TL284x, TL384x
CURRENT-MODE PWM CONTROLLERS
SLVS038F JANUARY 1989 REVISED FEBRUARY 2003
D
D
D
D
D
D
D
D
D
D
D
D
Optimized for Off-Line and dc-to-dc
Converters
Low Start-Up Current (<1 mA)
Automatic Feed-Forward Compensation
Pulse-by-Pulse Current Limiting
Enhanced Load-Response Characteristics
Undervoltage Lockout With Hysteresis
Double-Pulse Suppression
High-Current Totem-Pole Output
Internally Trimmed Bandgap Reference
500-kHz Operation
Error Amplifier With Low Output
Resistance
Designed to Be Interchangeable With
UC2842 and UC3842 Series
description/ordering information
D PACKAGE
(TOP VIEW)
COMP
NC
VFB
NC
ISENSE
NC
RT/CT
14
13
12
11
10
REF
NC
VCC
VC
OUTPUT
GND
POWER GROUND
NC No internal connection
D-8 OR P PACKAGE
(TOP VIEW)
COMP
VFB
ISENSE
RT/CT
REF
VCC
OUTPUT
GND
The TL284x and TL384x series of control
integrated circuits provide the features that are
necessary to implement off-line or dc-to-dc fixed-frequency current-mode control schemes, with a minimum
number of external components. Some of the internally implemented circuits are an undervoltage lockout
(UVLO), featuring a start-up current of less than 1 mA, and a precision reference trimmed for accuracy at the
error amplifier input. Other internal circuits include logic to ensure latched operation, a pulse-width modulation
(PWM) comparator (that 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 when it is in the
off state.
Major differences between members of these series are the UVLO thresholds and maximum duty-cycle ranges.
Typical UVLO thresholds of 16 V (on) and 10 V (off) on the TLx842 and TLx844 devices make them ideally suited
to off-line applications. The corresponding typical thresholds for the TLx843 and TLx845 devices are 8.4 V (on)
and 7.6 V (off). The TLx842 and TLx843 devices can operate to duty cycles approaching 100%. A duty-cycle
range of 0 to 50% is obtained by the TLx844 and TLx845 by the addition of an internal toggle flip-flop, which
blanks the output off every other clock cycle.
The TL284x-series devices are characterized for operation from 40C to 85C. The TL384x-series devices are
characterized for operation from 0C to 70C.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
Copyright 2003, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
TL284x, TL384x
CURRENT-MODE PWM CONTROLLERS
SLVS038F JANUARY 1989 REVISED FEBRUARY 2003
ORDERING INFORMATION
ORDERABLE
PART NUMBER
PACKAGE
TA
PDIP ((P))
(8 pin)
SOIC ((D))
(8 pin)
0C to 70C
SOIC ((D))
(14 pin)
PDIP ((P))
(8 pin)
SOIC ((D))
(8 pin)
40C
40C to 85C
SOIC ((D))
(14 pin)
Tube of 50
TL3842P
TL3842P
TL3843P
TL3843P
TL3844P
TL3844P
TL3845P
TL3845P
Tube of 75
TL3842D-8
Reel of 2500
TL3842DR-8
Tube of 75
TL3843D-8
Reel of 2500
TL3843DR-8
Tube of 75
TL3844D-8
Reel of 2500
TL3844DR-8
Tube of 75
TL3845D-8
Reel of 2500
TL3845DR-8
Tube of 50
TL3842D
Reel of 2500
TL3842DR
Tube of 50
TL3843D
Reel of 2500
TL3843DR
Tube of 50
TL3844D
Reel of 2500
TL3844DR
Tube of 50
TL3845D
Reel of 2500
TL3845DR
Tube of 50
TOP-SIDE
MARKING
TL3842
TL3843
TL3844
TL3845
TL3842
TL3843
TL3844
TL3845
TL2842P
TL2842P
TL2843P
TL2843P
TL2844P
TL2844P
TL2845P
TL2845P
Tube of 75
TL2842D-8
Reel of 2500
TL2842DR-8
Tube of 75
TL2843D-8
Reel of 2500
TL2843DR-8
Tube of 75
TL2844D-8
Reel of 2500
TL2844DR-8
Tube of 75
TL2845D-8
Reel of 2500
TL2845DR-8
Tube of 50
TL2842D
Reel of 2500
TL2842DR
Tube of 50
TL2843D
Reel of 2500
TL2843DR
Tube of 50
TL2844D
Reel of 2500
TL2844DR
Tube of 50
TL2845D
Reel of 2500
TL2845DR
TL2842
TL2843
TL2844
TL2845
TL2842
TL2843
TL2844
TL2845
Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines are
available at www.ti.com/sc/package.
