TEXAS INSTRUMENTS UCC1800, UCC1801, UCC1802, UCC1803, UCC1804 Technical data

...

Low-Power BiCMOS Current-Mode PWM

application

INFO

available

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

FEATURES

µA Typical Starting Supply Current

100

•

500

µA Typical Operating Supply

•

Current Operation to 1MHz

•

Internal Soft Start

•

Internal Fault Soft Start

•

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

Internal Leading-Edge Blanking of the

•

Current Sense Signal 1 Amp Totem-Pole Output

•

perature range options, choice of maximum duty cycle, and choice of critical 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

70ns Typical Response from

•

Current-Sense to Gate Drive Output

1.5% Tolerance Voltage Reference

•

• Same Pinout as UC3842 and

make these ideal choices for use in off-line power supplies. The UCC180x series is specified for operation from –55

the UCC280x series is specified for operation from –40 the UCC380x series is specified for operation from 0

Cto+70oC.

UC3842A

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

UCCx800 100% 5V 7.2V 6.9V UCCx801 50% 5V 9.4V 7.4V UCCx802 100% 5V 12.5V 8.3V UCCx803 100% 4V 4.1V 3.6V UCCx804 50% 5V 12.5V 8.3V UCCx805 50% 4V 4.1V 3.6V

C to +125oC,

Cto+85oC, and

BLOCK DIAGRAM

SLUS270C - MARCH 1999 - REVISED JANUARY 2005

UDG92009-3

ABSOLUTE MAXIMUM RATINGS (Note 1)

VCCVoltage (Note 2) ............................ 12.0V

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

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

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

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

Power Dissipation at T Power Dissipation at T Power Dissipation at T

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

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

limiting resistor. Absolute maximum of 12V applies when V that I

does not exceed 30mA (which includes gate

drive current requirement). The resistor should be sized so that the V tions is below 12V but above the turn off threshold.

< +25°C (N or J Package) ..... 1.0W

< +25°C (D Package)........ 0.65W

< +25°C (L Package) .......1.375W

–65°C to +150°C

is powered through a current

is driven from a low impedance source such

voltage, under operating condi

CONNECTION DIAGRAMS

TSSOP-8 (Top View) PW Package

COMP

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

COMP

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

REF

VCC

OUT

GND

REF

TEMPERATURE AND PACKAGE SELECTION

Temperature Range Available Packages

UCC180X –55°C to +125°C J, L UCC280X –40°C to +85°C N, D, PW UCC380X 0°C to +70°C N, D, PW

ORDERING INFORMATION

UCC

P AC KAGE

PRODUCT OPTION

TE MP E RAT UR E R ANG E

LCC-20 (TOP VIEW) L Package

VCC

OUT

GND

PACKAGE PIN FUNCTION

FUNCTION PIN

N/C 1

Comp 2

N/C 3-4

FB 5

N/C 6

CS 7 N/C 8-9 RC 10 N/C 11

PWR GND 12

GND 13

N/C 14

OUT 15

N/C 16

VCC 17

N/C 18-19

REF 20

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

ELECTRICAL CHARACTERISTICS

UCC180x; –40°C ≤ T CT=330pF from RC to GND; 0.1 F capacitor from V

PARAMETER TEST CONDITIONS UCC180X

≤ +85°C for UCC280x; 0°C ≤ TA≤ +70°C for UCC380x; VCC=10V (Note 3); RT=100k from REF to RC;

Unless otherwise stated, these specifications apply for –55°C ≤ TA≤ +125°C for

to GND; 0.1 F capacitor from V

to GND. TA=TJ.

REF

UCC380X UNITS

UCC280X

MIN TYP MAX MIN TYP MAX

Reference Section

Output Voltage T

=+25°C, I=0.2mA, UCCx800/1/2/4 4.925 5.00 5.075 4.925 5.00 5.075 V

=+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 10 30 10 25 mV Line Regulation T

=+25°C,

=10V to Clamp (I

=–55°C to +125°C,

=10V to Clamp (I

VCC

=25mA)

1.9 1.9 mV/V

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 V

UCCx803/5 (Note 7) 3.90 4.00 4.08 3.90 4.00 4.08 V Output Noise Voltage 10Hz ≤ f ≤ 10kHz, T Long Term Stability T

=+125°C, 1000 Hours (Note 9) 5 5 mV

=+25°C (Note 9) 130 130 µV

Output Short Circuit –5 –35 –5 –35 mA

Oscillator Section

Oscillator Frequency UCCx800/1/2/4 (Note 4) 40 46 52 40 46 52 kHz

UCCx803/5 (Note 4) 26 31 36 26 31 36 kHz Temperature Stability (Note 9) 2.5 2.5 % Amplitude peak-to-peak 2.25 2.40 2.55 2.25 2.40 2.55 V Oscillator Peak Voltage 2.45 2.45 V

Error Amplifier Section

Input Voltage COMP=2.5V; UCCx800/1/2/4 2.44 2.50 2.56 2.44 2.50 2.56 V

COMP=2.0V; UCCx803/5 1.95 2.0 2.05 1.95 2.0 2.05 Input Bias Current

–11–11µA

Open Loop Voltage Gain 60 80 60 80 dB COMP Sink Current FB=2.7V, COMP=1.1V 0.3 3.5 0.4 2.5 mA COMP Source Current FB=1.8V, COMP=REF–1.2V –0.2 –0.5 –0.8 –0.2 –0.5 –0.8 mA Gain Bandwidth Product (Note 9) 2 2 MHz

