TEXAS INSTRUMENTS UCC28C40, UCC28C41, UCC28C42, UCC28C43, UCC28C44 Technical data

...

UCC28C40, UCC28C41, UCC28C42, UCC28C43, UCC28C44, UCC28C45 UCC38C40, UCC38C41, UCC38C42, UCC38C43, UCC38C44, UCC38C45

SLUS458E -- AUGUST 2001 -- REVISED OCTOBER 2010

BiCMOS LOW-POWER CURRENT-MODE PWM CONTROLLER

FEATURES

D Enhanced Replacement for UC3842A Family

With Pin-to-Pin Compatibility

D 1-MHz Operation D 50-μA Standby Current, 100-μA Maximum D Low Operating Current of 2.3 mA at 52 kHz D Fast 35-ns Cycle-by-Cycle Overcurrent

Limiting

D ±1-A Peak Output Current D Rail-to-Rail Output Swings with 25-ns Rise

and 20-ns Fall Times

D ±1% Initial Trimmed 2.5-V Error Amplifier

Reference

D Trimmed Oscillator Discharge Current D New Under Voltage Lockout Versions D MSOP-8 Package Minimizes Board Space

APPLICATIONS

D Switch-Mode Power Supplies D dc-to-dc Converters D Board Mount Power Modules

DESCRIPTION

UCC38C4x family is a high-performance currentmode PWM controller. It is an enhanced BiCMOS version with pin-for-pin compatibility to the industry standard UC384xA family and UC384x family of PWM controllers. In addition, lower startup voltage versions of 7 V are offered as UCC38C40 and UCC38C41.

Providing necessary features to control fixed frequency, peak current-mode power supplies, this family offers the following performance advantages. The device offers high-frequency operation up to 1 MHz with low start-up and operating currents, thus minimizing start-up loss and low operating power consumption for improved efficiency. The device also features a very fast current-sense-to-output delay time of 35 ns and a ±1 A peak output current capability with improved rise and fall times for driving large external MOSFETs directly.

The UCC38C4x family is offered in 8-pin packages, MSOP (DGK), SOIC (D) and PDIP (P).

FUNCTIONAL BLOCK DIAGRAM

5.0 V

RT/CT

2.5 V +

1COMP

3CS

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications ofTexas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.

VREF

ERROR AMP

Note: Toggle flip--flop used only in UCC38C41, UCC38C44, and UCC38C45.

OSC

VREF

GOOD LOGIC

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UVLO

(NOTE)

7VREF

VDD

5GND

6OUT

UDG--99139

UCC28C40, UCC28C41, UCC28C42, UCC28C43, UCC28C44, UCC28C45

0Cto70C

UCC38C40, UCC38C41, UCC38C42, UCC38C43, UCC38C44, UCC38C45

SLUS458E -- AUGUST 2001 -- REVISED OCTOBER 2010

recommended operating conditions

MIN MAX UNIT

Input voltage, V

Output voltage range, V

Average output current, I

Reference output current, I

Operating junction temperature, T

It is not recommended that the device operate under conditions beyond those specified in this table for extended periods of time.

OUT

OUT(ref)

-- 4 0 105 °C

18 V

200 mA

-- 2 0 mA

absolute maximum ratings over operating free-air temperature (unless otherwise noted)

Supply voltage (VDD) 20 V......................................................................

(MAX ICC) 30 mA..................................................................

Output current, I

peak ±1A...................................................................

OUT

Output energy, capacitive load 5 μJ...............................................................

Voltage rating (COMP, CS, FB) --0.3 V to 6.3 V....................................................

(OUT) --0.3 V to 20 V...............................................................

(RT/CT) --0.3 V to 6.3 V............................................................

(VREF) 7V.......................................................................

Error amplifier output sink current 10 mA..........................................................

Total Power Dissipation at T

=25°C: D package 50 °C/W..........................................

DGK package 120°C/W......................................

P package 65°C/W..........................................

Operating junction temperature range, T Storage temperature range T

stg

-- 5 5 °C to 150°C...........................................

-- 6 5 °C to 150°C....................................................

