The UC1842/3/4/5 family of control ICs provides the necessary features to
implement off-line or DC to DC fixed frequency current mode control schemes
with a minimal external parts count. Internally implemented circuits include
under-voltage lockout featuring start up current less than 1mA, a precision
reference trimmed for accuracy at the error amp input, logic to insure latched
operation, a PWM comparator which also provides current limit control, and a
totem pole output stage designed to source or sink high peak current. The
output stage, suitable for driving N Channel MOSFETs, is low in the off state.
Differences between members of this family are the under-voltage lockout
thresholds and maximum duty cycle ranges. The UC1842 and UC1844 have
UVLO thresholds of 16V (on) and 10V (off), ideally suited to off-line
applications. The corresponding thresholds for the UC1843 and UC1845 are
8.4V and 7.6V. The UC1842 and UC1843 can operate to duty cycles
approaching 100%. A range of zero to 50% is obtained by the UC1844 and
UC1845 by the addition of an internal toggle flip flop which blanks the output
off every other clock cycle.
BLOCK DIAGRAM
Note 1:A = DIL-8 Pin Number. B = SO-14 and CFP-14 Pin Number.
Note 2:Toggle flip flop used only in 1844 and 1845.
A/B
SLUS223A - APRIL1997 - REVISED MAY 2002
ABSOLUTE MAXIMUM RATINGS(Note 1)
Supply Voltage (Low Impedance Source)..............30V
Unless otherwise stated, these specifications apply for -55°C≤TA≤125°C for the
UC184X; -40°C≤T
(Note 5); R
T = 10k; CT = 3.3nF, TA=TJ.
85°C for the UC284X; 0°C≤T
A
≤
UC1842/3/4/5
70°C for the 384X; V
A
≤
UC3842/3/4/5UNITS
UC2842/3/4/5
MINTYPMAXMINTYPMAX
Reference Section
Output VoltageT
Line Regulation12≤V
Load Regulation1≤I
J = 25°C, IO = 1mA4.955.005.054.905.005.10V
IN
25V620620mV
≤
0
20mA625625mV
≤
Temp. Stability(Note 2) (Note 7)0.20.40.20.4mV/°C
Total Output VariationLine, Load, Temp. (Note 2)4.95.14.825.18V
Output Noise Voltage10Hz≤f≤10kHz, T
Long Term StabilityT
A = 125°C, 1000Hrs. (Note 2)525525mV
J = 25°C (Note2)5050
Output Short Circuit-30-100-180-30-100-180mA
Oscillator Section
Initial AccuracyT
Voltage Stability12≤V
Temp. StabilityT
AmplitudeV
J = 25°C (Note 6)475257475257kHz
CC
25V0.210.21%
≤
T
MIN
PIN 4 peak to peak (Note 2)1.71.7V
T
A
≤
MAX (Note 2)55%
≤
Error Amp Section
Input VoltageV
PIN 1 = 2.5V2.452.502.552.422.502.58V
Input Bias Current-0.3-1-0.3-2
A
VOL2
Unity Gain Bandwidth(Note 2) T
PSRR12≤V
Output Sink CurrentV
Output Source CurrentV
V
OUT HighVPIN 2 = 2.3V, RL = 15k to ground5656V
V
OUT LowVPIN 2 = 2.7V, RL = 15k to Pin 80.71.10.71.1V
Start-Up Current0.510.51mA
Operating Supply CurrentV
V
CC Zener VoltageICC = 25mA30343034V
PIN 2 =VPIN 3 =0V11171117mA
Note 2:These parameters, although guaranteed, are not 100% tested in production.
Note 3:Parameter measured at trip point of latch with V
PIN 2 =0
.
Note 4:Gain defined as:
Note 5:Adjust V
CC above the start threshold before setting at 15V.
∆
A
∆
VPIN
1
VPINV=≤≤
0308;.
3
.
VPIN
Note 6:Output frequency equals oscillator frequency for the UC1842 and UC1843.
Output frequency is one half oscillator frequency for the UC1844 and UC1845.
