Motorola UC3845BVD1, UC3845BVD, UC3845BN, UC3845BD1R2, UC3845BD1 Datasheet

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Order this document by UC3844B/D

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The UC3844B, UC3845B 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 an oscillator, 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, a latch for single pulse metering, and a flip–flop which blanks the output off every other oscillator cycle, allowing output deadtimes to be programmed from 50% to 70%.

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 UCX844B has UVLO thresholds of 16 V (on) and 10 V (off), ideally suited for off–line converters. The UCX845B 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 Output Switching Frequency

• Output Deadtime Adjustable from 50% to 70%

• 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)

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

(Top View)

1 2 3 4 5 6 7

(T op View)

Compensation

Voltage Feedback

Current Sense

Compensation

Voltage Feedback

Current Sense

8 7 6 5

14 13 12 11 10

9 8

ref

Output Gnd

ref

NC V

Output Gnd

Power Ground

5(9)

5.0V

Reference

Latching

ref

RT/C

Voltage

Feedback

Input

Output/

Compensation

8(14)

4(7)

2(3)

1(1)

Error

Amplifier

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

ref

Undervoltage

Lockout

Oscillator

Gnd

MOTOROLA ANALOG IC DEVICE DATA

PWM

Undervoltage

Lockout

7(11)

Output

6(10)

Power Ground

5(8)

Current Sense Input

3(5)

ORDERING INFORMATION

Device

UC384XBD UC384XBD1 UC384XBN Plastic

UC284XBD1 UC284XBN UC384XBVD UC384XBVD1 SO–8 UC384XBVN Plastic

X indicates either a 4 or 5 to define specific device part numbers.

 Motorola, Inc. 1996 Rev 1

Operating

Temperature Range

TA = 0° to + 70°C

TA = – 25° to + 85°C

TA = – 40° to +105°C

Package

SO–14

SO–8

SO–14UC284XBD

SO–8 Plastic SO–14

UC3844B, 45B UC2844B, 45B

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

UC3844B, UC3845B

θJA

UC2844B, UC2845B 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

– 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

Characteristic 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 Total Output V ariation over Line, Load, and Temperature 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

high

to T

low

high

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 UC3844B, UC3845B T

low

=–25°C for UC2844B, UC2845B = + 85°C for UC2844B, UC2845B =–40°C for UC3844BV, UC3845BV = +105°C for UC3844BV, UC3845BV

= 2.0 V)

OSC

(UC284XB, UC384XB) (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 UC3844B, UC3845B

–

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

UC3844B, 45B UC2844B, 45B

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

Characteristic 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

–

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

2.85–3.0–3.15–2.85

2.85

0.9–1.0

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

= 200 mA, UC384XBV)

Sink

= 20 mA, UC284XB, UC384XB)

Source

(I (I

= 20 mA, UC384XBV)

Source

= 200 mA)

Source

= 1.0 mA

Sink

OL(UVLO)

r f

–

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

UCX844B, BV UCX845B, BV

Minimum Operating Voltage After Turn–On

UCX844B, BV UCX845B, 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 UC3844B, UC3845B T

low

=–25°C for UC2844B, UC2845B T

low

=–40°C for UC3844BV, UC3845BV T

low

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

5.Comparator gain is defined as: AV =

V OutputńCompensation

V Current Sense Input

=+70°C for UC3844B, UC3845B

high

=+85°C for UC2844B, UC2845B

high

= +105°C for UC3844BV, UC3845BV

high

CC(min)

7.8168.4

9.0

7.0107.6

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

UC3844B, 45B UC2844B, 45B

ELECTRICAL CHARACTERISTICS

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

Characteristic 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 UCX845B,

Start–Up (VCC 14 V for UCX844B, 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 UC3844B, UC3845B T

low

=–25°C for UC2844B, UC2845B = + 85°C for UC2844B, UC2845B =–40°C for UC3844BV, UC3845BV = +105°C for UC3844BV, UC3845BV

Figure 1. Timing Resistor

versus Oscillator Frequency

80 50

Ω

8.0

5.0

, TIMING RESISTOR (k )

2.0 NOTE: Output switches at 1/2 the oscillator frequency

0.8

, OSCILLAT OR FREQUENCY (kHz)

OSC

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

UC284XB UC384XB, XBV

(max)

(min)

=+70°C for UC3844B, UC3845B

high

30 36 – 30 36 – V

48 – –

–

– –

0.3

Figure 2. Output Deadtime

versus Oscillator Frequency

VCC = 15 V

TA = 25

1.0 M500 k200 k100 k50 k20 k10 k

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

% DT, PERCENT OUTPUT DEADTIME

20 k 50 k 200 k 500 k

OSC

0.5

, OSCILLAT OR FREQUENCY (kHz)

–

48 48

–

0.3

–

50 50

–

0.5

1.0 M100 k10 k

2.55 V

2.5 V

2.45 V

Figure 3. Error Amp Small Signal

Transient Response

VCC = 15 V AV = –1.0 TA = 25

0.5 µs/DIV

Figure 4. Error Amp Large Signal

Transient Response

VCC = 15 V

20 mV/DIV

3.0 V

2.5 V

2.0 V

1.0 µs/DIV

AV = –1.0

TA = 25

200 mV/DIV

MOTOROLA ANALOG IC DEVICE DATA

UC3844B, 45B UC2844B, 45B

Figure 5. Error Amp Open Loop Gain and

100

, OPEN LOOP VOL TAGE GAIN (dB)

VOL

–20

– 4.0

Phase versus Frequency

VCC = 15 V VO = 2.0 V to 4.0 V

Gain

100 1.0 k 10 k 100 k 1.0 M

f, FREQUENCY (Hz)

RL = 100 k

TA = 25

Figure 7. Reference V oltage Change

versus Source Current

VCC = 15 V

Phase

Figure 6. Current Sense Input Threshold

versus Error Amp Output Voltage

120

150

180

10 M10

1.2 VCC = 15 V

1.0

0.8

TA = 25°C

0.6

0.4

, EXCESS PHASE (DEGREES)

0.2

, CURRENT SENSE INPUT THRESHOLD (V)V

TA = 125°C

2.0 4.0 6.0 8.0

VO, ERROR AMP OUTPUT VOLTAGE (VO)

TA = – 55°C

Figure 8. Reference Short Circuit Current

versus T emperature

110

VCC = 15 V

≤

0.1

Ω

– 8.0

–12

–16

–20

, REFERENCE VOLTAGE CHANGE (mV)

ref

∆

–24

20 40 60 80 100 120

ref

Figure 9. Reference Load Regulation Figure 10. Reference Line Regulation

TA = –55°C

TA = 125°C

TA = 25°C

, REFERENCE SOURCE CURRENT (mA)

VCC = 15 V IO = 1.0 mA to 20 mA

TA = 25

, REFERENCE SHORT CIRCUIT CURRENT (mA)

–55

– 25 0 25 50 75 100 125

TA, AMBIENT TEMPERATURE (

VCC = 12 V to 25 V

TA = 25

, OUTPUT VOLTAGE CHANGE (2.0 mV/DIV)

∆

2.0 ms/DIV

MOTOROLA ANALOG IC DEVICE DATA

, OUTPUT VOLTAGE CHANGE (2.0 mV/DIV)

∆

2.0 ms/DIV

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