Lead Temperature (Soldering, 10 seconds) 300°C..................................................

‡

Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

All voltages are with respect to ground. Currents are positive into and negative out of the specified terminals. Consult the Packaging Section of the Databook for thermal limitations and considerations of the package.

AVAILABLE OPTIONS

A=TJ

-- 4 0 °C to 105°C

0°Cto70°C

†

D (SOIC--8) and DGK (MSOP--8) packages are available taped and reeled. Add R suffix to device type (e.g. UCC28C42DR) to order quantities of 2500 devices per reel. Tube quantities are 75 for D packages (SOIC--8) and 80 for DGK package (MSOP--8), and 50 for P package (PDIP-8).

MAXIMUM

DUTY CYCLE

100%

50%

100%

50%

UVLO

ON/OFF

14.5V / 9.0V UCC28C42D UCC28C42P UCC28C42DGK

8.4V / 7.6V UCC28C43D UCC28C43P UCC28C43DGK

7.0V / 6.6V UCC28C40D UCC28C40P UCC28C40DGK

14.5V / 9.0V UCC28C44D UCC28C44P UCC28C44DGK

8.4V / 7.6V UCC28C45D UCC28C45P UCC28C45DGK

7.0V / 6.6V UCC28C41D UCC28C41P UCC28C41DGK

14.5V / 9.0V UCC38C42D UCC38C42P UCC38C42DGK

8.4V / 7.6V UCC38C43D UCC38C43P UCC38C43DGK

7.0V / 6.6V UCC38C40D UCC38C40P UCC38C40DGK

14.5V / 9.0V UCC38C44D UCC38C44P UCC38C44DGK

8.4V / 7.6V UCC38C45D UCC38C45P UCC38C45DGK

7.0V / 6.6V UCC38C41D UCC38C41P UCC38C41DGK

SOIC--8

SMALL OUTLINE

(D){

PDIP--8

PLASTIC DIP

(P)

MSOP--8

SMALL OUTLINE

(DGK){

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UCC28C40, UCC28C41, UCC28C42, UCC28C43, UCC28C44, UCC28C45 UCC38C40, UCC38C41, UCC38C42, UCC38C43, UCC38C44, UCC38C45

SLUS458E -- AUGUST 2001 -- REVISED OCTOBER 2010

electrical characteristics VDD= 15 V (See Note 1), RT=10kΩ,CT=3.3nF,C

=0.1μF and no load

VDD

on the outputs, TA=--40°C to 105°C for the UCC28C4x and TA=0°Cto70°C for the UCC38C4x, TA=TJ(unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Reference Section

Output voltage, initial accuracy TA=25°CI

Line regulation VDD=12Vto18V 0.2 20 mV

Load regulation 1mA to 20mA 3 25 mV

Temperature stability SeeNote2 0.2 0.4 mV/°C

Total output variation SeeNote2 4.82 5.18 V

Output noise voltage 10 Hz to 10 kHz, TA=25°C, SeeNote2 50 μV

Long term stability 1000 hours, TA= 125°C, SeeNote2 5 25 mV

Output short circuit –30 –45 –55 mA

Oscillator Section

Initial accuracy TA=25°C, SeeNote3 50.5 53 55 kHz

Voltage stability VDD=12Vto18V 0.2% 1.0%

Temperature stability T

Amplitude RT/CT Pin peak-to-peak 1.9 V

Discharge current

Error Amplifier Section

Feedback input voltage, initial accuracy V

Feedback input voltage, total variation V

Input bias current VFB=5.0V –0.1 –2.0 μA

Open-loop voltage gain (A

Unity gain bandwidth SeeNote2 1.0 1.5 MHz

Power s upply rejection ratio (PSRR) VDD=12Vto18V 60 dB

Output sink current VFB=2.7V, V

Output source current VFB=2.3V, V

High-level output voltage (VOH) VFB=2.7V, R

Low-level output voltage (VOL) VFB=2.7V, R

Current Sense Section

Gain SeeNote5,6 2.85 3.00 3.15 V/V

Maximum input signal VFB<2.4V 0.9 1.0 1.1 V

Power s upply rejection ratio (PSRR) VDD = 12 V to 18 V, See Note 2, 5 70 dB

Input bias current –0.1 –2.0 μA

CS to output delay 35 70 ns

COMP to CS offset VCS=0V 1.15 V

NOTE: 1. Adjust VDDabove the start threshold before setting at 15 V. NOTE: 2. Ensured by design. Not production tested.

