ETC UC2845AQ

UC2842AQ, UC2843AQ, UC2844AQ, UC2845AQ
CURRENT-MODE PWM CONTROLLER
SGLS164 – APRIL 2003
D Extended Temperature Performance of
D 8-PIN PACKAGE
(TOP VIEW)
–40°C to 125°C
D Optimized for Off-line and DC to DC
D
D
D
D
D
D
D
D
D
D
D
Converters
Low Start Up Current (<0.5 mA)
Trimmed Oscillator Discharge Current
Automatic Feed Forward Compensation
Pulse-by-Pulse Current Limiting
Enhanced Load Response Characteristics
Under-Voltage Lockout With Hysteresis
Double Pulse Suppression
High Current Totem Pole Output
Internally Trimmed Bandgap Reference
500 kHz Operation
Low RO Error Amp
COMP
VFB
1
8
2
7
ISENSE
RT/CT
3
6
4
5
VREF
VCC
OUTPUT
GND
D 14-PIN PACKAGE
(TOP VIEW)
COMP
NC
VFB
NC
1
14
2
13
3
12
4
11
ISENSE
NC
RT/CT
5
10
6
9
7
8
VREF
NC
VCC
VC
OUTPUT
GND
PWR GND
description
The UC2842A/3A/4A/5A family of control ICs is a pin for pin compatible improved version of the UC2842/3/4/5
family. Providing the necessary features to control current mode switched mode power supplies, this family has the
following improved features. Start up current is guaranteed to be less than 0.5 mA. Oscillator discharge is trimmed
to 8.3 mA. During under voltage lockout, the output stage can sink at least 10 mA at less than 1.2 V for VCC over
5 V.
The difference between members of this family are shown in the table below.
PART NUMBER
UVLO ON
UVLO OFF
MAXIMUM DUTY CYCLE
UC2842A
16 V
10 V
<100%
UC2843A
8.5 V
7.9 V
<100%
UC2844A
16 V
10 V
<50%
UC2845A
8.5 V
7.9 V
<50%
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
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1
UC2842AQ, UC2843AQ, UC2844AQ, UC2845AQ
CURRENT-MODE PWM CONTROLLER
SGLS164 – APRIL 2003
ORDERING INFORMATION†
TA
40°C to 125°C
–40°C
ORDERABLE
PART NUMBER
PACKAGE‡
TOP-SIDE
MARKING
SOIC-8 – D8
Tape and reel
UC2842AQD8R
2842AQ
SOIC-8 – D8
Tube
UC2842AQD8
2842AQ
SOIC-14 – D
Tape and reel
UC2842AQDR
2842AQ
SOIC-14 – D
Tube
UC2842AQD
2842AQ
SOIC-8 – D8
Tape and reel
UC2843AQD8R
2843AQ
SOIC-8 – D8
Tube
UC2843AQD8
2843AQ
SOIC-14 – D
Tape and reel
UC2843AQDR
2843AQ
SOIC-14 – D
Tube
UC2843AQD
2843AQ
SOIC-8 – D8
Tape and reel
UC2844AQD8R
2844AQ
SOIC-8 – D8
Tube
UC2844AQD8
2844AQ
SOIC-14 – D
Tape and reel
UC2844AQDR
2844AQ
SOIC-14 – D
Tube
UC2844AQD
2844AQ
SOIC-8 – D8
Tape and reel
UC2845AQD8R
2845AQ
SOIC-8 – D8
Tube
UC2845AQD8
2845AQ
SOIC-14 – D
Tape and reel
UC2845AQDR
2845AQ
SOIC-14 – D
Tube
UC2845AQD
2845AQ
† Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines
are available at www.ti.com/sc/package.
block diagram
NOTES: 1. A = DIL-8 Pin Number. B = SO-14 Pin Number.
2. Toggle flip flop used only in 2844A and 2845A.
2
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UC2842AQ, UC2843AQ, UC2844AQ, UC2845AQ
CURRENT-MODE PWM CONTROLLER
SGLS164 – APRIL 2003
Ordering Information
UC 284
4
A
Q
D
R
TAPE and REEL INDICATOR
PACKAGE
D = Plastic SOIC, 14 pin
D8 = Plastic SOIC, 8 pin
AUTOMOTIVE TEMPERATURE RANGE INDICATOR
IMPROVED PERFORMANCE INDICATOR
PRODUCT OPTION
2 through 5
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
3
UC2842AQ, UC2843AQ, UC2844AQ, UC2845AQ
CURRENT-MODE PWM CONTROLLER
SGLS164 – APRIL 2003
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)†‡
VCC voltage (low impedance source) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 V
VCC voltage (ICC mA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . self limiting
Output current, IO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±1 A
Output energy (capacitive load) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 µJ
Analog Inputs (pins 3, 5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to 6.3 V
Error Amp Output Sink current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 mA
Power Dissipation at TA < +25_C (D package) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 W
Package thermal impedance, θJA (see Note 1): D (8-pin) package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97°C/W
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65_C to 150_C
Lead temperature soldering 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . 260_C
† 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.