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
TL284x, TL384x
CURRENT-MODE PWM CONTROLLERS
SLVS038F JANUARY 1989 REVISED FEBRUARY 2003
functional block diagram
VCC
12
34 V NOM
GND
UVLO
5-V REF
EN
14
REF
Internal
Bias
Vref
Good
Logic
RT/CT
11
10
OSC
VC
OUTPUT
T
Error
Amplifier
VFB
COMP
ISENSE
3
1
5
POWER
GROUND
S
2R
R
R
1V
PWM
Latch
CurrentSense
Comparator
The toggle flip-flop is present only in TL2844, TL2845, TL3844, and TL3845.
Pin numbers shown are for the D (14-pin) package.
POST OFFICE BOX 655303
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TL284x, TL384x
CURRENT-MODE PWM CONTROLLERS
SLVS038F JANUARY 1989 REVISED FEBRUARY 2003
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
Supply voltage (see Note 1) (ICC < 30 mA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self limiting
Analog input voltage range, VI (VFB and ISENSE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3 V to 6.3 V
Output voltage, VO (OUTPUT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 V
Input voltage, VI, (VC, D package only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 V
Supply current, ICC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 mA
Output current, IO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 A
Error amplifier output sink current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 mA
Package thermal impedance, JA (see Notes 2 and 3): D package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86C/W
D-8 package . . . . . . . . . . . . . . . . . . . . . . . . . . 97C/W
P package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85C/W
Virtual junction temperature, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150C
Output energy (capacitive load) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 J
Lead temperature, 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260C
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65C to 150C
Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTES: 1. All voltages are with respect to the device GND terminal.
2. Maximum power dissipation is a function of TJ(max), JA, and TA. The maximum allowable power dissipation at any allowable
ambient temperature is PD = (TJ(max) TA)/JA. Operating at the absolute maximum TJ of 150C can impact reliability.
3. The package thermal impedance is calculated in accordance with JESD 51-7.
recommended operating conditions
MIN
MAX
UNIT
Supply voltage
30
VI, RT/CT
VI, VFB and ISENSE
Input voltage
5.5
Input voltage
5.5
VO, OUTPUT
VO, POWER GROUND
Output voltage
30
Output voltage
0.1
ICC
IO
Supply current, externally limited
25
mA
Average output current
200
mA
IO(ref)
fosc
Reference output current
20
mA
500
kHz
TA
Oscillator frequency
100
TL284x
40
85
TL384x
70
Operating free-air
free air temperature
These recommended voltages for VC and POWER GROUND apply only to the D package.
NOM
VCC and VC
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TL284x, TL384x
CURRENT-MODE PWM CONTROLLERS
SLVS038F JANUARY 1989 REVISED FEBRUARY 2003
electrical characteristics over recommended operating free-air temperature range, VCC = 15 V (see
Note 4), RT = 10 k, CT = 3.3 nF (unless otherwise specified)
reference section
PARAMETER
Output voltage
TEST CONDITIONS
Line regulation
IO = 1 mA,
VCC = 12 V to 25 V
Load regulation
IO = 1 mA to 20 mA
TA = 25C
TL284x
MIN TYP
MAX
4.95
5.05
5.1
20
20
mV
25
25
mV
0.2
0.4
0.2
0.4
mV/C
5.18
Temperature coefficient
of output voltage
Output voltage
with worst-case variation
VCC = 12 V to 25 V,
Output noise voltage
f = 10 Hz to 10 kHz,
Output-voltage long-term drift
IO = 1 mA to 20 mA
4.9
5.1
TA = 25C
After 1000 h at TA = 25C
TL384x
MIN TYP
4.9
4.82
50
Short-circuit output current
30
MAX
UNIT
50
25
25
mV
100
180
30
100
180
mA
MAX
MIN
TL384x
TYP
MAX
52
57
47
10
All typical values are at TA = 25C.
NOTE 4: Adjust VCC above the start threshold before setting it to 15 V.
oscillator section
PARAMETER
TEST CONDITIONS
Oscillator frequency (see Note 5)
Frequency change with supply voltage
TA = 25C
VCC = 12 V to 25 V
MIN
TL284x
TYP
47
Frequency change with temperature
50
UNIT
52
57
kHz
10
Hz/kHz
50
Hz/kHz
Peak-to-peak amplitude at RT/CT
1.7
1.7
V
All typical values are at TA = 25C.
