MOTOROLA UC3842ADR2, UC3842AD, UC2843AN, UC2842AN, UC2843ADR2 Datasheet

Device

Operating

Temperature Range

Package

   

HIGH PERFORMANCE

CURRENT MODE

CONTROLLERS

ORDERING INFORMATION

UC3842AD UC3843AD

TA = 0° to +70°C

TA = – 25° to +85°C

SO–14 SO–14

PIN CONNECTIONS

Order this document by UC3842A/D

D SUFFIX

PLASTIC PACKAGE

CASE 751A

(SO–14)

N SUFFIX

PLASTIC PACKAGE

CASE 626

1

8

1

14

(T op V iew)

V

ref

(T op V iew)

Compensation

Voltage Feedback

Current Sense

RT/C

T

V

ref

V

CC Output Gnd

1 2 3

45

6

7

8

Compensation

NC

Voltage Feedback

NC

Current Sense

NC

RT/C

T

NC V

CC

V

C

Output Gnd Power Ground

1 2 3

4 5 6

7

9 8

10

11

12

13

14

UC3842AN UC3843AN

Plastic

Plastic UC2842AD UC2843AD

SO–14

SO–14 UC2842AN UC2843AN

Plastic

1

MOTOROLA ANALOG IC DEVICE DATA

     

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

5.0V

Reference

Latching

PWM

V

CC

Undervoltage

Lockout

Oscillator

Error

Amplifier

7(12)

V

C

7(11)

Output

6(10)

Power Ground

5(8)

3(5)

Current Sense Input

V

ref

8(14)

4(7)

2(3)

1(1)

Gnd 5(9)

RTC

T

Voltage

Feedback

Input

R

+ –

V

ref

Undervoltage

Lockout

Output

Compensation

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

V

CC

 Motorola, Inc. 1996 Rev 1

UC3842A, 43A UC2842A, 43A

2

MOTOROLA ANALOG IC DEVICE DATA

MAXIMUM RATINGS

Rating Symbol Value Unit

Total Power Supply and Zener Current (ICC + IZ) 30 mA Output Current, Source or Sink (Note 1) I

O

1.0 A Output Energy (Capacitive Load per Cycle) W 5.0 µJ Current Sense and Voltage Feedback Inputs V

in

– 0.3 to + 5.5 V

Error Amp Output Sink Current I

O

10 mA

Power Dissipation and Thermal Characteristics

D Suffix, Plastic Package

Maximum Power Dissipation @ TA = 25°C Thermal Resistance, Junction–to–Air

N Suffix, Plastic Package

Maximum Power Dissipation @ TA = 25°C Thermal Resistance, Junction–to–Air

P

D

R

θJA

P

D

R

θJA

862 145

1.25 100

mW

°C/W

W

°C/W

Operating Junction Temperature T

J

+ 150 °C

Operating Ambient Temperature

UC3842A, UC3843A UC2842A, UC2843A

T

A

0 to + 70

– 25 to + 85

°C

Storage Temperature Range T

stg

– 65 to + 150 °C

ELECTRICAL CHARACTERISTICS (V

CC

= 15 V, [Note 2], RT = 10 k, CT = 3.3 nF, TA = T

low

to T

high

[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) V

ref

4.95 5.0 5.05 4.9 5.0 5.1 V

Line Regulation (VCC = 12 V to 25 V) Reg

line

– 2.0 20 – 2.0 20 mV

Load Regulation (IO = 1.0 mA to 20 mA) Reg

load

– 3.0 25 – 3.0 25 mV

T emperature Stability T

S

– 0.2 – – 0.2 – mV/°C

Total Output V ariation over Line, Load, Temperature V

ref

4.9 – 5.1 4.82 – 5.18 V

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

n

– 50 – – 50 – µV Long Term Stability (TA = 125°C for 1000 Hours) S – 5.0 – – 5.0 – mV Output Short Circuit Current I

SC

– 30 – 85 – 180 – 30 – 85 – 180 mA

OSCILLATOR SECTION

Frequency

TJ = 25°C TA = T

low

to T

high

f

osc

47 46

52

–

57 60

47 46

52

–

57 60

kHz

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

osc/∆V

– 0.2 1.0 – 0.2 1.0 % Frequency Change with Temperature

TA = T

low

to T

high

∆f

osc/∆T

– 5.0 – – 5.0 – %

Oscillator Voltage Swing (Peak–to–Peak) V

osc

– 1.6 – – 1.6 – V Discharge Current (V

osc

= 2.0 V)