NOTE: 3. Output frequencies of the UCC38C41, UCC38C44 and the UCC38C45 are half the oscillator frequency. NOTE: 4. Oscillator discharge current is measured with R NOTE: 5. Parameter measured at trip point of latch with VFB=0V.

NOTE: 6. Gain is defined as ACS =

) V

VOL

ΔV

to T

MIN

TA=25°C, RT/CT = 2 V, See Note 4 7.7 8.4 9.0 mA

RT/CT = 2 V, See Note 4 7.2 8.4 9.5 mA

COMP

OUT

COM

,0V ≼ VCS≼ 900mV

,SeeNote2 1% 2.5%

MAX

=2.5V, TA=25°C 2.475 2.500 2.525 V

=2.5V, 2.45 2.50 2.55 V

=2Vto4V 65 90 dB

=10kΩ to V

=1mA 4.9 5.0 5.1 V

OUT

=1.1V 2 14 mA

COMP

=5V –0.5 –1.0 mA

COMP

=15ktoGND 5 6.8 V

LOAD

= 15 k to VREF 0.1 1.1 V

LOAD

REF.

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UCC28C40, UCC28C41, UCC28C42, UCC28C43, UCC28C44, UCC28C45

Startthreshol

Minimumoperatingvoltage

UCC38C40, UCC38C41, UCC38C42, UCC38C43, UCC38C44, UCC38C45

SLUS458E -- AUGUST 2001 -- REVISED OCTOBER 2010

electrical characteristics VDD= 15 V (See Note 1), RT=10kΩ,CT=3.3nF,C

=0.1μF and no load

VDD

on the outputs, TA=--40°C to 105°C for the UCC28C4x and TA=0°Cto70°C for the UCC38C4x, TA=TJ(unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Output Section

low (R

OUT

high (R

OUT

Rise tIme TA=25°C, C

Fall time TA=25°C, C

Undervoltage Lockout Section

Start threshold

Minimum operating voltage

PWM Section

Maximum duty cycle

Minimum duty cycle VFB>2.6V 0%

Current Supply Section

Start-up current (I

Operating supply current (IDD) VFB=VCS=0V 2.3 3.0 mA

NOTE 1: Adjust VDDabove the start threshold before setting at 15 V.

pull-down) I

DS(on)

pull-up) I

DS(on)

START-UP

) VDD= Undervoltage lockout start threshold ( --0.5 V) 50 100 μA

= 200 mA 5.5 15

SINK

= 200 mA 10 25

SOURCE

=1nF 25 50

LOAD

=1nF 20 40

LOAD

UCC38C42, UCC38C44 13.5 14.5 15.5

UCC38C43, UCC38C45 7.8 8.4 9.0

UCC38C40, UCC38C41 6.5 7.0 7.5

UCC38C42, UCC38C44 8 9 10

UCC38C43, UCC38C45 7.0 7.6 8.2

UCC38C40, UCC38C41 6.1 6.6 7.1

UCC38C42, UCC38C43, UCC38C40, VFB<2.4V 94% 96%

UCC38C44, UCC38C45, UCC38C41, VFB<2.4V 47% 48%

Ω

PDIP (P) or SOIC (D) PACKAGE

COMP

RT/CT

(TOP VIEW)

VREF VDD OUT GND

COMP

RT/CT

MSOP (DGK) PACKAGE

(TOP VIEW)

VREF VDD OUT GND

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UCC28C40, UCC28C41, UCC28C42, UCC28C43, UCC28C44, UCC28C45 UCC38C40, UCC38C41, UCC38C42, UCC38C43, UCC38C44, UCC38C45

SLUS458E -- AUGUST 2001 -- REVISED OCTOBER 2010

pin assignments

COMP: This pin provides the output of the error amplifier for compensation. In addition, the COMP pin is

frequently used as a control port by utilizing a secondary-side error amplifier to send an error signal across the secondary-primary isolation boundary through an opto-isolator.

