Philips uc3842 DATASHEETS

Philips Semiconductors Linear Products Product specification

UC3842Current-mode PWM controller

1100

August 31, 1994 853-0614 13721

DESCRIPTION

The UC3842 is available in an 8-Pin mini-DIP the necessary
features to implement off-line, fixed-frequency current-mode control
schemes with a minimal external parts count. This technique results
in improved line regulation, enhanced load response characteristics,
and a simpler, easier to design control loop. Topological advantages
include inherent pulse-by-pulse current limiting.

Protection circuitry includes built-in undervoltage lock-out and
current limiting. Other features include fully-latched operation, a 1%
trimmed bandgap reference, and start-up current less than 1mA.

These devices feature a totem-pole output designed to source and
sink high peak current from a capacitive load, such as the gate of a
power MOSFET. Consistent with N-channel power devices, the
output is low in the OFF-state.

FEATURES

•Low start-up current (≤1mA)

•Automatic feed-forward compensation

•Pulse-by-pulse current limiting

•Enhanced load response characteristics

•Undervoltage lock-out with hysteresis

•Double pulse suppression

•High current totem-pole output

•Internally-trimmed bandgap reference

•400kHz operation, guaranteed min

PIN CONFIGURATIONS

N Package

D Package

1

2

3

4 5

6

7

8

1
2
3
4
5
6
7 8

14
13
12
11
10

9

COMP

NC

COMP

V

FB

I

SENSE

RT/C

T

V

FB

I

SENSE

RT/C

T

NC

NC

V

REF

V

CC

OUTPUT

GROUND

NC

V

REF

V

CC

OUTPUT
GROUND

V

C

POWER GROUND

TOP VIEW

TOP VIEW

APPLICATIONS

•Off-line switched mode power supplies

•DC-to-DC converters UC3842

BLOCK DIAGRAM

NOTE:

Pin numbers in parentheses refer to the D package.

(12)7

(9)5

(7)4

(3)2

(1)1

(5)3

7(11)

8(14)

6(10)

5(8)

GND

COMP

CURRENT

SENSE

CURRENT
SENSE
COMPARATOR

PWM
LATCH

INTERNAL
BIAS

5V
REF

UVLO

34V

16V

OSC

ERROR
AMP

+
–

2R

R

1V

2.5V

5.0V
50mA

OUTPUT

6V

V

REF

V

CC

V

FB

S/R

RT/C

T

S

R

Philips Semiconductors Linear Products Product specification

UC3842Current-mode PWM controller

August 31, 1994

1101

ORDERING INFORMATION

DESCRIPTION TEMPERATURE RANGE ORDER CODE DWG #

8-Pin Plastic Dual In-Line Package (DIP) 0 to +70°C UC3842N 0404B
14-Pin Plastic Small Outline (SO) Package 0 to +70°C UC3842D 0405B

ABSOLUTE MAXIMUM RATINGS

1

SYMBOL

PARAMETER RATING UNIT

V

CC

Supply voltage (ICC<30mA) Self-Limiting

V

CC

Supply voltage
(low impedance source)

30 V

I

OUT

Output current

2, 3

±1 A
Output energy (capacitive load) 5 µJ
Analog inputs (Pin 2, Pin 3) -0.3 to 6.3 V
Error amp output sink current 10 mA

P

D

Power dissipation at TA≤70°C 1 W
(derate 12.5mW/°C for TA>70°C)

2

T

STG

Storage temperature range -65 to +150 °C

T

SOLD

Lead temperature
(soldering, 10sec max)

300 °C

NOTES:

1. All voltages are with respect to Pin 5; all currents are positive into the specified terminal.

2. See section in application note on “Power Dissipation Calculation”.

3. This parameter is guaranteed, but not 100% tested in production.

Philips Semiconductors Linear Products Product specification

UC3842Current-mode PWM controller

August 31, 1994

1102

DC AND AC ELECTRICAL CHARACTERISTICS

0≤TJ≤70°C for UC3842; VCC=15V; RT=10kW; CT=3.3nF, unless otherwise specified.

UC3842

SYMBOL

PARAMETER

TEST CONDITIONS

Min Typ Max

UNIT

Reference section

V

OUT

Output voltage TJ=25°C, IO=1mA 4.90 5.00 5.10 V
Line regulation 12≤VIN≤25V 6 20 mV
Load regulation 1≤IO≤20mA 6 25 mV
Temp. stability

1

0.2 0.4 mV/°C

Total output variation

1

Line, load, temp. 4.82 5.18 V

V

NOISE

Output noise voltage

1

10Hz≤f≤10kHz, TJ=25°C 50 µV

Long-term stability

1

TJ=125°C, 1000 Hrs. 5 25 mV
Output short-circuit TJ=25 -30 -100 -130 mA
Output short-circuit -55<TJ≤0°C -30 -100 -180 mA

Oscillator section

Initial accuracy TJ=25°C 47 52 57 kHz
Voltage stability 12≤VCC≤25V 0.2 1 %
Temp. stability

1

T

MIN≤TJ≤TMAX

5 %

Amplitude V

PIN 4

peak-to-peak 1.7 V

Error amp section

Input voltage V Pin 1=2.5V 2.42 2.50 2.58 V

I

BIAS

Input bias current -0.3 -2 µA

A

VOL

2≤VO≤4V 65 90 dB

Unity gain bandwidth

1

TJ=25°C 0.7 1 MHz

Unity gain bandwidth T

MIN<TJ<TMAX

0.5 MHz
PSRR Power supply rejection ratio 12≤VCC≤25V 60 70 dB
I

SINK

Output sink current V

PIN 2

=2.7V, V

PIN 1

=1.1V 2 6 mA

I

SOURCE

Output source current V

PIN 2

=2.3V, V

PIN 1

=5V -0.5 -0.8 mA

V

OUT

High V

PIN 2

=2.3V, RL=15k to ground 5 6 V

V

OUT

Low V

PIN 2

=2.7V, RL=15k to Pin 8 0.7 1.1 V

Current sense section

Gain

2, 3

2.85 3 3.15 V/V

Maximum input signal

2

V

PIN 1

=5V 0.9 1 1.1 V

PSRR Power supply rejection ratio

2

12≤VCC≤25V 70 dB

I

BIAS

Input bias current -2 -10 µA
Delay to output

1

150 300 ns