MOTOROLA UC3842ADR2, UC3842AD, UC2843AN, UC2842AN, UC2843ADR2 Datasheet

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High Performance

Current Mode Controllers

The UC3842A, UC3843A series of high performance fixed frequency current mode controllers are specifically designed for off±line and dc±to±dc converter applications offering the designer a cost effective solution with minimal external components. These integrated circuits feature a trimmed oscillator for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator, and a high current totem pole output ideally suited for driving a power MOSFET.

Also included are protective features consisting of input and reference undervoltage lockouts each with hysteresis, cycle±by±cycle current limiting, programmable output deadtime, and a latch for single pulse metering.

These devices are available in an 8±pin dual±in±line plastic package as well as the 14±pin plastic surface mount (SO±14). The SO±14 package has separate power and ground pins for the totem pole output stage.

The UCX842A has UYLO thresholds of 16 V (on) and 10 V (off), ideally suited for off±line converters. The UCX843A is tailored for lower voltage applications having UVLO thresholds of 8.5 V (on) and 7.6 V (off).

Trimmed Oscillator Discharge Current for Precise Duty Cycle Control

Current Mode Operation to 500 kHz

Automatic Feed Forward Compensation

Latching PWM for Cycle±By±Cycle Current Limiting

Internally Trimmed Reference with Undervoltage Lockout

High Current Totem Pole Output

Undervoltage Lockout with Hysteresis

Low Startup and Operating Current

Direct Interface with Motorola SENSEFET Products

 

 

Simplified Block Diagram

 

 

 

 

 

 

VCC

7(12)

Vref

 

 

5.0V

VCC

 

 

 

Reference

Undervoltage

8(14)

R

 

Lockout

 

 

 

R

 

Vref

 

V

 

Undervoltage

 

C

 

 

Lockout

 

7(11)

RTCT

 

Oscillator

 

 

Output

 

 

 

 

6(10)

4(7)

 

 

Latching

 

Voltage

 

 

 

Power

 

 

PWM

 

Feedback

+

 

 

 

Ground

Input

±

 

 

 

5(8)

2(3)

Error

 

 

 

Current

Output

Amplifier

 

 

 

Sense

Compensation

 

 

 

 

3(5) Input

1(1)

 

 

 

 

 

 

 

 

 

 

 

Gnd

5(9)

 

 

Pin numbers in parenthesis are for the D suffix SO±14 package.

Order this document by UC3842A/D

UC3842A, 43A UC2842A, 43A

HIGH PERFORMANCE

CURRENT MODE

CONTROLLERS

N SUFFIX

PLASTIC PACKAGE

CASE 626

 

8

 

1

D SUFFIX

 

PLASTIC PACKAGE

 

CASE 751A

14

(SO±14)

1

PIN CONNECTIONS

Compensation

 

1

 

 

 

8

 

Vref

 

 

 

 

 

 

 

 

 

Voltage Feedback

 

2

 

 

 

7

 

VCC

 

 

 

 

 

 

 

 

 

Current Sense

 

3

 

 

 

6

 

Output

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RT/CT

4

 

 

5

 

Gnd

 

 

 

 

 

(Top View)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Compensation

1

 

 

 

14

 

Vref

 

 

 

 

 

 

 

 

 

 

 

NC

2

 

 

 

13

 

NC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Voltage Feedback

3

 

 

 

12

 

VCC

 

 

 

 

 

 

 

 

 

 

NC

4

 

 

 

11

 

VC

 

 

 

 

 

 

 

 

Current Sense

5

 

 

 

10

 

Output

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NC

6

 

 

 

9

 

Gnd

 

RT/CT

 

 

 

 

 

 

Power Ground

 

 

 

 

 

 

 

 

7

 

 

 

8

 

 

 

 

 

 

(Top View)

 

 

 

 

 

 

 

 

 

 

 

 

ORDERING INFORMATION

 

 

 

 

 

 

 

 

 

 

 

 

Operating

 

 

 

Device

Temperature Range

 

Package

 

 

 

 

 

 

 

 

 

 

UC3842AD

 

 

 

 

 

 

 

 

SO±14

 

 

 

 

 

 

 

 

 

 

UC3843AD

TA = 0° to +70°C

 

 

SO±14

 

 

 

 

UC3842AN

 

 

Plastic

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

UC3843AN

 

 

 

 

 

 

 

 

Plastic

 

 

 

 

 

 

 

 

 

 

UC2842AD

 

 

 

