Microsemi UC3845AM, UC3845ADM, UC3844AM, UC3844ADM, UC3845AD Datasheet

DESCRIPTION KEY FEATURES

■■

■■

■ LOW START-UP CURRENT. (0.5mA max.)

■■

■■

■ TRIMMED OSCILLATOR DISCHARGE

CURRENT. (See Product Highlight)

p OPTIMIZED FOR OFF-LINE AND DC-TO-DC

CONVERTERS.

p AUTOMATIC FEED FORWARD

COMPENSATION.

p PULSE-BY-PULSE CURRENT LIMITING.
p ENHANCED LOAD RESPONSE

CHARACTERISTICS.

p UNDER-VOLTAGE LOCKOUT WITH

HYSTERESIS.

p DOUBLE PULSE SUPPRESSION.
p HIGH-CURRENT TOTEM POLE OUTPUT.

p INTERNALLY TRIMMED BANDGAP

REFERENCE.

p 500KHz OPERATION.

p LOW R

O

ERROR AMPLIFIER.

The UC184xA family of control ICs
provides all the necessary features to
implement off-line fixed-frequency,
current-mode switching power supplies
with a minimum of external compo­nents. The current mode architecture
demonstrates improved load regulation,
pulse-by-pulse current limiting and
inherent protection of the power supply
output switch. The IC includes: A
bandgap reference trimmed to ±1%
accuracy, an error amplifier, a current
sense comparator with internal clamp to
1V, a high current totem pole output
stage for fast switching of power

MOSFET's, and an externally program­mable oscillator to set frequency and
maximum duty cycle. The under­voltage lock-out is designed to operate
with 250µA typ. start-up current,
allowing an efficient bootstrap supply
voltage design. Available options for
this family of products, such as start-up
voltage hysteresis and duty cycle, are
summarized below in the Available
Options section. The UC184xA family
of control ICs is also available in 14-pin
SOIC package which makes the Power
Output Stage Collector and Ground pins
available.

APPLICATIONS

■■

■■

■ ECONOMICAL OFF-LINE FLYBACK OR

FORWARD CONVERTERS.

■ DC-DC BUCK OR BOOST CONVERTERS.

■ LOW COST DC MOTOR CONTROL.

A VAILABLE OPTIONS

Part # Start-Up Hysteresis Max. Duty

Voltage Cycle

PACKAGE ORDER INFORMATION

T

A

(°C)

Plastic DIP
8-pin

0 to 70 UC384xAM UC384xADM UC384xAD —

-40 to 85 UC284xAM UC284xADM UC284xAD UC284xAY

-55 to 125 — — — UC184xAY

M

Plastic SOIC
8-pin

DM

Plastic SOIC
14-pin

D

Ceramic DIP
8-pin

Y

Note: All surface-mount packages are available in Tape & Reel. Append the letter "T" to part number. (i.e. UC3842ADMT)

UCx842A 16V 6V <100%

UCx843A 8.4V 0.8V <100%

UCx844A 16V 6V <50%

UCx845A 8.4V 0.8V <50%

PRODUCT HIGHLIGHT

COMPARISON OF UC384XA VS. SG384X DISCHARGE CURRENT

UC384xA

7.5 8.3 9.3
Mean

SG384x

Min. Limit

7.8

−3σ

8.8

+3σ

SG384x

Max. Limit

Discharge Current Distribution - mA

T

A

=25°C

C URRENT MODE PWM CONTROLLER

P RODUCTION DATA SHEET

THE INFINITE POWER OF INNOVATION

Copyright © 1995
Rev. 1.2 12/95

FOR FURTHER INFORMATION CALL [phone]

11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841

UC184xA/284xA/384xA

LIN DOC #:

1840

1

C URRENT MODE PWM CONTROLLER

UC184xA/284xA/384xA

PRODUCT DATABOOK 1996/1997

Copyright © 1995

Rev. 1.2 12/95

2

P

RODUCTION DATA SHEET

ABSOLUTE MAXIMUM RATINGS (Note 1)

Supply Voltage (Low Impedance Source) (VCC) ......................................................... 30V

Supply Voltage (I

CC

< 30mA).......................................................................... Self Limiting

Output Current ............................................................................................................. ±1A

Output Energy (Capacitive Load)................................................................................. 5µJ

Analog Inputs (V

FB

& I

SENSE

) ........................................................................ -0.3V to +6.3V

Error Amp Output Sink Current ............................................................................... 10mA

Power Dissipation at T

A

= 25°C (M Package) .............................................................. 1W

Storage Temperature Range .................................................................... -65°C to +150°C

Lead Temperature (Soldering, 10 Seconds) ............................................................. 300°C

PACKAGE PIN OUTS

Note 1. Exceeding these ratings could cause damage to the device. All voltages are with respect

to Ground. Currents are positive into, negative out of the specified terminal. Pin
numbers refer to DIL packages only.

1 8

27

36

45

M & Y PACKAGE

(Top View)

M PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

θθ

θθ

θ

JA

95°C/W

DM PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

θθ

θθ

θ

JA

165°C/W

D PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

θθ

θθ

θ

JA

120°C/W

Y PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

θθ

θθ

θ

JA

130°C/W

Junction Temperature Calculation: T

J

= TA + (P

D

x θ

JA

).

