Motorola UC3843BVD, UC3843BN, UC3843BD1R2, UC3843BD1, UC3843BD Datasheet

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The UC3842B, UC3843B series are high performance fixed frequency current mode controllers. They 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 and surface mount (SO–8) 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 UCX842B has UVLO thresholds of 16 V (on) and 10 V (off), ideally suited for off–line converters. The UCX843B is tailored for lower voltage applications having UVLO thresholds of 8.5 V (on) and 7.6 V (off).

• Trimmed Oscillator for Precise Frequency Control

• Oscillator Frequency Guaranteed at 250 kHz

• 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

Simplified Block Diagram

7(12)

ref

8(14)

RT/C

4(7)

Voltage

Feedback

Input

2(3)

Output

Compensation

1(1)

5.0V

Oscillator

+ –

Error

Amplifier

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

Undervoltage

Lockout

Gnd 5(9)

Reference

ref

Latching

PWM

Undervoltage

Lockout

7(11)

Output

6(10)

Power Ground

5(8)

3(5)

Current Sense Input

Order this document by UC3842B/D

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HIGH PERFORMANCE

CURRENT MODE

CONTROLLERS

N SUFFIX

PLASTIC PACKAGE

CASE 626

D1 SUFFIX

PLASTIC PACKAGE

CASE 751

(SO–8)

D SUFFIX

PLASTIC PACKAGE

CASE 751A

(SO–14)

PIN CONNECTIONS

RT/C

1 2 3 4

1 2 3 4 5 6 7

Compensation

Voltage Feedback

Current Sense

Compensation

Voltage Feedback

Current Sense

ORDERING INFORMATION

Device

UC384XBD UC384XBD1 TA = 0° to +70°C UC384XBN UC284XBD UC284XBD1 UC284XBN UC384XBVD UC384XBVD1 UC384XBVN

X indicates either a 2 or 3 to define specific device part numbers.

Operating

Temperature Range

TA = – 25° to +85°C

TA = –40° to +105°C

(Top View)

ref

Output

Gnd

ref

Output

Gnd

Power Ground

Package

SO–14

SO–8 Plastic SO–14

SO–8 Plastic

MOTOROLA ANALOG IC DEVICE DATA

 Motorola, Inc. 1996 Rev 1

UC3842B, 43B UC2842B, 43B

MAXIMUM RATINGS

Rating Symbol Value Unit

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

Output Energy (Capacitive Load per Cycle) W 5.0 µJ Current Sense and Voltage Feedback Inputs V Error Amp Output Sink Current I

Power Dissipation and Thermal Characteristics

D Suffix, Plastic Package, SO–14 Case 751A

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

D1 Suffix, Plastic Package, SO–8 Case 751

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

N Suffix, Plastic Package, Case 626

Maximum Power Dissipation @ TA = 25°C

Thermal Resistance, Junction–to–Air Operating Junction Temperature T Operating Ambient Temperature

UC3842B, UC3843B

θJA

UC2842B, UC2843B UC3842BV, UC3843BV

Storage Temperature Range T

stg

1.0 A

– 0.3 to + 5.5 V

10 mA

862 145

702 178

1.25 100

+150 °C

0 to + 70 – 25 to + 85 –40 to +105

– 65 to +150 °C

°C/W

°C

ELECTRICAL CHARACTERISTICS (V

= 15 V [Note 2], RT = 10 k, CT = 3.3 nF . For typical values TA = 25°C, for min/max values TA is

the operating ambient temperature range that applies [Note 3], unless otherwise noted.)

UC284XB UC384XB, XBV

Characteristics Symbol Min Typ Max Min Typ Max Unit

REFERENCE SECTION

Reference Output Voltage (IO = 1.0 mA, TJ = 25°C) V Line Regulation (VCC = 12 V to 25 V) Reg Load Regulation (IO = 1.0 mA to 20 mA) Reg T emperature Stability T T otal Output V ariation over Line, Load, and T emperature V Output Noise Voltage (f = 10 Hz to 10 kHz, TJ = 25°C) V

ref

line load S

ref

4.95 5.0 5.05 4.9 5.0 5.1 V – 2.0 20 – 2.0 20 mV – 3.0 25 – 3.0 25 mV – 0.2 – – 0.2 – mV/°C

4.9 – 5.1 4.82 – 5.18 V – 50 – – 50 – µV

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

–30 –85 –180 –30 –85 –180 mA

OSCILLATOR SECTION

Frequency

TJ = 25°C TA = T TJ = 25°C (RT = 6.2 k, CT = 1.0 nF)

low

to T

high

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

TA = T

low

to T

high

Oscillator Voltage Swing (Peak–to–Peak) V Discharge Current (V

TJ = 25°C TA = T

TA = T

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

to T

low

to T

low

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

=0°C for UC3842B, UC3843B T

low

= –25°C for UC2842B, UC2843B T

low

= –40°C for UC3842BV , UC3843BV T

low

= 2.0 V)