 

 

 

 

 

SO±14

 

 

 

 

 

 

 

 

 

 

UC2843AD

TA = ± 25° to +85°C

 

SO±14

 

 

 

UC2842AN

 

Plastic

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

UC2843AN

 

 

 

 

 

 

 

 

Plastic

 

 

 

 

 

 

 

 

 

 

Motorola, Inc. 1996

Rev 1

UC3842A, 43A UC2842A, 43A

MAXIMUM RATINGS

Rating

 

Symbol

 

 

Value

 

Unit

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Total Power Supply and Zener Current

 

(ICC + IZ)

 

30

 

 

 

mA

 

 

 

 

 

Output Current, Source or Sink (Note 1)

 

 

IO

 

1.0

 

 

 

A

 

 

 

 

 

Output Energy (Capacitive Load per Cycle)

 

 

W

 

5.0

 

 

 

μJ

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Current Sense and Voltage Feedback Inputs

 

 

Vin

 

± 0.3 to + 5.5

 

V

 

 

 

 

 

Error Amp Output Sink Current

 

 

IO

 

10

 

 

 

mA

 

 

 

 

 

Power Dissipation and Thermal Characteristics

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

D Suffix, Plastic Package

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Maximum Power Dissipation @ TA = 25°C

 

 

PD

 

862

 

 

mW

 

 

 

 

 

Thermal Resistance, Junction±to±Air

 

 

RθJA

 

145

 

 

°C/W

 

 

 

 

 

N Suffix, Plastic Package

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Maximum Power Dissipation @ TA = 25°C

 

 

PD

 

1.25

 

 

 

W

 

 

 

 

 

Thermal Resistance, Junction±to±Air

 

 

RθJA

 

100

 

 

°C/W

 

 

 

 

 

Operating Junction Temperature

 

 

TJ

 

+ 150

 

 

 

°C

 

 

 

 

 

Operating Ambient Temperature

 

 

TA

 

 

 

 

 

 

°C

 

 

 

 

 

UC3842A, UC3843A

 

 

 

 

 

0 to + 70

 

 

 

 

 

 

 

 

 

UC2842A, UC2843A

 

 

 

 

 

± 25 to + 85

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Storage Temperature Range

 

 

Tstg

 

± 65 to + 150

 

°C

 

 

 

 

 

ELECTRICAL CHARACTERISTICS (VCC = 15 V, [Note 2], RT = 10 k, CT = 3.3 nF, TA = Tlow to Thigh [Note 3],

 

 

unless otherwise noted.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

UC284XA

 

UC384XA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Characteristics

 

Symbol

 

Min

 

Typ

 

Max

Min

Typ

Max

Unit

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

REFERENCE SECTION

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reference Output Voltage (IO = 1.0 mA, TJ = 25°C)

 

Vref

 

 

4.95

 

5.0

 

5.05

4.9

5.0

5.1

V

Line Regulation (VCC = 12 V to 25 V)

 

Regline

 

±

 

2.0

 

20

±

2.0

20

mV

Load Regulation (IO = 1.0 mA to 20 mA)

 

Regload

 

±

 

3.0

 

25

±

3.0

25

mV

Temperature Stability

 

TS

 

 

±

 

0.2

 

±

±

0.2

±

mV/°C

Total Output Variation over Line, Load, Temperature

 

Vref

 

 

4.9

 

±

 

5.1

4.82

±

5.18

V

Output Noise Voltage (f = 10 Hz to 10 kHz, TJ = 25°C)

 

Vn

 

 

±

 

50

 

±

±

50

±

μV

Long Term Stability (TA = 125°C for 1000 Hours)

 

S

 

 

±

 

5.0

 

±

±

5.0

±

mV

Output Short Circuit Current

 

ISC

 

 

± 30

 

± 85

 

± 180

± 30

± 85

± 180

mA

OSCILLATOR SECTION

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Frequency

 

fosc

 

 

 

 

 

 

 

 

 

 

 

 

kHz

TJ = 25°C

 

 

 

 

47

 

52

 

57

47

52

57

 

TA = Tlow to Thigh

 

 

 

 

46

 

±

 

60

46

±

60

 

Frequency Change with Voltage (VCC = 12 V to 25 V)

 

fosc/

V

 

±

 

0.2

 

1.0

±

0.2

1.0

%

Frequency Change with Temperature

 

fosc/

T

 

±

 

5.0

 

±

±

5.0

±

%

TA = Tlow to Thigh

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Oscillator Voltage Swing (Peak±to±Peak)

 

Vosc

 

 

±

 

1.6

 

±

±

1.6

±

V

Discharge Current (Vosc = 2.0 V)

 

Idischg

 

 

 

 

 

 

 

 

 

 

 

mA

TJ = 25°C

 

 

 

 

7.5

 

8.4

 

9.3

7.5

8.4

9.3

 

TA = Tlow to Thigh

 

 

 

 

7.2

 

±

 

9.5

7.2

±

9.5

 

NOTES: 1. Maximum Package power dissipation limits must be observed.