PWM Section

Maximum Duty Cycle UCCx800/2/3 97 99 100 97 99 100 %

UCCx801/4/5 48 49 50 48 49 50 Minimum Duty Cycle COMP=0V 0 0 % 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 V Input Bias Current

–200 200 –200 200 nA

CS Blank Time 50 100 150 50 100 150 ns Over-Current Threshold 1.42 1.55 1.68 1.42 1.55 1.68 V COMP to CS Offset CS=0V 0.45 0.90 1.35 0.45 0.90 1.35 V

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

ELECTRICAL CHARACTERISTICS

UCC180x; –40°C ≤ T CT=330pF from RC to GND; 0.1 F capacitor from V

PARAMETER TEST CONDITIONS UCC180X

≤ +85°C for UCC280x; 0°C ≤ TA≤ +70°C for UCC380x; VCC=10V (Note 3); RT=100k from REF to RC;

Unless otherwise stated, these specifications apply for –55°C ≤ TA≤ +125°C for

to GND; 0.1 F capacitor from V

to GND. TA=TJ.

REF

UCC380X UNITS

UCC280X

Output Section

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

I=200mA, all parts 0.35 0.90 0.35 0.90 V

I=50mA, VCC=5V, UCCx803/5 0.15 0.40 0.15 0.40 V

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

(VCC-OUT)

SAT

I=–20mA, all parts 0.15 0.40 0.15 0.40 V

I=–200mA, all parts 1.0 1.9 1.0 1.9 V

I=–50mA,VCC=5V, UCCx803/5 0.4 0.9 0.4 0.9 V Rise Time C Fall Time C

=1nF 41 70 41 70 ns

=1nF 44 75 44 75 ns

Undervoltage Lockout Section

Start Threshold (Note 8) UCCx800 6.6 7.2 7.8 6.6 7.2 7.8 V

UCCx801 8.6 9.4 10.2 8.6 9.4 10.2 V

UCCx802/4 11.5 12.5 13.5 11.5 12.5 13.5 V

UCCx803/5 3.7 4.1 4.5 3.7 4.1 4.5 V Stop Threshold (Note 8) UCCx1800 6.3 6.9 7.5 6.3 6.9 7.5 V

UCCx1801 6.8 7.4 8.0 6.8 7.4 8.0 V

UCCx802/4 7.6 8.3 9.0 7.6 8.3 9.0 V

UCCx803/5 3.2 3.6 4.0 3.2 3.6 4.0 V

Undervoltage Lockout Section (cont.)

Start to Stop Hysteresis UCCx800 0.12 0.3 0.48 0.12 0.3 0.48 V

UCCx801 1.6 2 2.4 1.6 2 2.4 V

UCCx802/4 3.5 4.2 5.1 3.5 4.2 5.1 V

UCCx803/5 0.2 0.5 0.8 0.2 0.5 0.8 V

Soft Start Section

COMP Rise Time FB=1.8V, Rise from 0.5V to REF–1V 4 10 4 10 ms

Overall Section

Start-up Current V

< Start Threshold 0.1 0.2 0.1 0.2 mA

Operating Supply Current FB=0V, CS=0V 0.5 1.0 0.5 1.0 mA VCC Internal Zener Voltage I VCC Internal Zener Voltage Minus

=10mA (Note 8), (Note 10) 12 13.5 15 12 13.5 15 V

UCCx802/4 (Note 8) 0.5 1.0 0.5 1.0 V

Start Threshold Voltage

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

=≤≤

∆

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. 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 filtering, 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 technique, 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.

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 ca pable of driving the gate of a power MOSFET with peak

currents exceeding ± 750mA. OUT is actively held low when V

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 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

is below the UVLO threshold.

. The output stage also provides a very

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

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:

UCCx803, UCCx805:

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 resistor. This means that REF can be used as a logic output 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 0.1µF 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.

VCC: V

is the power input connection for this device.

In normal operation V limiting resistor. Although quiescent V

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

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

There should be a minimum of 1.0mF in parallel with a

0.1mF ceramic capacitor from V

close to the device

15.

•

10.

•

is powered through a current

current is very

current is the sum of quiescent

to ground located

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

T and CT. The fall time is set by CT and an internal tran

sistor 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.

Figure 1. Oscillator.

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

Figure 2. Error amplifier gain/phase response.

4.00

3.98

3.96

3.94

3.92

REF

3.90

V (V)

3.88

3.86

3.84

3.82 4 4.2 4.4 4.6 4.8

Figure 3. UCC1803/5 V

vs. VCC;I

REF

5.2 5.4 5.6 5.8 6

V (V)

LOAD

= 0.5mA.

1000

100pF

100

200pF

Oscillator Freq. (kHz)

10 100 1000

330pF

1nF

R(k)

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

1000

100

Oscillator Freq. (kHz)

100pF

200pF 330pF

1nF

10 100 1000

R(k)

Figure 5. UCC1803/5 oscillator frequency vs. RTand C

100

99.5 99

98.5 98

97.5 97

96.5

Maximum Duty Cycle (%)

95.5 95

10 100 1000

Oscillator Frequency (kHz)

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

C = 200pF

C = 330pF

oscillator frequency.

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

C = 100pF

49.5

48.5

47.5

Maximum Duty Cycle (%)

46.5 10 100 1000

Oscillator Frequency (kHz)

C = 200pF

C = 330pF

C = 100pF

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

I (mA)

0 100 200 300 400 500 600 700 800 900 1000

Oscillator Frequency (kHz)

V = 10V, 1nF

V = 8V, 1nF

V = 10V, No Load

V = 8V, No Load

Figure 8. UCC1800 ICC vs. oscillator frequency.

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