UCC38C44DGK_技术文档

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SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

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FEATURES

DESCRIPTION

D

Enhanced Replacement for UC3842A Family

With Pin-to-Pin Compatibility

UCC38C4x family is a high-performance current-

mode 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.

D

1-MHz Operation

50-µA Standby Current, 100-µA Maximum

Low Operating Current of 2.3 mA at 52 kHz

Fast 35-ns Cycle-by-Cycle Overcurrent

Limiting

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.

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

Trimmed Oscillator Discharge Current

New Under Voltage Lockout Versions

MSOP-8 Package Minimizes Board Space

APPLICATIONS

D

Switch-Mode Power Supplies

The UCC38C4x family is offered in 8-pin

packages, MSOP (DGK), SOIC (D) and PDIP (P).

dc-to-dc Converters

Board Mount Power Modules

FUNCTIONAL BLOCK DIAGRAM

5.0 V

VREF

8

VREF

7

5

VDD

GND

UVLO

+

VREF

GOOD LOGIC

RT/CT

4

OSC

(NOTE)

T

6

OUT

2.5 V

ERROR AMP

2R

+

S

R

Q

FB

COMP

CS

2

1

3

R

1V

Q

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

UDG−99139

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments

semiconductor products and disclaimers thereto appears at the end of this data sheet.

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Copyright  2003, Texas Instruments Incorporated

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ꢠ ꢤ ꢡ ꢠꢋ ꢚꢮ ꢜꢛ ꢟ ꢧꢧ ꢥꢟ ꢝ ꢟ ꢞ ꢤ ꢠ ꢤ ꢝ ꢡ ꢩ

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1

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ꢀ ꢁꢁꢂ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢂ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢂ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢉ

ꢀ ꢁꢁꢈ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

recommended operating conditions

MIN

MAX

18

UNIT

V

Input voltage, V

DD

Output voltage range, V

OUT

18

V

W

Average output current, I

OUT

200

−20

150

mA

°C

W

Reference output current, I

OUT(ref)

W

Operating junction temperature, T

−55

J

¶

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

}w

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

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

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

Output current, I

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

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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V

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

Total Power Dissipation at T = 25°C: D package (θjc = 22 °C/W, θja = 40 − 70 °C/W) . . . . . . . . . . 650 mW

A

DGK package (θjc = 41 °C/W, θja = 238 − 269 °C/W . . . . . . 350 mW

P package (θjc = 50 °C/W, θja = 110 °C/W . . . . . . . . . . . . . . 850 mW

J

Operating junction temperature range, T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −55°C to 150°C

Storage temperature range T

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −65°C to 150°C

stg

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

SOIC−8

SMALL OUTLINE

(D){

PDIP−8

PLASTIC DIP

(P)

MSOP−8

SMALL OUTLINE

(DGK){

MAXIMUM

DUTY CYCLE

UVLO

ON/OFF

T

A

14.5V / 9.0V

8.4V / 7.6V

7.0V / 6.6V

14.5V / 9.0V

8.4V / 7.6V

7.0V / 6.6V

14.5V / 9.0V

8.4V / 7.6V

7.0V / 6.6V

14.5V / 9.0V

8.4V / 7.6V

7.0V / 6.6V

UCC28C42D

UCC28C43D

UCC28C40D

UCC28C44D

UCC28C45D

UCC28C41D

UCC38C42D

UCC38C43D

UCC38C40D

UCC38C44D

UCC38C45D

UCC38C41D

UCC28C42P

UCC28C43P

UCC28C40P

UCC28C44P

UCC28C45P

UCC28C41P

UCC38C42P

UCC38C43P

UCC38C40P

UCC38C44P

UCC38C45P

UCC38C41P

UCC28C42DGK

UCC28C43DGK

UCC28C40DGK

UCC28C44DGK

UCC28C45DGK

UCC28C41DGK

UCC38C42DGK

UCC38C43DGK

UCC38C40DGK

UCC38C44DGK

UCC38C45DGK

UCC38C41DGK

100%

50%

−40°C to 105°C

100%

50%

0°C to 70°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).