CS: The current sense pin is the non-inverting input to the PWM comparator. This is compared to a signal proportional to the error amplifier output voltage. A voltage ramp can be applied to this pin to run the device with a voltage mode control configuration.

FB: This pin is the inverting input to the error amplifier. The non-inverting input to the error amplifier is internally trimmedto2.5V±1%.

GND: Ground return pin for the output driver stage and the logic level controller section.

OUT: The output of the on-chip drive stage. OUT is intended to directly drive a MOSFET. The OUT pin in the

UCC38C40, UCC38C42 and UCC38C43 is the same frequency as the oscillator, and can operate near 100% duty cycle. In the UCC38C41, UCC38C44 and the UCC38C45, the frequency of OUT is one-half that of the oscillator due to an internal T flipflop. This limits the maximum duty cycle to < 50%.

RT/CT: Timing resistor and timing capacitor. The timing capacitor should be connected to the device ground using minimal trace length.

VDD: Power s upply pin for the device. This pin should be bypassed with a 0.1-μF capacitor with minimal trace lengths. Additional capacitance may be needed to provid e hold up power to the device during startup.

VREF: 5-V reference. For stability, the reference should be bypassed with a 0.1-μF capacitor to ground using the minimal trace length possible.

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UCC28C40, UCC28C41, UCC28C42, UCC28C43, UCC28C44, UCC28C45 UCC38C40, UCC38C41, UCC38C42, UCC38C43, UCC38C44, UCC38C45

SLUS458E -- AUGUST 2001 -- REVISED OCTOBER 2010

APPLICATION INFORMATION

This device is a pin-for-pin replacement of the bipolar UC3842 family of controllers, the industry standard PWM controller for single-ended converters. Familiarity with this controller family is assumed.

The UCC28C4x/UCC38C4x series is an enhanced replacement with pin-to-pin compatibility to the bipolar UC284x/UC384x and UC284xA/UC384xA families. The new series offers improved performance when compared to older bipolar devices and other competitive BiCMOS devices with similar functionality. Note that these improvements discussed below generally consist of tighter specification limits that are a subset of the older product ratings, maintaining drop-in capability. In new designs these improvements can be utilized to reduce the component count or enhance circuit performance when compared to the previously available devices.

advantages

This device increases the total circuit efficiency whether operating off-line or in dc input circuits. In off-line applications the low start-up current of this device reduces steady state power dissipation in the startup resistor, and the low operating current maximizes efficiency while running. The low running current also provides an efficiency boost in battery operated supplies.

low voltage operation

Two members of the UCC38C4x family are intended for applications that require a lower start-up voltage than the original family members. The UCC38C40 and UCC38C41 have a turn-on voltage of 7.0 V typical and exhibit hysteresis of 0.4 V for a turn-off voltage of 6.6 V. This reduced start-up voltage enables use in systems with lower voltages, such as 12-V battery systems which are nearly discharged.

high speed operation

The BiCMOS design allows operation at high frequencies that were not feasible in the predecessor bipolar devices. First, the output stage has been redesigned to drive the external power switch in approximately half the time of the earlier devices. Second, the internal oscillator is more robust with less variation as frequency increases. In addition, the current sense to output delay has been reduced by a factor of three, to 45ns typical. These features combine to provide a device capable of reliable high frequency operation.

