oscillator frequency vs. R

and C

4.00

3.98

3.96

3.94

3.92

3.90

3.88

3.86

3.84

3.82

4.2

4.4

4.6

4.8

5.2

5.4

5.6

5.8

(V)

REF

Figure 3. UCC1803/5 V

REF

vs. V

; I

LOAD

= 0.5mA.

46.5

47.5

48.5

49.5

100

1000

Oscillator Frequency (kHz)

Maxim

um Duty Cyc

le (%)

100pF

200pF

330pF

Figure 7. UCC1801/4/5 maximum duty cycle vs.
oscillator frequency.

100

200

300

400

500

600

700

800

900 1000

Oscillator Frequency (kHz)

(
mA)

= 10V

, 1nF

V = 8V

, 1nF

V = 10V

, No Load

= 8V, No Load

Figure 8. UCC1800 I

vs. oscillator frequency.

UCC1800/1/2/3/4/5
UCC2800/1/2/3/4/5
UCC3800/1/2/3/4/5

100

150

200

250

300

350

400

450

500

100

200

300

400

500

600

700

800

900

1000

(pF)

Dead Tim

e (ns)

UCC1803/5

UCC1800/1/2/4

Figure 9. Dead time vs. C

, R

= 100k.

0.6

0.7

0.8

0.9

1.0

1.1

-55-50

-25

100

125

Temperature (°C)

COMP to CS Offset (V

olts)

Slope = 1.8mV/ C

Figure 10. COMP to CS offset vs. temperature,
CS = 0V.

100

200

300

400

500

600

700

800

900 1000

Oscillator Frequency (kHz)

(
mA)

= 10V

, 1nF

V = 8V

, 1nF

V = 10V

, No Load

= 8V, No Load

Figure 8. UCC1805 I

vs. oscillator frequency.

UNITRODE CORPORATION
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2001, Texas Instruments Incorporated

IMPORTANT NOTICE

Customers are responsible for their applications using TI components.

In order to minimize risks associated with the customer's applications, adequate design and operating
safeguards must be provided by the customer to minimize inherent or procedural hazards.

Resale of TI's products or services with

statements different from or beyond the parameters stated by TI for

Also see: Standard Terms and Conditions of Sale for Semiconductor Products. www.ti.com/sc/docs/stdterms.htm

Mailing Address:

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Post Office Box 655303
Dallas, Texas 75265

2001, Texas Instruments Incorporated

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