2

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ꢀꢁ ꢁꢂ ꢃ ꢁꢄ ꢅ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢇ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢂ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁ ꢁꢂ ꢃꢁ ꢄꢉ

ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢅ ꢆ ꢀ ꢁꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢂ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁ ꢁꢈ ꢃꢁ ꢄꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

electrical characteristics V

= 15 V (See Note 1), R = 10 kΩ, C = 3.3 nF, C

= 0.1µF and no load

DD

T

A

VDD

on the outputs, T = −40°C to 105°C for the UCC28C4x and T = 0°C to 70°C for the UCC38C4x,

A

T = T (unless otherwise noted)

A

J

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNITS

Reference Section

Output voltage, initial accuracy

Line regulation

T

= 25°C

I

= 1mA

4.9

5.0

5.1

20

V

mV

mV/°C

V

A

OUT

V

= 12 V to 18 V

0.2

3

DD

Load regulation

1mA to 20mA

See Note 2

25

Temperature stability

Total output variation

Output noise voltage

Long term stability

Output short circuit

Oscillator Section

Initial accuracy

0.2

0.4

5.18

See Note 2

4.82

10 Hz to 10 kHz,

1000 hours,

T

A

= 25°C,

See Note 2

50

5

µV

T

A

= 125°C,

25

mV

mA

–30

–45

–55

T

A

= 25°C,

See Note 3

See Note 2

50.5

53

0.2%

1%

55

1.0%

2.5%

kHz

Voltage stability

V

= 12 V to 18 V

DD

Temperature stability

Amplitude

T

MIN

to T ,

MAX

RT/CT Pin peak-to-peak

1.9

V

T

= 25°C,

RT/CT = 2 V,

See Note 4

7.7

7.2

8.4

9.0

9.5

mA

A

Discharge current

RT/CT = 2 V,

8.4

Error Amplifier Section

Feedback input voltage, initial accuracy

Feedback input voltage, total variation

Input bias current

V

= 2.5 V,

T

= 25°C

2.475

2.45

2.500

2.50

–0.1

90

2.525

2.55

–2.0

V

COMP

A

COMP

= 5.0 V

µA

dB

MHz

dB

mA

V

FB

Open-loop voltage gain (A

Unity gain bandwidth

)

= 2 V to 4 V

65

1.0

60

VOL

OUT

See Note 2

1.5

Power supply rejection ratio (PSRR)

Output sink current

V

DD

V

FB

V

FB

V

FB

V

FB

= 12 V to 18 V

= 2.7 V,

V

= 1.1 V

2

14

–1.0

6.8

COMP

Output source current

High-level output voltage (VOH)

Low-level output voltage (VOL)

Current Sense Section

Gain

= 2.3 V,

= 5V

–0.5

5

COMP

= 2.7 V,

R

= 15 k to GND

= 15 k to VREF

LOAD

= 2.7 V,

0.1

1.1

V

See Note 5, 6

V < 2.4 V

2.85

0.9

3.00

1.0

3.15

1.1

V/V

V

Maximum input signal

Power supply rejection ratio (PSRR)

Input bias current

FB

VDD = 12 V to 18 V, See Note 2, 5

70

dB

µA

ns

V

–0.1

35

–2.0

70

CS to output delay

COMP to CS offset

V

= 0 V

1.15

CS

above the start threshold before setting at 15 V.

NOTE: 1. Adjust V

DD

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 = 10 kΩ to V

T

REF.

NOTE: 5. Parameter measured at trip point of latch with V

= 0 V.

FB

DV

COM

NOTE: 6. Gain is defined as ACS +

, 0V ¬ V

¬ 900mV

CS

DV

CS

3

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ꢀ ꢁꢁꢂ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢂ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢂ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢉ

ꢀ ꢁꢁꢈ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

electrical characteristics V

= 15 V (See Note 1), R = 10 kΩ, C = 3.3 nF, C

= 0.1µF and no load

DD

T

A

VDD

on the outputs, T = −40°C to 105°C for the UCC28C4x and T = 0°C to 70°C for the UCC38C4x,

A

T = T (unless otherwise noted)

A

J

PARAMETER

Output Section

TEST CONDITIONS

MIN

TYP

MAX

UNITS

V

low (R

pull-down)

pull-up)

I

= 200 mA

5.5

15

25

50

40

OUT

DS(on)

SINK

Ω

high (R

= 200 mA

10

25

20

OUT

DS(on)