The UCC38C4x family oscillator is true to the curves of the original bipolar devices at lower frequencies yet extends the frequency programmability range to at least 1MHz. This allows the device to offer pin to pin capability where required yet capable of extending the operational range to the higher frequencies typical of latest applications. When the original UC3842 was released in 1984 most switching supplies operated between 20kHz and 100kHz. Today, the UCC38C4x can be used in designs cover a span roughly ten times higher than those numbers.

start/run current improvements

The start--up current is only 60 μA typical, a significant reduction from the bipolar device’s ratings of 300uA (UC384xA). For operation over the temperature range of --40 to 85°C the UCC28C4x devices offer a maximum startup current of 100 μA, an improvement over competitive BiCMOS devices. This allows the power supply designer to further optimize the selection of the startup resistor value to provide a more efficient design. In applications where low component cost overrides maximum efficiency the low run current of 2.3 mA, typical, may allow the control device to run directly through the single resistor to (+) rail, rather than needing a bootstrap winding on the power transformer, along with a rectifier. The start/run resistor for this case must also pass enough current to allow driving the primary switching MOSFET, which may be a few milliamps in small devices.

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UCC28C40, UCC28C41, UCC28C42, UCC28C43, UCC28C44, UCC28C45 UCC38C40, UCC38C41, UCC38C42, UCC38C43, UCC38C44, UCC38C45

SLUS458E -- AUGUST 2001 -- REVISED OCTOBER 2010

APPLICATION INFORMATION

± 1% initial reference voltage

The BiCMOS internal reference of 2.5 V has an enhanced design and utilizes production trim to allow initial accuracy of ±1% at room temperature and ± 2% over the full temperature range. This can be used to eliminate an external reference in applications that do not require the extreme accuracy afforded by the additional device. This is very useful for nonisolated dc-to-dc applications where the control device is referenced to the same common as the output. It is also applicable in offline designs that regulate on the primary side of the isolation boundary by looking at a primary bias winding, or perhaps from a winding on the output inductor of a buck-derived circuit.

reduced discharge current variation

The original UC3842 oscillator did not have trimmed discharged current, and the parameter was not specified on the datasheet. Since many customers attempted to use the discharge current to set a crude deadtime limit the UC3842A family was released with a trimmed discharge current specified at 25°C. The UCC28C4x/UCC38C4x series now offers even tighter control of this parameter, with approximately ±3% accuracy at 25°C, and less than 10% variation over temperature using the UCC28C4x devices. This level of accuracy can enable a meaningful limit to be programmed, a feature not currently seen in competitive BiCMOS devices. The improved oscillator and reference also contribute to decreased variation in the peak to peak variation in the oscillator waveform, which is often used as the basis for slope compensation for the complete power system.

soft-start

The following diagram provides a typical soft-start circuit for use with the UCC38C42. The values of R and C should be selected to bring the COMP pin up at a controlled rate, limiting the peak current supplied by the power stage. After the soft-start interval is complete the capacitor continues to charge to V

, effectively removing

REF

the PNP transistor from circuit considerations.

The optional diode in parallel with the resistor forces a soft-start each time the PWM goes through UVLO and the reference (V

) goes low. Without the diode,the capacitor otherwise remains charged during a brief loss

REF

of supply or brown-out, and no soft-start is enabled upon reapplication of VIN.

REF

UCC38C42

GND

1COMP

Figure 1

UDG--01072

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UCC28C40, UCC28C41, UCC28C42, UCC28C43, UCC28C44, UCC28C45 UCC38C40, UCC38C41, UCC38C42, UCC38C43, UCC38C44, UCC38C45

SLUS458E -- AUGUST 2001 -- REVISED OCTOBER 2010

APPLICATION INFORMATION

oscillator synchronization

The UCC38C4x oscillator has the same synchronization characteristics as the original bipolar devices. Thus, the information in the Application Note U--100A, UC3842/3/4/5 Provides Low-Cost Current-Mode Control, (TI Literature No. SLUA143) still applies. The application note describes how a small resistor from the timing capacitor-to-ground can offer an insertion point for synchronization to an external clock, (see Figures 2 and 3). Figure 2 shows how the UCC38C42 can be synchronized to an external clock source. This allows precise control of frequency and dead time with a digital pulse train.

REF

RT/C

UCC38C42 PWM

Ω

SYNCHRONIZATION CIRCUIT INPUT

CLOCK

INPUT

PWM

OUT

Figure 2. Oscillator Synchronization Circuit

LOW LOWHIGH

ON .

