Texas Instruments UC2841N, UC2841J, UC2841DWTR, UC1841L883B, UC1841J883B Datasheet

UC1841
UC2841
UC3841

Programmable, Off-Line, PWM Controller

• All Control, Driving, Monitoring, and
Protection Functions Included

• Low-current, Off-line Start Circuit

• Voltage Feed Forward or Current

Mode Control

• Guaranteed Duty Cycle Clamp

• PWM Latch for Single Pulse per Period

• Pulse-by-Pulse Current Limiting Plus

Shutdown for Over-Current Fault

• No Start-up or Shutdown Transients

• Slow Turn-on Both Initially and After

Fault Shutdown

• Shutdown Upon Over- or
Under-Voltage Sensing

• Latch Off or Continuous Retry After
Fault

• PWM Output Switch Usable to 1A
Peak Current

• 1% Reference Accuracy

• 500kHz Operation

• 18 Pin DIL Package

The UC1841 famil y of PWM controllers has been designed to increase
the level of versatility while retaining all of the performance features of
the earlier UC18 40 devices. Wh ile still optimized for highly-efficient boot­strapped pri mary-side operati on in forward or flyback power converters,
the UC1841 is equall y adept in impl ementing b oth low a nd high voltage
input DC to DC converters. Important performance features include a
low-current starting circuit, linear feed-forward for constant volt-second
operation, and compatibility with either voltage or current mode topologies.

In addition to start-up and normal regulating PWM functions, these de­vices include built in protection from over-voltage, under-voltage, and
over-current fault conditions with the option for either latch-of f or automat­ic restart.

While pin compatib le with the UC1840 in all respects except that the po­larity of the External Stop has bee n re versed, the UC1841 offers the fol­lowing improvements:

1. Fault latch reset is accomplished with slow start discharge rather
than recycling the input voltage to the chip.

2. The External Stop input can be used for a fault delay to resist
shutdown from short durat ion transients.

3. The duty-cycle clamping function has been characterized an d
specified.

The UC1841 is characteri zed for -55°C to +125°C operation while the
UC2841 and UC3841 are desi gned for -25°C to +85°C and 0°to +70°C,
respectively.

BLOCK DIAGRAM

Note: Positive tru e logic, latch out put s high with set , reset has prior ity.

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DESCRIPTI ONFEATURES

PARAMETER TEST CONDITIONS

UC1841 / UC2841 UC3841 UNITS

MIN TYP MAX MIN TYP MAX

Power Inputs

Start-Up Curr ent V

IN = 30V, Pin 2 = 2.5V 4.5 6 4.5 6 mA

Operating Cur ren t V

IN = 30V, Pin 2 = 3.5V 10 14 10 14 mA

Supply OV Clamp I

IN = 20mA 33 40 45 33 40 45 V

Reference Sec tio n

Reference Voltage T

J = 25°C 4.95 5.0 5.05 4.9 5.0 5.1 V

Line Regulation V

IN = 8 to 30V 10 15 10 20 mV

Load Regulation I

L = 0 to 10mA 1020 1030mV

Temperature Stability Over Operating Temper ature Range 4.9 5.1 4 .8 5 5.15 V
Short Circuit Current V

REF = 0, TJ

= 25°C -80 -100 -80 -100 mA

Oscillator

Nominal Frequency T

J

= 25°C 47 50 53 45 50 55 kHz

Voltage Stability V

IN = 8 to 30V 0.5 1 0.5 1 %

Temperature Stability Over Operating Temper ature Range 45 55 43 57 kHz
Maximum Frequency R

T = 2kΩ, CT = 330pF 500 500 kHz

UC1841
UC2841
UC3841

ELECTRICAL CHARACTERISTICS:

Unless otherwise stated , these spec ificat ions apply for TA = -55°C to +125°C for the

UC1841, -25°C to +85°C for the UC2841, and 0°C to +70 °C for the UC3841; V

IN = 20V, RT = 20k Ω, CT = .001mfd, RR = 10kΩ,

C

R = .001mfd, Current Limit Th res hold = 200 mV, TA = TJ.

Supply Voltage, +VIN (Pin 15) (Note 2)

Voltage Driven. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +32V

Current Driven, 100mA maximum. . . . . . . . . . . . Self-limiting

PWM Output Volta ge (Pin 12 ) . . . . . . . . . . . . . . . . . . . . . . . 40V

PWM Out put Current, Ste ady-State (Pin 12). . . . . . . . . 400mA

PWM Output Peak Energy Disc harge . . . . . . . . . . . . 20 µJo ules

Driver Bias Current (Pin 14). . . . . . . . . . . . . . . . . . . . . -200mA

Reference Output Current (Pin 16) . . . . . . . . . . . . . . . . -50mA

Slow-Start Sink Curren t (Pin 8) . . . . . . . . . . . . . . . . . . . . 20mA

V

IN Sense Current (Pin 11). . . . . . . . . . . . . . . . . . . . . . . . 10mA

Current Limit Input s (Pins 6 & 7) . . . . . . . . . . . . . -0. 5 to +5.5 V

Stop Input (Pin 4) . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +5.5V

Compara to r Inputs

(Pins 1, 7, 9-1 1, 16). . . . . . . . . . . . Internally clamped at 12V

Power Dissipation at T

A = 25°C (Note 3) . . . . . . . . . . . 1000mW

Power Dissipation at T

C = 25°C (Note 3). . . . . . . . . . . 2000mW

Operating Junct ion Te mp era tu re . . . . . . . . . . -55°C to +150°C

Storage Temperature Ra nge. . . . . . . . . . . . . . -65°C to +150°C

Lead Temp era ture (Solder ing, 10 sec). . . . . . . . . . . . . +300°C

Note 1: All voltages are with respect to ground, Pin 13.

