UCC2813DTR-3 - Texas Instruments

UCC2813-0/-1/-2/-3/-4/-5

UCC3813-0/-1/-2/-3/-4/-5

04/99

FEATURES

100µA Typical Starting Supply Current

500µA 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 UCC3802, UC3842, and

UC3842A

DESCRIPTION

The UCC3813-0/-1/-2/-3/-4/-5 family of high-speed, low-power inte-

grated circuits 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 UC3842/3/4/5

family, and also offer the added features of internal full-cycle soft start

and internal leading-edge blanking of the current-sense input.

The UCC3813-0/-1/-2/-3/-4/-5 family offers a variety of package options,

temperature range options, choice of maximum duty cycle, and choice

of critical voltage levels. Lower reference parts such as the UCC3813-3

and UCC3813-5 fit best into battery operated systems, while the higher

reference and the higher UVLO hysteresis of the UCC3813-2 and

UCC3813-4 make these ideal choices for use in off-line power supplies.

The UCC2813-x series is specified for operation from –40°C to +85°C

and the UCC3813-x series is specified for operation from 0°C to +70°C.

BLOCK DIAGRAM

Low Power Economy BiCMOS Current Mode PWM

UDG-96134

Part Number Maximum Duty Cycle Reference Voltage Turn-On Threshold Turn-Off Threshold

UCCx813-0 100% 5V 7.2V 6.9V

UCCx813-1 50% 5V 9.4V 7.4V

UCCx813-2 100% 5V 12.5V 8.3V

UCCx813-3 100% 4V 4.1V 3.6V

UCCx813-4 50% 5V 12.5V 8.3V

UCCx813-5 50% 4V 4.1V 3.6V

ORDERING INFORMATION

UCC2813-0/-1/-2/-3/-4/-5

UCC3813-0/-1/-2/-3/-4/-5

DIL-8 or SOIC-8 (TOP VIEW)

N or D PACKAGE

OUT

VCC

REF

GND

COMP

CONNECTION DIAGRAMS

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

VCC Current. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.0mA

OUT Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0A

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

Analog Inputs (FB, CS) . . . . . . . . . . . . . . . . . . . . –0.3V to 6.3V

Power Dissipation at TA< +25°C (N Package). . . . . . . . . 1.0W

Power Dissipation at TA< +25°C (D Package). . . . . . . . 0.65W

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

Junction Temperature. . . . . . . . . . . . . . . . . . . –55 C to +150°C

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

ABSOLUTE MAXIMUM RATINGS (Note 1)

Note 1: All voltages are with respect to GND. All currents are

positive into the specified terminal. Consult Unitrode Integrated

Circuits databook for information regarding thermal specifica-

tions and limitations of packages.

Note 2: In normal operation VCC is powered through a current

limiting resistor. Absolute maximum of 12V applies when VCC

is driven from a low impedance source such that ICC does not

exceed 30mA.

COMP

REF

VCC

OUT

GND

TSSOP-8 (TOP VIEW)

PW PACKAGE

UCC

PACKAGE

813

TEMPERATURE RANGE

–

PRODUCT OPTION

ORDERING INFORMATION

TEMPERATURE RANGE PACKAGES

UCC2813 –40°C TO +85°C N, D, PW

UCC3813 0°C TO +70°C N, D, PW

ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for –40°C ≤TA≤+85°C for

UCC2813-x; 0°C ≤TA≤+70°C for UCC3813-x; VCC = 10V (Note 3); RT = 100k from REF to RC; CT=330pF from RC to GND;

0.1µF capacitor from VCC to GND; 0.1µF capacitor from VREF to GND. TA=T

PARAMETER TEST CONDITIONS UCC2813-x

UCC3813-x UNITS

MIN TYP MAX

Reference Section

Output Voltage TJ= +25°C, I = 0.2mA, UCCx813-0/-1/-2/-4 4.925 5.00 5.075 V

TJ= +25°C, I = 0.2mA, UCCx813-5 3.94 4.00 4.06 V

Load Regulation 0.2mA<I<5mA 10 30 mV

Total Variation UCCx813 -0-1/-2/-4 (Note 7) 4.84 5.00 5.10 V

UCCx813-5 (Note 7) 3.84 4.00 4.08 V

Output Noise Voltage 10Hz ≤f≤10kHz, TJ= +25°C (Note 9) 70 µV

Long Term Stability TA= +125 C, 1000 Hours (Note 9) 5 mV

Output Short Circuit –5 –35 mA

Oscillator Section

Oscillator Frequency UCCx813-0/-1/-2/-4 (Note 4) 40 46 52 kHz

UCCx813-5 (Note 4) 26 31 36 kHz

Temperature Stability (Note 9) 2.5 %

Amplitude Peak-to-Peak 2.25 2.40 2.55 V

Oscillator Peak Voltage 2.45 V

UCC2813-0/-1/-2/-3/-4/-5

UCC3813-0/-1/-2/-3/-4/-5

ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for –40°C ≤TA≤+85°C for

UCC2813-x; 0°C ≤TA≤+70°C for UCC3813-x; VCC = 10V (Note 3); RT = 100k from REF to RC; CT=330pF from RC to GND;