SOURCE

Rise tIme

Fall time

T

= 25°C,

C

= 1 nF

A

LOAD

C

LOAD

ns

T

A

Undervoltage Lockout Section

UCC38C42, UCC38C44

UCC38C43, UCC38C45

UCC38C40, UCC38C41

UCC38C42, UCC38C44

UCC38C43, UCC38C45

UCC38C40, UCC38C41

13.5

14.5

8.4

7.0

9

15.5

9.0

7.5

10

7.8

6.5

8

Start threshold

V

7.0

6.1

7.6

6.6

8.2

7.1

Minimum operating voltage

PWM Section

UCC38C42, UCC38C43, UCC38C40, V

UCC38C44, UCC38C45, UCC38C41, V

< 2.4 V

94%

47%

96%

48%

FB

Maximum duty cycle

FB

Minimum duty cycle

V

FB

> 2.6 V

0%

Current Supply Section

Start-up current (I

)

V

= Undervoltage lockout start threshold (−0.5 V)

50

100

3.0

µA

START-UP

DD

Operating supply current (I

)

= V

CS

= 0 V

2.3

mA

DD

FB

NOTE 1: Adjust V

DD

above the start threshold before setting at 15 V.

PDIP (P) or SOIC (D) PACKAGE

(TOP VIEW)

MSOP (DGK) PACKAGE

(TOP VIEW)

COMP

FB

VREF

VDD

OUT

GND

8

7

6

5

1

2

3

4

COMP

FB

VREF

VDD

OUT

GND

1

2

3

4

8

7

6

5

CS

RT/CT

4

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ꢀꢁ ꢁꢂ ꢃ ꢁꢄ ꢅ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢇ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢂ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁ ꢁꢂ ꢃꢁ ꢄꢉ

ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢅ ꢆ ꢀ ꢁꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢂ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁ ꢁꢈ ꢃꢁ ꢄꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

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

trimmed to 2.5 V 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 supply 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 provide 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.

5

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ꢀ ꢁꢁꢈ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

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.

6

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ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢅ ꢆ ꢀ ꢁꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢂ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁ ꢁꢈ ꢃꢁ ꢄꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

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

the PNP transistor from circuit considerations.

, effectively removing

REF

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.

8

1

V

REF

UCC38C42

COMP

GND

5

Figure 1

UDG−01072

7

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ꢀ ꢁꢁꢈ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

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.

8

4

V

REF

R

T

SYNCHRONIZATION

CIRCUIT INPUT

R / C

T

C

T

UCC38C42

PWM

W

24

UDG−01069

Figure 2. Oscillator Synchronization Circuit

UPPER THRESHOLD

LOWER THRESHOLD

CLOCK

INPUT

LOW

HIGH

OFF .

LOW

ON .

PWM

OUT

ON .

OUTPUT A

V_CT(ANALOG)

UPPER THRESHOLD

V_CT

LOWER THRESHOLD

V_SYNC(DIGITAL)

COMBINED

UDG−01070

Figure 3. Synchronization to an External Clock

8

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ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢅ ꢆ ꢀ ꢁꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢂ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁ ꢁꢈ ꢃꢁ ꢄꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

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, which could survive

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 same 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

F1

12 V

OUT

T1

R10

C52

C55

C3

D2

C12

AC INPUT

100 Vac − 240 Vac

EMI FILTER

+

R56

BR1

L50

R11

D51

REQUIRED

C1A

C18

5 V

R12

OUT

RT1

C53

C54

D6

R55

C5

SEC

COMMON

R6

R50

UCC38C44

R16

1

2

3

4

COMP REF

8

7

6

5

IC2

Q1

IC2

FB

CS

VCC

OUT

R53

C50

R52

C13

C51

R50

RT/CT GND

K

IC3

A

R

R54

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.