NOTES: 4. Adjust VCC above the start threshold before setting it to 15 V.
5. Output frequency equals oscillator frequency for the TLx842 and TLx843. Output frequency is one-half the oscillator frequency for
the TLx844 and TLx845.
error-amplifier section
PARAMETER
Feedback input voltage
TL284x
MIN TYP
COMP at 2.5 V
2.45
VO = 2 V to 4 V
65
90
65
90
dB
0.7
0.7
MHz
60
70
60
70
dB
mA
0.5
0.8
0.5
0.8
mA
TEST CONDITIONS
Input bias current
Open-loop voltage amplification
Gain-bandwidth product
Supply-voltage rejection ratio
Output sink current
VCC = 12 V to 25 V
VFB at 2.7 V,
COMP at 1.1 V
Output source current
VFB at 2.3 V,
COMP at 5 V
High-level output voltage
VFB at 2.3 V,
RL = 15 k to GND
Low-level output voltage
VFB at 2.7 V,
RL = 15 k to GND
MAX
TL384x
MIN TYP
MAX
2.50
2.55
2.42
2.50
2.58
0.3
0.3
6
0.7
5
1.1
6
0.7
UNIT
V
1.1
All typical values are at TA = 25C.
NOTE 4: Adjust VCC above the start threshold before setting it to 15 V.
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TL284x, TL384x
CURRENT-MODE PWM CONTROLLERS
SLVS038F JANUARY 1989 REVISED FEBRUARY 2003
electrical characteristics over recommended operating free-air temperature range, VCC = 15 V (see
Note 4), RT = 10 k, CT = 3.3 nF (unless otherwise specified) (continued)
current-sense section
MAX
TL384x
MIN TYP
MAX
3.13
2.85
3.15
V/V
1.1
0.9
1.1
10
Delay time to output
150
300
150
All typical values are at TA = 25C.
NOTES: 4. Adjust VCC above the start threshold before setting it to 15 V.
6. These parameters are measured at the trip point of the latch, with VFB at 0 V.
7. Voltage amplification is measured between ISENSE and COMP, with the input changing from 0 V to 0.8 V.
300
ns
PARAMETER
TEST CONDITIONS
Voltage amplification
See Notes 6 and 7
Current-sense comparator threshold
COMP at 5 V,
See Note 6
Supply-voltage rejection ratio
VCC = 12 V to 25 V,
See Note 6
TL284x
MIN TYP
2.85
0.9
70
Input bias current
70
10
UNIT
dB
output section
PARAMETER
TEST CONDITIONS
High level output voltage
High-level
IOH = 20 mA
IOH = 200 mA
Low level output voltage
Low-level
IOL = 20 mA
IOL = 200 mA
Rise time
CL = 1 nF,
Fall time
CL = 1 nF,
TL284x
MIN TYP
MAX
TL384x
MIN TYP
13
13.5
13
13.5
12
13.5
12
13.5
TA = 25C
TA = 25C
MAX
UNIT
V
0.1
0.4
0.1
0.4
1.5
2.2
1.5
2.2
50
150
50
150
ns
50
150
50
150
ns
All typical values are at TA = 25C.
NOTE 4: Adjust VCC above the start threshold before setting it to 15 V.
undervoltage-lockout section
PARAMETER
Start threshold voltage
Minimum operating voltage after startup
MIN
TL284x
TYP
MAX
MIN
TL384x
TYP
MAX
TLx842, TLx844
15
16
17
14.5
16
17.5
TLx843, TLx845
7.8
8.4
7.8
8.4
TLx842, TLx844
10
11
8.5
10
11.5
TLx843, TLx845
7.6
8.2
7.6
8.2
MAX
MIN
UNIT
V
V
All typical values are at TA = 25C.
NOTE 4: Adjust VCC above the start threshold before setting it to 15 V.
pulse-width-modulator section
PARAMETER
Maximum duty cycle
MIN
TL284x
TYP
MAX
TLx842, TLx843
95
97
100
95
97
100
TLx844, TLx845
46
48
50
46
48
50
Minimum duty cycle
All typical values are at TA = 25C.
NOTE 4: Adjust VCC above the start threshold before setting it to 15 V.