0.1µF capacitor from VCC to GND; 0.1µF capacitor from VREF to GND. TA=T

PARAMETER TEST CONDITIONS UCC2813-x

UCC3813-x UNITS

MIN TYP MAX

Error Amplifier Section

Input Voltage COMP = 2.5V; UCCx813-0/-1/-2/-4 2.42 2.50 2.56 V

COMP = 2.0V; UCCx813-3/-5 1.92 2.0 2.05 V

Input Bias Current –22µA

Open Loop Voltage Gain 60 80 dB

COMP Sink Current FB = 2.7V, COMP = 1.1V 0.4 2.5 mA

COMP Source Current FB = 1.8V, COMP = REF – 1.2V –0.2 –0.5 –0.8 mA

Gain Bandwidth Product (Note 9) 2 MHz

PWM Section

Maximum Duty Cycle UCCx813-0/-2/-3 97 99 100 %

UCCx813-1/-4/-5 48 49 50

Minimum Duty Cycle COMP = 0V 0 %

Current Sense Section

Gain (Note 5) 1.10 1.65 1.80 V/V

Maximum Input Signal COMP = 5V (Note 6) 0.9 1.0 1.1 V

Input Bias Current –200 200 nA

CS Blank Time 50 100 150 ns

Over-Current Threshold 1.32 1.55 1.70 V

COMP to CS Offset CS = 0V 0.45 0.90 1.35 V

Output Section

OUT Low Level I = 20mA, all parts 0.1 0.4 V

I = 200mA, all parts 0.35 0.90 V

I = 50mA, VCC = 5V, UCCx813-3/-5 0.15 0.40 V

I = 20mA, VCC = 0V, all parts 0.7 1.2 V

OUT High VSAT

(VCC-OUT) I = –20mA, all parts 0.15 0.40 V

I = –200mA, all parts 1.0 1.9 V

I = –50mA,VCC = 5V, UCCx813-3/-5 0.4 0.9 V

Rise Time CL= 1nF 41 70 ns

Fall Time CL= 1nF 44 75 ns

Undervoltage Lockout Section

Start Threshold (Note 8) UCCx813-0 6.6 7.2 7.8 V

UCCx813-1 8.6 9.4 10.2 V

UCCx813-2/-4 11.5 12.5 13.5 V

UCCx813-3/-5 3.7 4.1 4.5 V

Stop Threshold (Note 8) UCC1813-0 6.3 6.9 7.5 V

UCC1813-1 6.8 7.4 8.0 V

UCCx813-2/-4 7.6 8.3 9.0 V

UCCx813-3/-5 3.2 3.6 4.0 V

Start to Stop Hysteresis UCCx813-0 0.12 0.3 0.48 V

UCCx813-1 1.6 2 2.4 V

UCCx813-2/-4 3.5 4.2 5.1 V

UCCx813-3/-5 0.2 0.5 0.8 V

UCC2813-0/-1/-2/-3/-4/-5

UCC3813-0/-1/-2/-3/-4/-5

ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply for –40°C ≤TA≤+85°C for

UCC2813-x; 0°C ≤TA≤+70°C for UCC3813-x; VCC = 10V (Note 3); RT = 100k from REF to RC; CT=330pF from RC to GND;

0.1µF capacitor from VCC to GND; 0.1µF capacitor from VREF to GND. TA=T

PARAMETER TEST CONDITIONS UCC2813-x

UCC3813-x UNITS

MIN TYP MAX

Soft Start Section

COMP Rise Time FB = 1.8V, Rise from 0.5V to REF–1V 4 ms

Overall Section

Start-up Current VCC < Start Threshold 0.1 0.23 mA

Operating Supply Current FB = 0V, CS = 0V, RC = 0V 0.5 1.2 mA

VCC Internal Zener Voltage ICC = 10mA (Note 8) 12 13.5 15 V

VCC Internal Zener Voltage Minus Start

Threshold Voltage UCCx813-2/-4 0.5 1.0 V

Note 3: Adjust VCC above the start threshold before setting at 10V.

Note 4: Oscillator frequency for the UCCx813-0, UCCx813-2 and UCCx813-3 is the output frequency.

Oscillator frequency for the UCCx813-1, UCCx813-4 and UCCx813-5 is twice the output frequency.

Note 5: Gain is defined by: AVVVV

COMP

CS CS

≤≤008.

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.

COMP: COMP is the output of the error amplifier and the

input of the PWM comparator.

Unlike other devices, the error amplifier in the UCC3813

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 UCC3813 family features built-in full cycle Soft Start.

Soft Start is implemented as a clamp on the maximum

COMP voltage.

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.