TJ = 25°C

TA = T

low

to T

high

I

dischg

7.5

7.2

8.4 –

9.3

9.5

7.5

7.2

8.4 –

9.3

9.5

mA

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 T

low

= –20°C for UC3842A, UC3843A T

high

= +70°C for UC3842A, UC3843A

T

low

= –25°C for UC2842A, UC2843A T

high

= +85°C for UC2842A, UC2843A

UC3842A, 43A UC2842A, 43A

3

MOTOROLA ANALOG IC DEVICE DATA

ELECTRICAL CHARACTERISTICS (V

CC

= 15 V, [Note 2], RT = 10 k, CT = 3.3 nF, TA = T

low

to T

high

[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) V

FB

2.45 2.5 2.55 2.42 2.5 2.58 V

Input Bias Current (VFB = 2.7 V) I

IB

– –0.1 –1.0 – –0.1 –2.0 µA

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

VOL

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

Sink (VO = 1.1 V , VFB = 2.7 V) Source (VO = 5.0 V , VFB = 2.3 V)

I

Sink

I

Source

2.0

–0.512–1.0

– –

2.0

–0.512–1.0

– –

mA

Output Voltage Swing

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

ref

, VFB = 2.7 V)

V

OH

V

OL

5.0 –

6.2

0.8

–

1.1

5.0 –

6.2

0.8

–

1.1

V

CURRENT SENSE SECTION

Current Sense Input Voltage Gain (Notes 4 & 5) A

V

2.85 3.0 3.15 2.85 3.0 3.15 V/V

Maximum Current Sense Input Threshold (Note 4) V

th

0.9 1.0 1.1 0.9 1.0 1.1 V

Power Supply Rejection Ratio

VCC = 12 to 25 V (Note 4)

PSRR

– 70 – – 70 –

dB

Input Bias Current I

IB

– –2.0 –10 – –2.0 –10 µA

Propagation Delay (Current Sense Input to Output) t

PLH(in/out)

– 150 300 – 150 300 ns

OUTPUT SECTION

Output Voltage

Low State (I

Sink

= 20 mA)

Low State (I

Sink

= 200 mA)

High State (I

Sink

= 20 mA)

High State (I

Sink

= 200 mA)

V

OL

V

OH

–

– 13 12

0.1

1.6

13.5

13.4

0.4

2.2 – –

–

– 13 12

0.1

1.6

13.5

13.4

0.4

2.2 – –

V

Output Voltage with UVLO Activated

VCC = 6.0 V , I

Sink

= 1.0 mA

V

OL(UVLO)

– 0.1 1.1 – 0.1 1.1

V

Output Voltage Rise T ime (CL = 1.0 nF, TJ = 25°C) t

r

– 50 150 – 50 150 ns

Output Voltage Fall T ime (CL = 1.0 nF, TJ = 25°C) t

f

– 50 150 – 50 150 ns

UNDERVOLTAGE LOCKOUT SECTION

Startup Threshold

UCX842A UCX843A

V

th

15

7.8

16

8.4

17

9.0

14.5

7.8

16

8.4

17.5

9.0

V

Minimum Operating Voltage After Turn–On

UCX842A UCX843A

V

CC(min)

9.0

7.0

10

7.6

11

8.2

8.5

7.0

10

7.6

11.5

8.2

V

PWM SECTION

Duty Cycle

Maximum Minimum

DC

max

DC

min

94

–

96

–

– 0

94

–

96

–

– 0

%

TOTAL DEVICE

Power Supply Current (Note 2)

Startup: (VCC = 6.5 V for UCX843A,

(VCC = 14 V for UCX842A) Operating

I

CC

– –

0.5 12

1.0 17

– –

0.5 12

1.0 17

mA

Power Supply Zener Voltage (ICC = 25 mA) V

Z

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 T

low

= –20°C for UC3842A, UC3843A T

high

= +70°C for UC3842A, UC3843A

T

low

= –25°C for UC2842A, UC2843A T

high

= +85°C for UC2842A, UC2843A

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

5.Comparator gain is defined as: A

V

∆V Output Compensation

∆V Current Sense Input

UC3842A, 43A UC2842A, 43A

4

MOTOROLA ANALOG IC DEVICE DATA

R

T

Ω

, TIMING RESISTOR (k )