ERROR AMP CONFIGURATION
Error Amp can Source or Sink up to 0.5mA
4
UNDER-VOLTAGE LOCKOUT
UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5
During under-voltage lock-out, the output driver is
biased to sink minor amounts of current. Pin 6 should
be shunted to ground with a bleeder resistor to prevent
CURRENT SENSE CIRCUIT
Peak Current (IS) is Determined By The Formula
SMAX ′
I
A small RC filter may be required to suppress switch transients
OSCILLATOR SECTION
activating the power switch with extraneous leakage
currents.
1.0V
RS
.
5
OUTPUT SATURATION CHARACTERISTICS
OPEN-LOOP LABORATORY FIXTURE
UC1842/3/4/5
UC2842/3/4/5
ERROR AMPLIFIER OPEN-LOOP
FREQUENCY RESPONSE
High peak currents associated with capacitive loads ne
cessitate careful grounding techniques. Timing and by
pass capacitors should be connected close to pin 5 in a
SHUT DOWN TECHNIQUES
Shutdown of the UC1842 can be accomplished by two
methods; either raise pin 3 above 1V or pull pin 1 below
a voltage two diode drops above ground. Either method
causes the output of the PWM comparator to be high
(refer to block diagram). The PWM latch is reset domi
nant so that the output will remain low until the next
-
single point ground. The transistor and 5k potentiometer
-
are used to sample the oscillator waveform and apply
an adjustable ramp to pin 3.
clock cycle after the shutdown condition at pin 1 and/or
3 is removed. In one example, an externally latched
shutdown may be accomplished by adding an SCR
which will be reset by cycling V
-
UVLO threshold. At this point the reference turns off, al
lowing the SCR to reset.
CC below the lower
-
6
OFFLINE FLYBACK REGULATOR
UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5
Power Supply Specifications
1. Input Voltages5VAC to 130VA
2. Line Isolation3750V
3. Switching Frequency40kHz
4. Efficiency at Full Load 70%
SLOPE COMPENSATION
(50 Hz/60Hz)
5. Output Voltage:
A. +5V,±5%; 1A to 4A load
Ripple voltage: 50mV P-P Max
B. +12V,±3%; 0.1A to 0.3A load
Ripple voltage: 100mV P-P Max
C. -12V ,±3%; 0.1A to 0.3A load
Ripple voltage: 100mV P-P Max
A fraction of the oscillator ramp can be resistively
summed with the current sense signal to provide
slope compensation for converters requiring duty
cycles over 50%.
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - May not be currently available - please check http://www.ti.com/productcontent for the latest availability information and additional
product content details.
None: Not yet available Lead (Pb-Free).
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens,
including bromine (Br) or antimony (Sb) above 0.1% of total product weight.
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 3
MECHANICAL DATA
MCER001A – JANUARY 1995 – REVISED JANUARY 1997
JG (R-GDIP-T8)CERAMIC DUAL-IN-LINE
0.400 (10,16)
0.355 (9,00)
0.063 (1,60)
0.015 (0,38)
0.100 (2,54)
8
1
5
4
0.065 (1,65)
0.045 (1,14)
0.020 (0,51) MIN
0.023 (0,58)
0.015 (0,38)
0.280 (7,11)
0.245 (6,22)
0.310 (7,87)
0.290 (7,37)
0.200 (5,08) MAX
Seating Plane
0.130 (3,30) MIN
0°–15°
0.014 (0,36)
0.008 (0,20)
NOTES: A. All linear dimensions are in inches (millimeters).