CS: CS is the input to the current sense comparators.

The UCC3813 family has two different current sense

comparators: the PWM comparator and an over-current

comparator.

The UCC3813 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 re-

quired on CS. Compared to an external RC filter tech-

nique, the leading-edge blanking provides a smaller

effective 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.

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.

PIN DESCRIPTIONS

UCC2813-0/-1/-2/-3/-4/-5

UCC3813-0/-1/-2/-3/-4/-5

The frequency of oscillation can be estimated with the

following equations:

UCCx813-0/-1/-2/-4:

FRC

=•

15.

UCCx813-3, UCCx813-5:

FRC

=•

10.

where frequency is in Hz, resistance is in Ω, and capaci-

tance is in farads. The recommended range of timing re-

sistors is between 10k and 200k and timing capacitor is

100pF to 1000pF. Never use a timing resistor less than

10k.

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 VCC is below the UVLO threshold.

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 VCC. 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.

VCC: VCC is the power input connection for this device.

In normal operation VCC is powered through a current

limiting resistor. Although quiescent VCC current is very

low, total supply current will be higher, depending on

OUT current. Total VCC current is the sum of quiescent

VCC current and the average OUT current. Knowing the

operating frequency and the MOSFET gate charge (Qg),

average OUT current can be calculated from:

IQF

OUT g

=•

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 VCC is greater than 1V and less than the UVLO

threshold, REF is pulled to ground through a 5kΩresis-

tor. This means that REF can be used as a logic output

indicating power system status. It is important for refer-

ence stability that REF is bypassed to GND with a ce-

ramic capacitor as close to the pin as possible. An

electrolytic capacitor may also be used in addition to the

ceramic capacitor. A minimum of 0.1µF 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.

PIN DESCRIPTIONS (cont.)

Figure 1. Oscillator.

APPLICATION INFORMATION

The UCC3813-0/-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 transistor on-resistance of approximately 125

Ω

. During the fall time, the output

is off and the maximum duty cycle is reduced below 50% or 100% depending on the part number. Larger timing capacitors in-

crease the discharge time and reduce the maximum duty cycle and frequency.

UDG-96139

UCC2813-0/-1/-2/-3/-4/-5

UCC3813-0/-1/-2/-3/-4/-5

4.00

3.98

3.96

3.94

3.92

3.90

3.88

3.86

3.84

3.824 4.2 4.4 4.6 4.8 55.2 5.4 5.6 5.8 6

V (V)

REF

Figure 5. UCC3813-3/-5 V

REF

vs. V

LOAD

= 0.5mA.Figure 2. Error amplifier gain/phase response.

APPLICATION INFORMATION (cont.)

1000

100

1010 100 1000

Oscillator Freq. (kHz)

R(k)

100pF

200pF

330pF

1nF

Figure 6. UCC3813-3/-5 oscillator frequency vs. R

and C

1000

100

1010 100 1000

Oscillator Freq. (kHz)

R(k)

100pF

200pF

330pF

1nF

Figure 3. UCC3813-0/-1/-2/-4 oscillator frequency vs.

and C

95.5

96.5

97.5

98.5

99.5

100

10 100 1000

Oscillator Frequency (kHz)

Maximum Duty Cycle (%)

C = 100pF

C = 200pF

C = 330pF

Figure 4. UCC3813-0/-2/-3 max. duty cycle vs.

oscillator frequency.

46.5

47.5

48.5

49.5

10 100 1000

Oscillator Frequency (kHz)

Maximum Duty Cycle (%)

C = 100pF

C = 200pF

C = 330pF

Figure 7. UCC3813-1/-4/-5 max. duty cycle vs.

oscillator frequency.

UCC2813-0/-1/-2/-3/-4/-5

UCC3813-0/-1/-2/-3/-4/-5

0 100 200 300 400 500 600 700 800 900 1000

Oscillator Frequency (kHz)

I (mA)

V = 10V, 1nF

V = 8V, 1nF

V = 10V, No Load

V = 8V, No Load

Figure 8. UCC3813-0 I

vs. oscillator frequency.

APPLICATION INFORMATION (cont.)

0 100 200 300 400 500 600 700 800 900 1000

Oscillator Frequency (kHz)

I (mA)

V = 10V, 1nF

V = 8V, 1nF

V = 10V, No Load

V = 8V, No Load

Figure 10. UCC3813-5 I

vs. oscillator frequency.

0.6

0.7

0.8

0.9

1.0

1.1

-55-50 -25 0 25 50 75 100 125

Temperature (°C)

COMP to CS Offset (Volts)

Slope = 1.8mV/ C

Figure 11. COMP to CS offset vs. temperature,

CS = 0V.

100

150

200

250

300

350

400

450

500

100 200 300 400 500 600 700 800 900 1000

C (pF)

Dead Time (ns)

UCC1803/5

UCC1800/1/2/4

Figure 9. Dead time vs. C

= 100k.

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