9

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ꢀ ꢁꢁꢂ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢂ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢂ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢉ

ꢀ ꢁꢁꢈ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

APPLICATION INFORMATION

+

Figure 5. Forward Converter with Synchronous Rectification Using the UCC38C42

as the Secondary-Side Controller

10

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ꢀꢁ ꢁꢂ ꢃ ꢁꢄ ꢅ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢇ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢂ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁ ꢁꢂ ꢃꢁ ꢄꢉ

ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢅ ꢆ ꢀ ꢁꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢂ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁ ꢁꢈ ꢃꢁ ꢄꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

TYPICAL CHARACTERISTICS

OSCILLATOR FREQUENCY

OSCILLATOR DISCHARGE CURRENT

vs

TIMING RESISTANCE AND CAPACITANCE

TEMPERATURE

9.5

9.0

8.5

10 M

1 M

CT = 220 pF

CT = 470 pF

CT = 1 nF

100 k

10 k

1 k

8.0

7.5

7.0

CT = 4.7 nF

CT = 2.2 nF

1 k

10 k

100 k

−50

−25

0

25

50

75

100

125

T

J

− Temperature − °C

R

− Timing Resistance − W

T

Figure 6

Figure 7

COMP to CS OFFSET VOLTAGE (with CS = 0)

ERROR AMPLIFIER

FREQUENCY RESPONSE

vs

TEMPERATURE

100

1.8

200

180

1.6

1.4

90

80

70

60

50

40

30

20

10

0

160

140

GAIN

1.2

1.0

0.8

0.6

0.4

0.2

0.0

120

100

80

60

40

PHASE

MARGIN

20

0

1

10

100

1 k 10 k 100 k 1 M 10 M

−50

−25

0

25

50

75

100

125

f − Frequency − Hz

T

J

− Temperature − °C

Figure 8

Figure 9

11

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ꢀ ꢁꢁꢂ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢂ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢂ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢉ

ꢀ ꢁꢁꢈ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

TYPICAL CHARACTERISTICS

REFERENCE VOLTAGE

vs

ERROR AMPLIFIER REFERENCE VOLTAGE

vs

TEMPERATURE

2.55

2.54

5.05

5.04

5.03

5.02

5.01

2.53

2.52

2.51

2.50

2.49

5.00

4.99

4.98

4.97

4.96

4.95

2.48

2.47

2.46

2.45

−50

−25

0

25

50

75

100

125

−50

−25

0

25

50

75

100

125

T

J

− Temperature − °C

T

J

− Temperature − °C

Figure 11

Figure 10

REFERENCE SHORT-CIRCUIT CURRENT

ERROR AMPLIFIER INPUT BIAS CURRENT

vs

TEMPERATURE

200

−35

−37

−39

−41

−43

−45

−47

−49

−51

−53

−55

150

100

50

0

−50

−100

−150

−200

−50

−25

0

25

− Temperature − °C

J

50

75

100

125

−50

−25

0

T

25

50

75

100

125

T

− Temperature − °C

J

Figure 13

Figure 12

12

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ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢅ ꢆ ꢀ ꢁꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢂ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁ ꢁꢈ ꢃꢁ ꢄꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

TYPICAL CHARACTERISTICS

UNDERVOLTAGE LOCKOUT

vs

TEMPERATURE (UCC38C43 & UCC38C45)

TEMPERATURE (UCC38C42 & UCC38C44)

16

9.0

8.8

UVLO

ON

15

14

13

8.6

8.4

8.2

8.0

7.8

7.6

7.4

7.2

7.0

UVLO

ON

12

11

UVLO

OFF

10

9

8

UVLO

OFF

7

6

−50

−25

0

25

50

75

100

125

−50

−25

0

25

50

75

100

125

T

J

− Temperature − °C

T

J

− Temperature − °C

Figure 14

Figure 15

UNDERVOLTAGE LOCKOUT

vs

TEMPERATURE (UCC38C40 & UCC38C41)

7.3

7.2

UVLO

ON

7.1

7.0

6.9

6.8

6.7

6.6

6.5

6.4

UVLO

OFF

6.3

−50

−25

0

25

50

75

100

125

T

J

− Temperature − °C

Figure 16

13

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ꢀ ꢁꢁꢂ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢂ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢂ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢉ

ꢀ ꢁꢁꢈ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

TYPICAL CHARACTERISTICS

SUPPLY CURRENT

vs

TEMPERATURE

SUPPLY CURRENT

vs

OSCILLATOR FREQUENCY

3.0

2.9

25

20

15

10

1-nF LOAD

2.8

2.7

2.6

2.5

2.4

NO LOAD

2.3

2.2

5

0

2.1

2.0

−50

−25

0

25

50

75

100

125

0 k

200 k

400 k

600 k

800 k

1 M

f − Frequency − Hz

T

J

− Temperature − °C

Figure 17

Figure 18

OUTPUT RISE TIME AND FALL TIME

MAXIMUM DUTY CYCLE

vs

TEMPERATURE

OSCILLATOR FREQUENCY

40

100

10% to 90%

V

DD

= 12 V

35

CT = 220 pF

tr

90

80

(1 nF)