VCT(ANALOG)

SYNC

(DIGITAL)

COMBINED

ON .OFF .

Figure 3. Synchronization to an External Clock

OUTPUT A

UPPER THRESHOLD

LOWER THRESHOLD

UDG--01069

UPPER THRESHOLD

LOWER THRESHOLD

UDG--01070

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UCC28C40, UCC28C41, UCC28C42, UCC28C43, UCC28C44, UCC28C45 UCC38C40, UCC38C41, UCC38C42, UCC38C43, UCC38C44, UCC38C45

SLUS458E -- AUGUST 2001 -- REVISED OCTOBER 2010

APPLICATION INFORMATION

precautions

The absolute maximum supply voltage is 20 V, including any transients that may be present. If this voltage is exceeded, device damage is likely. This is in contrast to the predecessor bipolar devices, w hich could s urvive up to 30 V.Thus, the supply pin should be decoupled as close to the ground pin as possible. Also, since no clamp is included in the device, the supply pin should be protected from external sources which could exceed the 20 V level.

Careful layout of the printed board has always been a necessity for high frequency power supplies. As the device switching speeds and operating frequencies increase the layout of the converter becomes increasingly important.

This 8-pin device has only a single ground for the logic and power connections. This forces the gate drive current pulses to flow through the s ame ground that the control circuit uses for reference. Thus, the interconnect inductance should be minimized as much as possible. One implication is to place the device (gate driver) circuitry close to the MOSFET it is driving. Note that this can conflict with the need for the error amplifier and the feedback path to be away from the noise generating components.

circuit applications

Figure 4 shows a typical off-line application.

D50

R16

C13

D51

IC3

C52

IC2

R50

C53

L50

C54

R50

C50

C51

R55

R52

R56

R53

R54

AC INPUT

100 Vac -- 240 Vac

EMI FILTER REQUIRED

IC2

R10

RT1

1COMP

2FB

3CS

4RT/CT

BR1

UCC38C44

C12

R11

C18C1A

8REF

7VCC

6OUT

5GND

R12

C55

12 V OUT

5V OUT

SEC COMMON

UDG--01071

Figure 4. Typical Off-Line Application

Figure 5 shows the forward converter with synchronous rectification. This application provides 48 V to 3.3 V at 10 A with over 85% efficiency and uses the UCC38C42 as the secondary-side controller and UCC3961 as the primary-side startup control device.

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UCC28C40, UCC28C41, UCC28C42, UCC28C43, UCC28C44, UCC28C45 UCC38C40, UCC38C41, UCC38C42, UCC38C43, UCC38C44, UCC38C45

SLUS458E -- AUGUST 2001 -- REVISED OCTOBER 2010

APPLICATION INFORMATION

C15

1uF

R22

100

0.22uF

5.6nF

20k

Vcc

OUT

UCC38C4x

50k

R15

C14

1uF

GND

C24

0.1uF

3r3V

C18

4.7uH 4700pF

C21

C17

R20

0.1uF

C20

C19

R21

4700pF

470uF

PWRGND

C13

C26

2uF

BOOT

BTLO

HIDR

0.33

PGND

LODR

Vcc

R23

402

C22

4.7nF

TPS2832

BAR74

R28

100

BAR74

R27

4.7

R26

4.7

R19

21.5k

R16

C23 680pF

REF

COMP2FB3CS4Rt/Ct

C16

R17

BZX84C15LT1

C12

3300pF

20k

R24

R14

R18

7.5k

C11

1500pF

R25

20k

20k 40%

1nF

10k

VinP

C25

0.047uF

32.4k

76.8k

1.5k

1.2k

470uF

5.1k

4.7

13St14

2.4k

VinN

UVS

ucc3961

OVS2SD3SS

C3 10nF

R10

Vdd

0.1uF

1uF

Out

PGnd

4FB5Rt6

R11

0.22uF

8Vs9CS10

Ref7AGnd

46.4k

0.1uF

470pF

100pF

C10

2.7nF

300

R13

200

R12

Figure 5. Forward Converter with Synchronous Rectification Using the UCC38C42

as the Secondary-Side Controller

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