Currents are positiv e-int o, neg at ive-o ut of the specif ie d

terminal.
Note 2: All p in num ber s are refer ence d to DIL- 18 pa ckag e.
Note 3: C on sult Packag in g Section of Dat aboo k for ther ma l

limitations and cons id era tion s of packa ge.

CONNECTION DIAGRAMS

PLCC-20, LCC-20
(TOP VIEW)
Q or L Package

DIL-18, SOIC- 18 (T O P VIEW)
J or N, DW Package

PACKAGE PIN FUNCTIONS

FUNCTION PIN

Comp 1
Start/UV 2
OV Sense 3
Stop 4
Reset 5
CUR Thresh 7
CUR Sense 8
Slow Start 9
R

T/CT 10

Ramp 11
V

IN Sense 12

PWM Out 13
Ground 14
Drive Bias 15
+V

IN Supply 17

5.0V REF 18
Inv. Input 19
N.I. Inpu t 20

ABSOLUTE MAXI MUM RATING S

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PARAMETER TEST CONDITIONS UC1841 / UC2841 UC3841 UNITS

MIN TYP MAX MIN TYP MAX

Ramp Ge nerator

Ramp Curren t, M in imum I

SENSE = -10µA -11 -14 -11 -14 µA

Ramp Current, Maximum I

SENSE = 1.0mA -0.9 -.95 -0.9 -.95 mA

Ramp Valley 0.3 0.4 0.6 0.3 0.4 0.6 V
Ramp Peak Clamp ing Leve l 3.9 4.2 4.5 3.9 4.2 4.5 V

Error Amplifier

Input Offs et Vo lta g e V

CM = 5.0V 0.5 5 2 10 mV

Input Bias Cur ren t 0.5 2 1 5 µA
Input Offs et Cu rr ent 0.5 0.5 µA
Open Loop Gain ∆V

O= 1 to 3V 60 66 60 66 dB

Output Swing (Max. Output ≤
Ramp Peak - 100mV)

Minimum Total Range 0.3 3.5 0.3 3.5 V

CMRR V

CM = 1.5 to 5.5V 70 80 70 80 dB

PSRR V

IN = 8 to 30V 70 80 70 80 dB

Short Circuit Current V

COMP = 0V -4 -10 -4 -10 mA

Gain Bandwidth* T

J = 25°C, AVOL = 0dB 1 2 1 2 MHz

Slew Rate* T

J = 25°C, AVCL

= 0dB 0.8 0.8 V/µs

PWM Section

Continuous Duty Cycle
Range* (other than zero)

Minimum Total Cont inuou s Range,
Ramp Peak < 4.2V

495495%

50% Duty Cycle Clamp R

SENSE to VREF = 10k 42 47 52 42 47 52 %

Output Saturation I

OUT = 20mA 0.2 0.4 0.2 0.4 V

I

OUT = 200mA 1. 7 2.2 1.7 2.2 V

Output Lea kage V

OUT = 40V 0.1 10 0.1 10 µA

Comparator Dela y* Pin 8 to Pin 12, T

J = 25°C, RL = 1kΩ 300 500 300 500 ns

Sequencing Functions

Comparator Thre sholds P ins 2, 3, 5 2.8 3.0 3.2 2.8 3.0 3.2 V
Input Bias Curren t Pins 3, 5 = 0V -1.0 -4.0 -1.0 -4.0 µA
Input Leakage Pins 3, 5 = 10V 0.1 2.0 0.1 2.0 µA
Start/UV Hyster esis Cur ren t Pin 2 = 2.5V 170 200 220 1 70 200 23 0 µA
Ext. Stop Threshold Pin 4 0.8 1.6 2.4 0.8 1.6 2.4 V
Error Latch Activat e Cur ren t P in 4 = 0V, Pin 3 > 3V -120 -200 -120 -200 µA
Driver Bias Saturation Volta ge,

V

IN - VOH

IB = -50mA 2 3 2 3 V

Driver Bias Leakage V

B = 0V -0.1 -10 -0.1 -10 µA

Slow-Start Saturation I

S = 10mA 0.2 0.5 0.2 0.5 V

Slow-Start Leakage V

S = 4.5V 0.1 2.0 0.1 2.0 µA

Current Control

Current Limit Off set 0 5 0 10 mV
Current Shutdown O ffs et 370 400 430 360 400 440 mV
Input Bias Current Pin 7 = 0V -2 -5 -2 -5 µA
Common Mode Ran ge* -0.4 3.0 -0.4 3.0 V
Current Limit Delay* T

J = 25°C, Pin 7 to 12, RL = 1k 200 400 200 400 n s

* These paramet ers are guara nt eed by design bu t not 100% teste d in prod uct ion.

UC1841
UC2841
UC3841

ELECTRICAL CHARACTERISTICS:

Unless otherwise stated , these spec ificat ions apply for TA = -55°C to +125°C for the

UC1841, -25°C to +85°C for the UC2841, and 0°C to +70 °C for the UC3841; V

IN = 20V, RT = 20k Ω, CT = .001mfd, RR = 10kΩ,

C

R = .001mfd, Current Limit Thresh old = 200mV, TA = TJ.

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