B. This drawing is subject to change without notice.
C. This package can be hermetically sealed with a ceramic lid using glass frit.
D. Index point is provided on cap for terminal identification.
E. Falls within MIL STD 1835 GDIP1-T8
4040107/C 08/96
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
MECHANICAL DATA
MLCC006B – OCTOBER 1996
FK (S-CQCC-N**) LEADLESS CERAMIC CHIP CARRIER
28 TERMINAL SHOWN
A SQ
B SQ
20
22
23
24
25
19
21
1282627
12
131415161817
0.020 (0,51)
0.010 (0,25)
MIN
0.342
(8,69)
0.442
0.640
0.739
0.938
1.141
A
0.358
(9,09)
0.458
(11,63)
0.660
(16,76)
0.761
(19,32)(18,78)
0.962
(24,43)
1.165
(29,59)
NO. OF
TERMINALS
**
11
10
9
8
7
6
5
432
20
28
44
52
68
84
0.020 (0,51)
0.010 (0,25)
(11,23)
(16,26)
(23,83)
(28,99)
MINMAX
0.307
(7,80)
0.406
(10,31)
0.495
(12,58)
0.495
(12,58)
0.850
(21,6)
1.047
(26,6)
0.080 (2,03)
0.064 (1,63)
B
MAX
0.358
(9,09)
0.458
(11,63)
0.560
(14,22)
0.560
(14,22)
0.858
(21,8)
1.063
(27,0)
0.055 (1,40)
0.045 (1,14)
0.028 (0,71)
0.022 (0,54)
0.050 (1,27)
NOTES: A. All linear dimensions are in inches (millimeters).
B. This drawing is subject to change without notice.
C. This package can be hermetically sealed with a metal lid.
D. The terminals are gold plated.
E. Falls within JEDEC MS-004
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
0.045 (1,14)
0.035 (0,89)
0.045 (1,14)
0.035 (0,89)
4040140/D 10/96
MECHANICAL DATA
MPDI001A – JANUARY 1995 – REVISED JUNE 1999
P (R-PDIP-T8)PLASTIC DUAL-IN-LINE
0.400 (10,60)
0.355 (9,02)
8
5
0.260 (6,60)
0.240 (6,10)
1
0.021 (0,53)
0.015 (0,38)
NOTES: A. All linear dimensions are in inches (millimeters).
B. This drawing is subject to change without notice.
C. Falls within JEDEC MS-001
4
0.070 (1,78) MAX
0.020 (0,51) MIN
0.200 (5,08) MAX
0.125 (3,18) MIN
0.100 (2,54)
0.010 (0,25)
Seating Plane
M
0.325 (8,26)
0.300 (7,62)
0.015 (0,38)
Gage Plane
0.010 (0,25) NOM
0.430 (10,92)
MAX
4040082/D 05/98
For the latest package information, go to http://www.ti.com/sc/docs/package/pkg_info.htm
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
MECHANICAL DATA
MPLC004A – OCT OBER 1994
FN (S-PQCC-J**) PLASTIC J-LEADED CHIP CARRIER
20 PIN SHOWN
Seating Plane
0.004 (0,10)
D
D1
13
4
E1E
8
9
NO. OF
PINS
**
D/E
19
13
18
14
0.032 (0,81)
0.026 (0,66)
0.050 (1,27)
0.008 (0,20) NOM
D1/E1
MINMAXMIN
MAX
D2/E2
MIN
0.180 (4,57) MAX
0.120 (3,05)
0.090 (2,29)
0.020 (0,51) MIN
D2/E2
D2/E2
0.021 (0,53)
0.013 (0,33)
0.007 (0,18)
MAX
M
20
28
44
52
68
84
NOTES: A. All linear dimensions are in inches (millimeters).
B. This drawing is subject to change without notice.
C. Falls within JEDEC MS-018
0.385 (9,78)
0.485 (12,32)
0.685 (17,40)
0.785 (19,94)
0.985 (25,02)
1.185 (30,10)
0.395 (10,03)
0.495 (12,57)
0.695 (17,65)
0.795 (20,19)
0.995 (25,27)
1.195 (30,35)
0.350 (8,89)
0.450 (11,43)
0.650 (16,51)
0.750 (19,05)
0.950 (24,13)
1.150 (29,21)
0.356 (9,04)
0.456 (11,58)
0.656 (16,66)
0.756 (19,20)
0.958 (24,33)
1.158 (29,41)
0.141 (3,58)
0.191 (4,85)
0.291 (7,39)
0.341 (8,66)
0.441 (11,20)
0.541 (13,74)
0.169 (4,29)
0.219 (5,56)
0.319 (8,10)
0.369 (9,37)
0.469 (11,91)
0.569 (14,45)
4040005/B 03/95
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
1
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