2.Adjust VCC above the Startup threshold before setting to 15 V.

3.Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible

Tlow = 0°C for UC3842A, UC3843A

Thigh = +70°C for UC3842A, UC3843A

±25°C for UC2842A, UC2843A

+85°C for UC2842A, UC2843A

2

MOTOROLA ANALOG IC DEVICE DATA

5. Comparator gain is defined as: AV

UC3842A, 43A UC2842A, 43A

ELECTRICAL CHARACTERISTICS (VCC = 15 V, [Note 2], RT = 10 k, CT = 3.3 nF, TA = Tlow to Thigh [Note 3], unless otherwise noted.)

 

 

 

UC284XA

 

 

UC384XA

 

 

 

 

 

 

 

 

 

 

 

Characteristics

Symbol

Min

Typ

Max

Min

Typ

Max

Unit

 

 

 

 

 

 

 

 

 

ERROR AMPLIFIER SECTION

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Voltage Feedback Input (VO = 2.5 V)

VFB

2.45

2.5

2.55

2.42

2.5

2.58

V

Input Bias Current (VFB = 2.7 V)

IIB

±

±0.1

±1.0

±

±0.1

±2.0

μA

Open Loop Voltage Gain (VO = 2.0 V to 4.0 V)

AVOL

65

90

±

65

90

±

dB

Unity Gain Bandwidth (TJ = 25°C)

BW

0.7

1.0

±

0.7

1.0

±

MHz

Power Supply Rejection Ratio (VCC = 12 V to 25 V)

PSRR

60

70

±

60

70

±

dB

Output Current

 

 

 

 

 

 

 

mA

Sink (VO = 1.1 V, VFB = 2.7 V)

ISink

2.0

12

±

2.0

12

±

 

Source (VO = 5.0 V, VFB = 2.3 V)

ISource

±0.5

±1.0

±

±0.5

±1.0

±

 

Output Voltage Swing

 

 

 

 

 

 

 

V

High State (RL = 15 k to ground, VFB = 2.3 V)

VOH

5.0

6.2

±

5.0

6.2

±

 

Low State (RL = 15 k to Vref, VFB = 2.7 V)

VOL

±

0.8

1.1

±

0.8

1.1

 

CURRENT SENSE SECTION

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Current Sense Input Voltage Gain (Notes 4 & 5)

AV

2.85

3.0

3.15

2.85

3.0

3.15

V/V

Maximum Current Sense Input Threshold (Note 4)

Vth

0.9

1.0

1.1

0.9

1.0

1.1

V

Power Supply Rejection Ratio

PSRR

 

 

 

 

 

 

dB

VCC = 12 to 25 V (Note 4)

 

±

70

±

±

70

±

 

Input Bias Current

IIB

±

±2.0

±10

±

±2.0

±10

μA

Propagation Delay (Current Sense Input to Output)

tPLH(in/out)

±

150

300

±

150

300

ns

OUTPUT SECTION

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Output Voltage

 

 

 

 

 

 

 

V

Low State (ISink = 20 mA)

VOL

±

0.1

0.4

±

0.1

0.4

 

(ISink = 200 mA)

 

±

1.6

2.2

±

1.6

2.2

 

High State (ISink = 20 mA)

VOH

13

13.5

±

13

13.5

±

 

(ISink = 200 mA)

 

12

13.4

±

12

13.4

±

 

Output Voltage with UVLO Activated

VOL(UVLO)

 

 

 

 

 

 

V

VCC = 6.0 V, ISink = 1.0 mA

 

±

0.1

1.1

±

0.1

1.1

 

Output Voltage Rise Time (CL = 1.0 nF, TJ = 25°C)

tr

±

50

150

±

50

150

ns

Output Voltage Fall Time (CL = 1.0 nF, TJ = 25°C)

tf

±

50

150

±

50

150

ns

UNDERVOLTAGE LOCKOUT SECTION

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Startup Threshold

Vth

 