‡ Unless otherwise indicated, voltages are reference to ground and currents are positive into and negative out of the specified terminals.
NOTE 1: Long term high–temperature storage and/or extended use at maximum recommended operating conditions may result in a reduction of
overall device life. See http://www.ti.com/ep_quality for additional information on enhanced plastic packaging.
electrical characteristics, TA = –40_C to 125_C, VCC = 15 V (see Note 1), RT = 10 kΩ, CT = 3.3 nF, and
TA = TJ (unless otherwise stated)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Reference Section
Output voltage
TJ = 25_C,
Line regulation voltage
Load regulation voltage
Temperature stability
See Notes 2 and 3
Total output variation voltage
Line, Load, Temp.
Output noise voltage
f = 10 Hz to 10 kHz,
See Note 2
Long term stability
1000 hours,
4.95
5.0
5.05
VIN = 12 V to 25 V
6
20
mV
IO = 1 mA to 20 mA
6
25
mV
0.2
0.4
mV/_C
5.1
V
IO = 1 mA
4.9
See Note 2
5
25
mV
–30
–100
–180
mA
47
52
57
kHz
0.2
1
%
TA = 125_C
Output short-circuit current
µV
50
TJ = 25_C
V
Oscillator Section
Initial accuracy
See Note 4
Voltage stability
VCC = 12 V to 25 V
Temperature stability
TA = MIN to MAX,
See Note 2
5
%
Amplitude peak-to-peak
V pin 7,
See Note 2
1.7
V
Discharge current
V pin 7 = 2 V,
V
See Note 5
4
POST OFFICE BOX 655303
TJ = 25_C
TJ = 25_C
7.8
TJ = Full range
7.5
• DALLAS, TEXAS 75265
8.3
8.8
8.8
mA
UC2842AQ, UC2843AQ, UC2844AQ, UC2845AQ
CURRENT-MODE PWM CONTROLLER
SGLS164 – APRIL 2003
electrical characteristics, TA = –40_C to 125_C, VCC = 15 V (see Note 1), RT = 10 kΩ, CT = 3.3 nF, and
TA = TJ (unless otherwise stated)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Error Amplifier Section
Input voltage
COMP = 2.5 V
2.45
Input bias current
Open loop voltage gain (AVOL)
VO = 2 V to 4 V
Unity gain bandwidth
See Note 2
PSRR
VCC = 12 V to 25 V
Output sink current
FB = 2.7 V,
COMP = 1.1 V
Output source current
FB = 2.3 V,
COMP = 5 V
VOUT high
FB = 2.3 V,
RL = 15 kΩ to GND
VOUT low
FB = 2.7 V,
RL = 15 kΩ to VREF
TJ = 25_C
2.5
2.55
V
–0.3
–1
µA
65
90
dB
0.7
1
MHz
60
70
dB
2
6
mA
–0.5
–0.8
mA
5
6
V
0.7
1.1
V
2.85
3
3.15
V/V
0.9
1
1.1
V
Current Sense Section
Gain
See Notes 6 and 7
Maximum input signal
COMP = 5 V,
PSRR
VCC = 12 V to 25 V,See Note 6
See Note 6
70
–2
–10
µA
150
300
ns
IOUT = 20 mA
0.1
0.4
IOUT = 200 mA
15
2.2
Input bias current
Delay to output
dB
ISENSE = 0 V to 2 V,
See Note 2
Output Section (OUT)
Low level output voltage
Low-level
High level output voltage
High-level
IOUT = –20 mA
13
13.5
IOUT = –200 mA
12
13.5
V
V
Rise time
CL = 1 nF,
See Note 2
TJ = 25_C
50
150
ns
Fall time
CL = 1 nF,
See Note 2
TJ = 25_C
50
150
ns
UVLO saturation
VCC = 5 V,
IOUT = 10 mA
0.7
1.2
V
Undervoltage Lockout Section
Start threshold
Minimum operation voltage after turn on
POST OFFICE BOX 655303
UC2842A,
UC2844A
15
16
17
UC2843A,
UC2845A
7.8
8.4
9
UC2842A,
UC2844A
9
10
11
UC2843A,
UC2845A
7
7.6
8.2
• DALLAS, TEXAS 75265
V
V
5
UC2842AQ, UC2843AQ, UC2844AQ, UC2845AQ
CURRENT-MODE PWM CONTROLLER
SGLS164 – APRIL 2003
electrical characteristics, TA = –40_C to 125_C, VCC = 15 V (see Note 1), RT = 10 kΩ, CT = 3.3 nF, and
TA = TJ (unless otherwise stated)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
PWM Section
Maximum duty cycle
UC2842A, UC2843A
94
96
100
UC2844A, UC2845A
47
48
50
Minimum duty cycle
0
%
%
Total Standby Current
Start-up current
Operating supply current
FB = 0 V,
SENSE = 0 V
0.3
0.5
mA
11
17
mA
VCC internal zener voltage
ICC = 25 mA
30
34
V
NOTES: 1. Adjust VCC above the start threshold before setting at 15 V.