30

25

20

tf

(1 nF)

70

60

CT = 1 nF

15

10

50

0

500

1000

1500

−50

−25

0

25

50

75

100

125

2000

2500

T

J

− Temperature − °C

f − Frequency − kHz

Figure 19

Figure 20

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ꢀꢁ ꢁꢂ ꢃ ꢁꢄ ꢅ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢇ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢂ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁ ꢁꢂ ꢃꢁ ꢄꢉ

ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢅ ꢆ ꢀ ꢁꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢂ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁ ꢁꢈ ꢃꢁ ꢄꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

TYPICAL CHARACTERISTICS

MAXIMUM DUTY CYCLE

vs

MAXIMUM DUTY CYCLE

vs

TEMPERATURE

100

98

96

94

92

90

50

UCC38C40

UCC38C42

UCC38C43

UCC38C41

UCC38C44

UCC38C45

49

48

47

46

45

−50

−25

0

25

50

75

100

125

−50

−25

0

25

50

75

100

125

T

J

− Temperature − °C

T

J

− Temperature − °C

Figure 21

Figure 22

CURRENT SENSE THRESHOLD VOLTAGE

CS TO OUT DELAY TIME

vs

TEMPERATURE

1.10

70

65

60

55

50

45

40

35

30

1.05

1.00

0.95

0.90

−50

−25

0

25

50

75

100

125

−50

−25

0

T

25

50

75

100

125

T

J

− Temperature − °C

J

Figure 23

Figure 24

15

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ꢀ

ꢁꢁ

ꢂ

ꢃ

ꢁ

ꢄꢅ

ꢆ

ꢀ

ꢁ

ꢂ

ꢃ

ꢁ

ꢄ

ꢇ

ꢆ

ꢀ

ꢁ

ꢂ

ꢃ

ꢁ

ꢄ

ꢂ

ꢆ

ꢀ

ꢁ

ꢂ

ꢃꢁ

ꢄ

ꢈ

ꢆ

ꢀ

ꢁ

ꢂ

ꢃꢁ

ꢄ

ꢆ

ꢀ

ꢁ

ꢂ

ꢃꢁ

ꢄ

ꢉ

ꢀ

ꢁꢁ

ꢈ

ꢃ

ꢁ

ꢄꢅ

ꢆ

ꢀ

ꢁ

ꢈ

ꢃ

ꢁ

ꢄ

ꢇ

ꢆ

ꢀ

ꢁ

ꢈ

ꢃ

ꢁ

ꢄ

ꢂ

ꢆ

ꢀ

ꢁ

ꢈ

ꢃ

ꢁ

ꢄ

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ꢈ

ꢃꢁ

ꢄ

ꢆ

ꢀ

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ꢃꢁ

ꢄ

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SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

MECHANICAL DATA

D (SOIC)

PLASTIC SMALL-OUTLINE PACKAGE

Note: UCC38C4x is offered in an 8-pin package ONLY.

14 PINS SHOWN

0.050 (1,27)

0.020 (0,51)

0.010 (0,25)

M

0.014 (0,35)

14

8

0.008 (0,20) NOM

0.244 (6,20)

0.228 (5,80)

0.157 (4,00)

0.150 (3,81)

Gage Plane

0.010 (0,25)

1

7

0°−ā8°

0.044 (1,12)

0.016 (0,40)

A

Seating Plane

0.004 (0,10)

0.010 (0,25)

0.004 (0,10)

0.069 (1,75) MAX

PINS **

8

14

16

DIM

0.197

(5,00)

0.344

(8,75)

0.394

(10,00)

A MAX

0.189

(4,80)

0.337

(8,55)

0.386

(9,80)

A MIN

4040047/D 10/96

NOTES: A. All linear dimensions are in inches (millimeters).