 

 

 

 

 

V

UCX842A

 

15

16

17

14.5

16

17.5

 

UCX843A

 

7.8

8.4

9.0

7.8

8.4

9.0

 

 

 

 

 

 

 

 

 

 

Minimum Operating Voltage After Turn±On

VCC(min)

 

 

 

 

 

 

V

UCX842A

 

9.0

10

11

8.5

10

11.5

 

UCX843A

 

7.0

7.6

8.2

7.0

7.6

8.2

 

 

 

 

 

 

 

 

 

 

PWM SECTION

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Duty Cycle

 

 

 

 

 

 

 

%

Maximum

DCmax

94

96

±

94

96

±

 

Minimum

DCmin

±

±

0

±

±

0

 

TOTAL DEVICE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Power Supply Current (Note 2)

ICC

 

 

 

 

 

 

mA

Startup:

 

 

 

 

 

 

 

 

(VCC = 6.5 V for UCX843A,

 

±

0.5

1.0

±

0.5

1.0

 

14 V for UCX842A) Operating

 

±

12

17

±

12

17

 

 

 

 

 

 

 

 

 

 

Power Supply Zener Voltage (ICC = 25 mA)

VZ

30

36

±

30

36

±

V

NOTES: 2. Adjust VCC above the Startup threshold before setting to 15 V.

3. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible

Tlow = 0°C for UC3842A, UC3843A

Thigh = +70°C for UC3842A, UC3843A

±25°C for UC2842A, UC2843A

+85°C for UC2842A, UC2843A

4. This parameter is measured at the latch trip point with VFB = 0 V. V Output Compensation

V Current Sense Input

MOTOROLA ANALOG IC DEVICE DATA

3

 

MOTOROLA UC3842ADR2, UC3842AD, UC2843AN, UC2842AN, UC2843ADR2 Datasheet

UC3842A, 43A UC2842A, 43A

Figure 1. Timing Resistor versus

Oscillator Frequency

 

80

 

 

 

 

 

 

 

 

50

 

 

 

 

 

 

 

(kΩ)

20

 

 

 

 

 

 

 

RESISTOR

 

 

 

 

 

 

 

8.0

 

 

 

 

 

 

 

5.0

 

 

 

 

 

 

 

,TIMING

 

 

 

 

 

 

 

2.0

VCC = 15 V

 

 

 

 

 

T

 

 

 

 

 

R

 

TA = 25°C

 

 

 

 

 

 

 

 

 

 

 

 

 

0.8

10 k

20 k

50 k

100 k

200 k

500 k

1.0 M

 

 

fOSC, OSCILLATOR FREQUENCY (Hz)

Figure 2. Output Deadtime versus

Oscillator Frequency

 

100

 

 

 

 

 

 

DEADTIME

50

VCC = 15 V

 

 

 

 

 

 

TA = 25°C

 

 

 

 

 

 

 

 

 

 

 

 

20

 

 

 

 

 

 

 

OUTPUT

 

 

 

 

 

 

 

10

 

 

 

 

 

 

 

DT, PERCENT

 

 

 

 

 

 

 

5.0

 

 

 

 

 

 

 

2.0

 

 

 

 

 

 

 

%

 

 

 

 

 

 

 

 

 

1.0

10 k

20 k

50 k

100 k

200 k

500 k

1.0 M

 

 

fOSC, OSCILLATOR FREQUENCY (Hz)

I dischg , DISCHARGE CURRENT (mA)

Figure 3. Oscillator Discharge Current

versus Temperature

9.0

VCC = 15 V

VOSC = 2.0 V

8.5

8.0

7.5

7.0

 

 

 

 

 

 

 

±55

±25

0

25

50

75

100

125

TA, AMBIENT TEMPERATURE (°C)

Figure 4. Maximum Output Duty Cycle

versus Timing Resistor

(%)

100

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VCC = 15 V

 

 

 

 

 

 

 

 

 

CYCLE

90

 

 

 

 

 

 

 

 

 

 

 

 

 

TA = 25°C

 

 

 

 

 

 

 

 

 

 

 

 

 

CT = 3.3 nF

 

 

 

 

 

 

 

 

 

DUTY

 

 

 

 

 

 

 

 

 

 

 

 

 

80

 

I

dischg = 7.2 mA

 

 

 

 

 

 

 

 

 

OUTPUT

70

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MAXIMUM,

 

 

 

 

 