Figure 1. Timing Resistor versus

Oscillator Frequency

Figure 2. Output Deadtime versus

Oscillator Frequency

Figure 3. Oscillator Discharge Current

versus Temperature

Figure 4. Maximum Output Duty Cycle

versus Timing Resistor

Figure 5. Error Amp Small Signal

Transient Response

Figure 6. Error Amp Large Signal

Transient Response

0.5 µs/DIV

20 mV/DIV

VCC = 15 V

AV = –1.0 TA = 25

°

C

10 k 20 k 50 k 100 k 200 k 500 k 1.0 M

f

OSC

, OSCILLATOR FREQUENCY (Hz)

VCC = 15 V

TA = 25

°

C

10 k 20 k 50 k 100 k 200 k 500 k 1.0 M

f

OSC

, OSCILLATOR FREQUENCY (Hz)

% DT, PERCENT OUTPUT DEADTIME

VCC = 15 V

TA = 25

°

C

–55 –25 0 25 50 75 100 125

TA, AMBIENT TEMPERATURE (

°

C)

, DISCHARGE CURRENT (mA)

dischg

I

VCC = 15 V V

OSC

= 2.0 V

RT, TIMING RESISTOR (Ω)

800 1.0 k 2.0 k 3.0 k 4.0 k 6.0 k 8.0 k

, MAXIMUM OUTPUT DUTY CYCLE (%)

max

D

VCC = 15 V CT = 3.3 nF

TA = 25

°

C

I

dischg

= 9.5 mA

I

dischg

= 7.2 mA

2.55 V

2.5 V

2.45 V

VCC = 15 V

AV = –1.0

TA = 25

°

C

0.1 µs/DIV

200 mV/DIV

2.5 V

3.0 V

2.0 V

80 50

20

8.0

5.0

2.0

0.8

100

50

20

10

5.0

2.0

1.0

9.0

8.5

8.0

7.5

7.0

100

90

80

70

60

50

40

UC3842A, 43A UC2842A, 43A

5

MOTOROLA ANALOG IC DEVICE DATA

Figure 7. Error Amp Open Loop Gain and

Phase versus Frequency

Figure 8. Current Sense Input Threshold

versus Error Amp Output Voltage

Figure 9. Reference Voltage Change

versus Source Current

Figure 10. Reference Short Circuit Current

versus Temperature

Figure 11. Reference Load Regulation

Figure 12. Reference Line Regulation

∆

, OUTPUT VOLTAGE CHANGE (2.0 mV/DIV)

O

2.0 ms/DIV

V

∆

, OUTPUT VOLTAGE CHANGE (2.0 mV/DIV)

O

2.0 ms/DIV

V

VCC = 12 V to 25 V TA = 25

°

C

∆

, REFERENCE VOLTAGE CHANGE (mV)

ref

0 20 40 60 80 100 120

I

ref

, REFERENCE SOURCE CURRENT (mA)

V

VCC = 15 V

TA = 55°C

TA = 125°C

, REFERENCE SHORT CIRCUIT CURRENT (mA)

SC

–55 –25 0 25 50 75 100 125

TA, AMBIENT TEMPERATURE (

°

C)

VCC = 15 V

RL

≤

0.1

Ω

I

VCC = 15 V

IO = 1.0 mA to 20 mA

TA = 25

°

C

0

–4.0

–8.0

–12

–16

–20

–24

110

90

70

50

TA = 25°C

–20

A

VOL

, OPEN LOOP VOL TAGE GAIN (dB)

10 M10

f, FREQUENCY (Hz)

Gain

Phase

VCC = 15 V

VO = 2.0 V to 4.0 V

RL = 100 K TA = 25

°

C

0

30

60

90

120

150 180

100 1.0 k 10 k 100 k 1.0 M

0

20

40

60

80

100

, EXCESS PHASE (DEGREES)

φ

0

VO, ERROR AMP OUTPUT VOLTAGE (V)

0

, CURRENT SENSE INPUT THRESHOLD (V) V

th

0.2

0.4

0.6

0.8

1.0

1.2

2.0 4.0 6.0 8.0

VCC = 15 V

TA = 25°C

TA = –55°C

TA = 125°C