OSC

(UC284XB, UC384XB)

high

(UC384XBV)

high

OSC

49 48

225

/∆V – 0.2 1.0 – 0.2 1.0 %

OSC

∆f

/∆T – 1.0 – – 0.5 – %

OSC

dischg

– 1.6 – – 1.6 – V

7.8

7.5 –

= +70°C for UC3842B, UC3843B

high

= +85°C for UC2842B, UC2843B

high

= +105°C for UC3842BV , UC3843BV

high

–

250

8.3 – –

55 56

275

8.8

8.8 –

49 48

225

7.8

7.6

7.2

–

250

8.3 – –

55 56

275

8.8

kHz

MOTOROLA ANALOG IC DEVICE DATA

UC3842B, 43B UC2842B, 43B

ELECTRICAL CHARACTERISTICS (V

= 15 V [Note 2], RT = 10 k, CT = 3.3 nF . For typical values TA = 25°C, for min/max values TA is

the operating ambient temperature range that applies [Note 3], unless otherwise noted.)

UC284XB UC384XB, XBV

Characteristics Symbol Min Typ Max Min Typ Max Unit

ERROR AMPLIFIER SECTION

Voltage Feedback Input (VO = 2.5 V) V Input Bias Current (VFB = 5.0 V) I Open Loop Voltage Gain (VO = 2.0 V to 4.0 V) A

VOL

2.45 2.5 2.55 2.42 2.5 2.58 V – – 0.1 –1.0 – – 0.1 – 2.0 µA

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)

Sink

Source

2.0

– 0.512–1.0

– –

2.0

– 0.512–1.0

– –

Output Voltage Swing

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

(UC284XB, UC384XB)

, VFB = 2.7 V)

ref

(UC384XBV)

5.0

6.2

– –

0.8 –

1.1

–

5.0

6.2

– –

0.8

–

1.1

1.2

CURRENT SENSE SECTION

Current Sense Input Voltage Gain (Notes 4 & 5)

(UC284XB, UC384XB) (UC384XBV)

Maximum Current Sense Input Threshold (Note 4)

(UC284XB, UC384XB) (UC384XBV)

Power Supply Rejection Ratio

2.85 –

0.9 –

3.0

1.0

–

3.15–2.85

2.85

1.1 –

0.9

0.85

3.0

1.0

3.15

3.25

1.1

PSRR – 70 – – 70 – dB

VCC = 12 V to 25 V, Note 4 Input Bias Current I Propagation Delay (Current Sense Input to Output) t

PLH(In/Out)

– – 2.0 –10 – – 2.0 –10 µA – 150 300 – 150 300 ns

OUTPUT SECTION

Output Voltage

Low State (I

High State (I

Output Voltage with UVLO Activated

VCC = 6.0 V, I Output Voltage Rise T ime (CL = 1.0 nF, TJ = 25°C) t Output Voltage Fall T ime (CL = 1.0 nF, TJ = 25°C) t

= 20 mA)

Sink

= 200 mA) (UC284XB, UC384XB)

Sink

Source

= 20 mA) (UC284XB, UC384XB)

= 200 mA)

= 1.0 mA

Sink

(UC384XBV)

OL(UVLO)

– – –

–

0.1

1.6 –

13.5 –

13.4

0.4

2.2

–

– – – – –

–

12.9 12

0.1

1.6

13.5

13.4

0.4

2.2

2.3 – – –

– 0.1 1.1 – 0.1 1.1 V

– 50 150 – 50 150 ns – 50 150 – 50 150 ns

UNDERVOLTAGE LOCKOUT SECTION

Startup Threshold (VCC)

UCX842B, BV UCX843B, BV

Minimum Operating Voltage After Turn–On (VCC)

UCX842B, BV UCX843B, BV

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

=0°C for UC3842B, UC3843B T

low

= –25°C for UC2842B, UC2843B T

low

= –40°C for UC3842BV , UC3843BV T

low

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

5.Comparator gain is defined as: A

∆V Output Compensation

∆V Current Sense Input

7.8

CC(min)

9.0

7.0

= +70°C for UC3842B, UC3843B

high

= +85°C for UC2842B, UC2843B

high

= +105°C for UC3842BV , UC3843BV

high

8.4

7.6

9.0

8.2

14.5

7.8

8.5

7.0

8.4

7.6

17.5

9.0

11.5

8.2

V/V

MOTOROLA ANALOG IC DEVICE DATA

UC3842B, 43B UC2842B, 43B

ELECTRICAL CHARACTERISTICS

is the operating ambient temperature range that applies [Note 3], unless otherwise noted.)