B. This drawing is subject to change without notice.

C. Body dimensions do not include mold flash or protrusion, not to exceed 0.006 (0,15).

D. Falls within JEDEC MS-012

16

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ꢀ

ꢁ

ꢂ

ꢃ

ꢁ

ꢄ

ꢅ

ꢆ

ꢀ

ꢁ

ꢂ

ꢃ

ꢁ

ꢄ

ꢇ

ꢆ

ꢀ

ꢁ

ꢂ

ꢃꢁ

ꢄ

ꢂ

ꢆ

ꢀ

ꢁ

ꢂ

ꢃꢁ

ꢄ

ꢈ

ꢆ

ꢀ

ꢁ

ꢂ

ꢃꢁ

ꢄ

ꢆ

ꢀ

ꢁ

ꢁꢂ

ꢃ

ꢁ

ꢄ

ꢉ

ꢀ

ꢁ

ꢈ

ꢃ

ꢁ

ꢄ

ꢅ

ꢆ

ꢀ

ꢁ

ꢈ

ꢃ

ꢁ

ꢄ

ꢇ

ꢆ

ꢀ

ꢁ

ꢈ

ꢃꢁ

ꢄ

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ꢈ

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ꢈ

ꢆ

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ꢄ

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ꢀ

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ꢁꢈ

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ꢁ

ꢄ

ꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

MECHANICAL DATA

DGK (R-PDSO-G8)

PLASTIC SMALL-OUTLINE PACKAGE

0,38

0,25

M

0,65

8

0,25

5

0,15 NOM

3,05

2,95

4,98

4,78

Gage Plane

0,25

0°−ā6°

1

4

0,69

3,05

2,95

0,41

Seating Plane

0,10

0,15

0,05

1,07 MAX

4073329/B 04/98

NOTES: A. All linear dimensions are in millimeters.

B. This drawing is subject to change without notice.

C. Body dimensions do not include mold flash or protrusion.

D. Falls within JEDEC MO-187

17

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ꢀ ꢁꢁꢂ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢂ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢂ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢈ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢂ ꢃꢁ ꢄ ꢉ

ꢀ ꢁꢁꢈ ꢃ ꢁ ꢄꢅ ꢆ ꢀ ꢁ ꢁꢈ ꢃ ꢁꢄ ꢇ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢂ ꢆ ꢀꢁ ꢁꢈ ꢃ ꢁꢄ ꢈ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢄ ꢆ ꢀꢁꢁ ꢈ ꢃꢁ ꢄ ꢉ

SLUS458C − AUGUST 2001 − REVISED SEPTEMBER 2003

MECHANICAL DATA

P (PDIP)

PLASTIC DUAL-IN-LINE

0.400 (10,60)

0.355 (9,02)

8

5

0.260 (6,60)

0.240 (6,10)

1

4

0.070 (1,78) MAX

0.325 (8,26)

0.300 (7,62)

0.020 (0,51) MIN

0.015 (0,38)

Gage Plane

0.200 (5,08) MAX

Seating Plane

0.010 (0,25) NOM

0.125 (3,18) MIN

0.100 (2,54)

0.021 (0,53)

0.430 (10,92)

MAX

0.010 (0,25)

M

0.015 (0,38)

4040082/D 05/98

NOTES: A. All linear dimensions are in inches (millimeters).

B. This drawing is subject to change without notice.

C. Falls within JEDEC MS-001

18

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enhancements, improvements, and other changes to its products and services at any time and to discontinue

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TI warrants performance of its hardware products to the specifications applicable at the time of sale in

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TI assumes no liability for applications assistance or customer product design. Customers are responsible for

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amplifier.ti.com

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dsp.ti.com

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Digital Control

Military

www.ti.com/broadband

www.ti.com/digitalcontrol

www.ti.com/military

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Logic

interface.ti.com

logic.ti.com

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Microcontrollers

power.ti.com

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Security

www.ti.com/opticalnetwork

www.ti.com/security

www.ti.com/telephony

www.ti.com/video

microcontroller.ti.com

Telephony

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Wireless

www.ti.com/wireless

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型号：	UCC38C44DGK
厂家：	TEXAS INSTRUMENTS
描述：	BICMOS LOW POWER CURRENT MODE PWM CONTROLLER BiCMOS低功耗电流模式PWM控制器稳压器开关式稳压器或控制器电源电路开关式控制器光电二极管信息通信管理
文件：	总19页 (文件大小：295K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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