TL384x
TYP
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UNIT
TL284x, TL384x
CURRENT-MODE PWM CONTROLLERS
SLVS038F JANUARY 1989 REVISED FEBRUARY 2003
electrical characteristics over recommended operating free-air temperature range, VCC = 15 V (see
Note 4), RT = 10 k, CT = 3.3 nF (unless otherwise specified) (continued)
supply voltage
PARAMETER
TEST CONDITIONS
MIN
TL284x
TYP
Start-up current
MAX
MIN
TL384x
TYP
MAX
UNIT
0.5
0.5
mA
Operating supply current
VFB and ISENSE at 0 V
11
17
11
17
mA
Limiting voltage
ICC = 25 mA
34
34
All typical values are at TA = 25C.
NOTE 4: Adjust VCC above the start threshold before setting it to 15 V.
POST OFFICE BOX 655303
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TL284x, TL384x
CURRENT-MODE PWM CONTROLLERS
SLVS038F JANUARY 1989 REVISED FEBRUARY 2003
APPLICATION INFORMATION
2.5 V
0.5 mA
Error
Amplifier
COMP
Zf
NOTE A:
VFB
Zi
Error amplifier can source or sink up to 0.5 mA.
Figure 1. Error-Amplifier Configuration
Error
Amplifier
IS
(see Note A)
2R
R
COMP
Rf
RS
1V
Current-Sense
Comparator
ISENSE
Cf
GND
NOTE A: Peak current (IS) is determined by the formula:
1 V
I S(max)
RS
A small RC filter formed by resistor Rf and capacitor Cf may be required to suppress switch transients.
Figure 2. Current-Sense Circuit
REF
RT
(see Note A)
RT/CT
CT
GND
NOTE A: For RT > 5 k: f
[ R1.72C
T
Figure 3. Oscillator Section
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DALLAS, TEXAS 75265
TL284x, TL384x
CURRENT-MODE PWM CONTROLLERS
SLVS038F JANUARY 1989 REVISED FEBRUARY 2003
APPLICATION INFORMATION
TIMING RESISTANCE
vs
FREQUENCY
DEAD TIME
vs
TIMING CAPACITANCE
100
100
CT = 10 nF
VCC = 15 V
RT 5 k
TA = 25C
40
CT = 4.7 nF
CT = 22 nF
R T Timing Resistance k
Dead Time s
40
10
CT = 1 nF
CT = 22 nF
10
CT = 47 nF
CT = 100 nF
0.4
VCC = 15 V
TA = 25C
1
100
0.1
0
10
40
100
1k
10 k
100 k
1M
f Frequency Hz
CT Timing Capacitance nF
Figure 4
Figure 5
open-loop laboratory test fixture
In the open-loop laboratory test fixture (see Figure 6), high peak currents associated with loads necessitate
careful grounding techniques. Timing and bypass capacitors should be connected close to the GND terminal
in a single-point ground. The transistor and 5-k potentiometer sample the oscillator waveform and apply an
adjustable ramp to the ISENSE terminal.
REF
RT
4.7 k
VCC
2N2222
100 k
1 k
Error Amplifier
Adjust
DUT
VFB
5 k
REF
COMP
ISENSE
0.1 F
TL284x
TL384x
VCC
OUTPUT
0.1 F
1 k, 1 W
OUTPUT
4.7 k
ISENSE
Adjust
RT/CT
GND
GND
CT
Figure 6. Open-Loop Laboratory Test Fixture
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
TL284x, TL384x
CURRENT-MODE PWM CONTROLLERS
SLVS038F JANUARY 1989 REVISED FEBRUARY 2003
APPLICATION INFORMATION
shutdown technique
The PWM controller (see Figure 7) can be shut down by two methods: either raise the voltage at ISENSE above
1 V or pull the COMP terminal 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 dominant so that the output
remains low until the next clock cycle after the shutdown condition at the COMP or ISENSE terminal is removed.
In one example, an externally latched shutdown can be accomplished by adding an SCR that resets by cycling
VCC below the lower UVLO threshold. At this point, the reference turns off, allowing the SCR to reset.
1 k
REF
COMP
Shutdown
330
ISENSE
500
Shutdown
To Current-Sense
Resistor
Figure 7. Shutdown Techniques
A fraction of the oscillator ramp can be summed resistively with the current-sense signal to provide slope
compensation for converters requiring duty cycles over 50% (see Figure 8). Note that capacitor C forms a filter
with R2 to suppress the leading-edge switch spikes.
REF
0.1 F
RT
RT/CT
CT
R1
ISENSE
R2
ISENSE
C
Figure 8. Slope Compensation
10
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RSENSE
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