Characteristics Symbol Min Typ Max Min Typ Max Unit

PWM SECTION

Duty Cycle

Maximum (UC284XB, UC384XB)

Maximum (UC384XBV)

Minimum

TOTAL DEVICE

Power Supply Current

Startup (VCC = 6.5 V for UCX843B,

Startup (VCC 14 V for UCX842B, BV)

Operating (Note 2)

Power Supply Zener Voltage (ICC = 25 mA) 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

=0°C for UC3842B, UC3843B T

low

= –25°C for UC2842B, UC2843B T

low

= –40°C for UC3842BV , UC3843BV T

low

= 15 V [Note 2], RT = 10 k, CT = 3.3 nF, for typical values TA = 25°C, for min/max values T

UC284XB UC384XB, BV

(max)

(min)

ICC + I

= +70°C for UC3842B, UC3843B

high

= +85°C for UC2842B, UC2843B

high

= +105°C for UC3842BV , UC3843BV

high

– –

–

30 36 – 30 36 – V

– –

0.3

0.5

– – 0

94 93

–

0.3

– – 0

0.5

80 50

Ω

8.0

5.0

, TIMING RESISTOR (k )

2.0

0.8

9.0

8.5

Figure 1. Timing Resistor

versus Oscillator Frequency

VCC = 15 V

TA = 25

, OSCILLAT OR FREQUENCY (kHz)

OSC

Figure 3. Oscillator Discharge Current

versus T emperature

VCC = 15 V V

= 2.0 V

OSC

Figure 2. Output Deadtime

versus Oscillator Frequency

100

1. CT = 10 nF

2. CT = 5.0 nF

3. CT = 2.0 nF

4. CT = 1.0 nF

5. CT = 500 pF

6. CT = 200 pF

7. CT = 100 pF

5.0

2.0

% DT, PERCENT OUTPUT DEADTIME

1.0 M500 k200 k100 k50 k20 k10 k

1.0 f

, OSCILLAT OR FREQUENCY (kHz)

OSC

VCC = 15 V

TA = 25

1.0 M500 k200 k100 k50 k20 k10 k

Figure 4. Maximum Output Duty Cycle

versus Timing Resistor

100

dischg

= 7.5 mA

8.0

, DISCHARGE CURRENT (mA)

7.5

dischg

7.0 –55

– 25 0 25 50 75 100 125

TA, AMBIENT TEMPERATURE (

, MAXIMUM OUTPUT DUTY CYCLE (%)

max

0.8

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0

= 8.8 mA

dischg

RT, TIMING RESISTOR (k

VCC = 15 V CT = 3.3 nF TA = 25

Ω

)

MOTOROLA ANALOG IC DEVICE DATA

UC3842B, 43B UC2842B, 43B

2.55 V

2.50 V

2.45 V

100

Figure 5. Error Amp Small Signal

Transient Response

VCC = 15 V AV = –1.0

TA = 25

Figure 7. Error Amp Open Loop Gain and

Phase versus Frequency

VCC = 15 V VO = 2.0 V to 4.0 V

Gain

RL = 100 K

TA = 25

20 mV/DIV

3.0 V

2.5 V

2.0 V

1.2

1.0

0.8

Figure 6. Error Amp Large Signal

Transient Response

VCC = 15 V AV = –1.0 TA = 25

1.0 µs/DIV0.5 µs/DIV

Figure 8. Current Sense Input Threshold

versus Error Amp Output Voltage

VCC = 15 V

TA = 25°C

, OPEN LOOP VOL TAGE GAIN (dB)

VOL

–20

100 1.0 k 10 k 100 k 1.0 M

Figure 9. Reference V oltage Change

– 4.0

– 8.0

–12

TA = 125°C

–16

–20

, REFERENCE VOLTAGE CHANGE (mV)

ref

∆

–24

20 40 60 80 100 120

, REFERENCE SOURCE CURRENT (mA)

ref

f, FREQUENCY (Hz)

versus Source Current

TA = 25°C

Phase

VCC = 15 V

TA = –55°C

120

, EXCESS PHASE (DEGREES)

150 180

10 M10

0.6

0.4

0.2

, CURRENT SENSE INPUT THRESHOLD (V)

110

, REFERENCE SHORT CIRCUIT CURRENT (mA)

–55

TA = 125°C

TA = –55°C

2.0 4.0 6.0 8.0

VO, ERROR AMP OUTPUT VOLTAGE (V)

Figure 10. Reference Short Circuit Current

versus T emperature

VCC = 15 V

≤

0.1

Ω

– 25 0 25 50 75 100 125

TA, AMBIENT TEMPERATURE (

MOTOROLA ANALOG IC DEVICE DATA

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