The θ

JA

numbers are guidelines for the thermal performance of the device/pc-board system.

All of the above assume no ambient airflow

THERMAL DATA

DM PACKAGE

(Top View)

V

REF

V

CC

OUTPUT
GND

COMP

V

FB

I

SENSE

RT/C

T

1 8

27

36

45

V

REF

N.C.
V

CC

V

C

OUTPUT
GND
PWR GND

COMP

N.C.

V

FB

N.C.
I

SENSE

N.C.

RT/C

T

1 14

213

312

411

510

69

78

D PACKAGE

(Top View)

COMP

V

FB

I

SENSE

RT/C

T

V

REF

V

CC

OUTPUT
GND

C URRENT MODE PWM CONTROLLER

UC184xA/284xA/384xA

PRODUCT DATABOOK 1996/1997

3

Copyright © 1995
Rev. 1.2 12/95

P RODUCTION DATA SHEET

ELECTRICAL CHARACTERISTICS

(Unless otherwise specified, these specifications apply over the operating ambient temperatures for UC384xA with 0°C ≤ TA ≤ 70°C, UC284xA with -40°C ≤ TA ≤ 85°C,
UC184xA with -55°C ≤ T

A

≤ 125°C; V

CC

=15V; RT=10K; CT=3.3nF. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal

to the ambient temperature.)

Reference Section

Parameter

Symbol

Test Conditions

Output Voltage V

REFTJ

= 25°C, IL = 1mA

Line Regulation 12 ≤ VIN ≤ 25V
Load Regulation 1 ≤ I

O

≤ 20mA

Temperature Stability (Note 2 & 7)
Total Output Variation Over Line, Load, and Temperature
Output Noise Voltage (Note 2) V

N

10Hz ≤ f ≤ 10kHz, TJ = 25°C

Long Term Stability (Note 2) TA = 125°C, t = 1000hrs
Output Short Circuit Current I

SC

UC384xA

Units

Min. Typ. Max. Min. Typ. Max.

UC184xA/284xA

4.95 5.00 5.05 4.90 5.00 5.10 V
620 620 mV
625 625 mV

0.2 0.4 0.2 0.4 mV/°C

4.9 5.1 4.82 5.18 V
50 50 µV

525 525 mV

-30 -100 -180 -30 -100 -180 mA

Oscillator Section

Initial Accuracy (Note 6) TJ = 25°C
Voltage Stability 12 ≤ VCC ≤ 25V
Temperature Stability (Note 2) T

MIN

≤ TA ≤ T

MAX

Amplitude (Note 2)
Discharge Current TJ = 25°C, V

PIN 4

= 2V

V

PIN 4

= 2V, T

MIN

≤ TA ≤ T

MAX

47 52 57 47 52 57 kHz

0.2 1 0.2 1 %
55%

1.7 1.7 V

7.8 8.3 8.8 7.8 8.3 8.8 mA

7.5 8.8 7.6 8.8 mA

Output Low Level

V

OL

I

SINK

= 20mA

I

SINK

= 200mA

Output High Level

V

OH

I

SOURCE

= 20mA

I

SOURCE

= 200mA

Rise Time (Note 2) T

R

TJ = 25°C, CL = 1nF

Fall Time (Note 2) T

F

TJ = 25°C, CL = 1nF

UVLO Saturation V

SATVCC

= 5V, I

SINK

= 10mA

Current Sense Section

Gain (Note 3 & 4) A

VOL

Maximum Input Signal (Note 3) V

PIN 1

= 5V

Power Supply Rejection Ratio (Note 3) PSRR 12 ≤ V

CC

≤ 25V

Input Bias Current I

B

Delay to Output (Note 2) T

pdVPIN 3

= 0 to 2V

Output Section

2.85 3 3.15 2.85 3 3.15 V/V

0.9 1 1.1 0.9 1 1.1 V
70 70 dB

-2 -10 -2 -10 µA

150 300 150 300 ns

0.1 0.4 0.1 0.4 V

1.5 2.2 1.5 2.2 V
13 13.5 13 13.5 V
12 13.5 12 13.5 V

50 150 50 150 ns
50 150 50 150 ns

0.7 1.2 0.7 1.2 V

(Electrical Characteristics continue next page.)

Error Amp Section

Input Voltage V

PIN 1

= 2.5V

Input Bias Current I

B

Open Loop Gain A

VOL

2 ≤ VO ≤ 4V

Unity Gain Bandwidth (Note 2) UGBW T

j

= 25°C

Power Supply Rejection Ratio (Note 3) PSRR 12 ≤ VCC ≤ 25V
Output Sink Current I

OLVPIN 2

= 2.7V, V

PIN 1

= 1.1V

Output Source Current I

OHVPIN 2

= 2.3V, V

PIN 1

= 5V

Output Voltage High Level V

OHVPIN 2

= 2.3V, RL = 15K to ground

Output Voltage Low Level V

OLVPIN 2

= 2.7V, RL = 15K to V

REF

2.45 2.50 2.55 2.42 2.50 2.58 V

-0.3 -1 -0.3 -2 µA

65 90 65 90 dB

0.7 1 0.7 1 MHz
60 70 60 70 dB

26 26 mA

-0.5 -0.8 -0.5 -0.8 mA
56 56 V

0.7 1.1 0.7 1.1 V