 

 

 

 

 

 

 

50

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Idischg

= 9.5 mA

 

 

 

 

 

 

 

max

60

 

 

 

 

 

 

 

 

 

 

 

 

40

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

D

 

 

 

 

 

 

 

 

 

 

 

 

 

800

 

1.0 k

2.0 k

3.0 k 4.0 k

6.0 k 8.0 k

 

 

 

 

 

 

RT, TIMING RESISTOR (Ω)

 

 

 

 

2.55V

2.5V

2.45V

Figure 5. Error Amp Small Signal

Transient Response

VCC = 15 V

AV = ±1.0

TA = 25°C

20 mV/DIV

0.5 μs/DIV

3.0 V

2.5 V

2.0 V

Figure 6. Error Amp Large Signal

Transient Response

VCC = 15 V

AV = ±1.0

TA = 25°C

200 mV/DIV

0.1 μs/DIV

4

MOTOROLA ANALOG IC DEVICE DATA

UC3842A, 43A UC2842A, 43A

Figure 7. Error Amp Open Loop Gain and

Figure 8. Current Sense Input Threshold

Phase versus Frequency

versus Error Amp Output Voltage

(dB)

100

 

 

 

 

 

0

 

(V)

1.2

 

 

 

 

 

 

 

 

VCC = 15 V

 

PHASEEXCESS,φ (DEGREES)

SENSECURRENTINPUT THRESHOLD

 

VCC = 15 V

 

 

 

VOL

 

 

 

 

VO = 2.0 V to 4.0 V

 

 

 

 

 

 

GAIN

80

 

Gain

 

RL = 100 K

30

 

 

1.0

 

 

 

 

VOLTAGE

60

 

 

 

TA = 25°C

60

 

 

0.8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TA = 25°C

 

 

 

LOOP

40

 

 

 

 

 

90

 

 

0.6

TA = 125°C

 

 

 

 

 

 

 

 

Phase

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

, OPEN

20

 

 

 

 

 

120

 

 

0.4

 

TA = ±55°C

 

 

0

 

 

 

 

 

150

 

 

0.2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A

± 20

 

 

 

 

 

180

 

,

 

 

 

 

 

 

 

 

 

 

 

th

0

 

 

 

 

 

10

100

1.0 k

10 k

100 k

1.0 M

10 M

 

V

2.0

4.0

6.0

8.0

 

 

 

0

 

 

 

f, FREQUENCY (Hz)

 

 

 

 

 

VO, ERROR AMP OUTPUT VOLTAGE (V)

 

Figure 9. Reference Voltage Change

versus Source Current

(mV)

0

 

 

 

 

 

 

CHANGE

 

 

 

 

 

VCC = 15 V

 

±4.0

 

 

 

 

 

 

 

 

 

 

 

 

 

VOLTAGE

±8.0

 

 

 

 

 

 

±12

 

 

 

 

 

 

, REFERENCE

 

 

 

 

 

 

±16

 

TA = 125°C

 

TA = 55°C

 

 

 

 

 

 

±20

 

 

TA = 25°C

 

 

 

ref

 

 

 

 

 

 

 

V

±24

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

20

40

60

80

100

120

 

 

Iref, REFERENCE SOURCE CURRENT (mA)

 

 

 

Figure 10. Reference Short Circuit Current

 

(mA)

 

 

versus Temperature

 

 

110

 

 

 

 

 

 

 

CURRENT

 

 

 

 

 

 

 

 

 

 

 

 

 

VCC = 15 V

 

 

 

 

 

 

 

RL 0.1 Ω

 

SHORT CIRCUIT

90

 

 

 

 

 

 

 

70

 

 

 

 

 

 

 

,REFERENCE

 

 

 

 

 

 

 

50

 

 

 

 

 

 

 

SC

 

 

 

 

 

 

 

±55

±25

0

25

50

75

100

125

I

 

 

 

 

TA, AMBIENT TEMPERATURE (°C)

 

OUTPUT, CHANGEVOLTAGE mV/DIV)(2.0

O V

Figure 11. Reference Load Regulation

VCC = 15 V

IO = 1.0 mA to 20 mA

TA = 25°C

2.0 ms/DIV

OUTPUT, CHANGEVOLTAGE mV/DIV)(2.0

O V

Figure 12. Reference Line Regulation

VCC = 12 V to 25 V

TA = 25°C

2.0 ms/DIV

MOTOROLA ANALOG IC DEVICE DATA

5

 

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