2. Not production tested.
3. Temperature stability, sometimes referred to as average temperature coefficient, is described by the equation:
V
(max) – VREF (min). VREF (max) and VREF (min) are the maximum and minimum reference voltage measured
Temp Stability = REF
TJ (max) – TJ (min)
over the appropriate temperature range. Note that the extremes in voltage do not necessarily occur at the extremes in temperature.
4. Output frequency equals oscillator frequency for the UC2842A and UC2843A. Output frequency is one half oscillator frequency for the
UC2844A and UC2845A.
5. This parameter is measured with RT = 10 kΩ to VREF. This contributes approximately 300 µA of current to the measurement. The total
current flowing into the RT/C pin will be approximately 300 µA higher than the measured value.
6. Parameter measured at trip point of latch with VFB at 0 V.
7. Gain is defined by:
DVCOMP ; 0 v VSENSE v 0.8 V.
A=
DVSENSE
PA
RAMETER MEASUREMENT INFORMATION
Error Amp can source and sink up to 0.5 mA, and sink up to 2 mA.
Figure 1. Error Amp Configuration
6
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UC2842AQ, UC2843AQ, UC2844AQ, UC2845AQ
CURRENT-MODE PWM CONTROLLER
SGLS164 – APRIL 2003
PARAMETER MEASUREMENT INFORMATION
During UVLO, the Output is low.
Figure 2. Under Voltage Lockout
Peak Current (Is) is Determined By The Formula:
IsmaxȀ 1.0V
RS
A small RC filter may be required to supress switch transients.
Figure 3. Current Sense Circuit
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7
UC2842AQ, UC2843AQ, UC2844AQ, UC2845AQ
CURRENT-MODE PWM CONTROLLER
SGLS164 – APRIL 2003
PARAMETER MEASUREMENT INFORMATION
Error Amplifier Open-Loop Frequency Response
Output Saturation Characteristics
Figure 5
Figure 4
AP
PLICATION INFORMATION
Oscillator Frequency vs Timing Resistance
Figure 6. Oscillator
8
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
Maximum Duty Cycle vs Timing Resistor
UC2842AQ, UC2843AQ, UC2844AQ, UC2845AQ
CURRENT-MODE PWM CONTROLLER
SGLS164 – APRIL 2003
APPLICATION INFORMATION
High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypass capacitors should be
connected close to pin 5 in a single point ground. The transistor and 5k potentiometer are used to sample the oscillator waveform and apply an
adjustable ramp to pin 3.
Figure 7. Open-Loop Laboratory Text Fixture
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%.
Note that capacitor, C, forms a filter with R2 to suppress the
leading edge switch spikes.
Figure 8. Slope Complression
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9
UC2842AQ, UC2843AQ, UC2844AQ, UC2845AQ
CURRENT-MODE PWM CONTROLLER
SGLS164 – APRIL 2003
APPLICATION INFORMATION
Power Supply Specifications
1.
2.
3.
4.
5.
Input Voltage
95VAC to 130VAC (50Hz/60Hz)
Line Isolation
3750V
Switching Frequency 40 kHz
Efficiency, Full Load
70%
Output Voltage:
A. +5V, ±5%; 1A to 4A Load
B. +12V, ±3%; 0.1A to 0.3A Load Ripple voltage: 100 mV P-P Max
C. –12V, ±3%; 0.1A to 0.3A Load Ripple voltage: 100 mV P-P Max
Figure 9. Off-Line Flyback Regulator
10
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MECHANICAL DATA
MSOI002B – JANUARY 1995 – REVISED SEPTEMBER 2001
D (R-PDSO-G**)
PLASTIC SMALL-OUTLINE PACKAGE
8 PINS SHOWN
0.020 (0,51)
0.014 (0,35)
0.050 (1,27)
8
0.010 (0,25)
5
0.008 (0,20) NOM
0.244 (6,20)
0.228 (5,80)
0.157 (4,00)
0.150 (3,81)
Gage Plane
1
4
0.010 (0,25)
0°– 8°
A
0.044 (1,12)
0.016 (0,40)
Seating Plane
0.010 (0,25)
0.004 (0,10)
0.069 (1,75) MAX
PINS **
0.004 (0,10)
8
14
16
A MAX
0.197
(5,00)
0.344
(8,75)
0.394
(10,00)
A MIN
0.189
(4,80)
0.337
(8,55)
0.386
(9,80)
DIM
4040047/E 09/01
NOTES: A.
B.
C.
D.
All linear dimensions are in inches (millimeters).
This drawing is subject to change without notice.
Body dimensions do not include mold flash or protrusion, not to exceed 0.006 (0,15).
Falls within JEDEC MS-012
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1
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Copyright  2003, Texas Instruments Incorporated