SWITCHMODE PULSE WIDTH MODULATION
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SWITCHMODE PULSE WIDTH MODULATION

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Description

Niveau: Supérieur, Master
Device Operating Temperature Range Package SEMICONDUCTOR TECHNICAL DATA SWITCHMODE PULSE WIDTH MODULATION CONTROL CIRCUIT ORDERING INFORMATION TL494CN TL494IN TA = 0° to +70°C TA = – 25° to +85°C Plastic Plastic PIN CONNECTIONS Order this document by TL494/D N SUFFIX PLASTIC PACKAGE CASE 648 CT RT Ground C1 1 Inv Input C2 Q2 E2 E1 1 ≈ 0.1 V Oscillator VCC 5.0 V REF (Top View) Noninv Input Inv Input Vref Output Control VCC Noninv Input Compen/PWN Comp Input Deadtime Control Error Amp + –2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 2 ErrorAmp + – Q1 D SUFFIX PLASTIC PACKAGE CASE 751B (SO–16) TL494CD SO–16 1MOTOROLA ANALOG IC DEVICE DATA ? The TL494 is a fixed frequency, pulse width modulation control circuit designed primarily for SWITCHMODE power supply control. • Complete Pulse Width Modulation Control Circuitry • On–Chip Oscillator with Master or Slave Operation • On–Chip Error Amplifiers • On–Chip 5.0 V Reference • Adjustable Deadtime Control • Uncommitted Output Transistors Rated to 500 mA Source or Sink • Output Control for Push–Pull or Single–Ended Operation • Undervoltage Lockout MAXIMUM RATINGS (Full operating ambient temperature range applies, unless otherwise noted.

  • timing diagram

  • output

  • min typ

  • pwm comparator

  • output control

  • characteristics symbol


Sujets

Informations

Publié par
Nombre de lectures 51

Exrait

Order this document by TL494/D

SWITCHMODEThe TL494 is a fixed frequency, pulse width modulation control circuit
designed primarily for SWITCHMODE power supply control. PULSE WIDTH MODULATION
CONTROL CIRCUIT
• Complete Pulse Width Modulation Control Circuitry
SEMICONDUCTOR
• On–Chip Oscillator with Master or Slave Operation TECHNICAL DATA
• On–Chip Error Amplifiers
• On–Chip 5.0 V Reference
• Adjustable Deadtime Control
D SUFFIX• Uncommitted Output Transistors Rated to 500 mA Source or Sink
PLASTIC PACKAGE• Output Control for Push–Pull or Single–Ended Operation CASE 751B
(SO–16)• Undervoltage Lockout
N SUFFIX
PLASTIC PACKAGE
CASE 648
PIN CONNECTIONS
Noninv Noninv
1 + + 16Input Input
Error ErrorMAXIMUM RATINGS (Full operating ambient temperature range applies, 1 2
Amp AmpInv Inv
– –2 15unless otherwise noted.) Input InputVCC
Rating Symbol TL494C TL494I Unit Compen/PWN 5.0 V3 14 VrefREFComp Input ≈ 0.1 V
Power Supply Voltage V 42 VCC Deadtime Output
4 13Control Control
Collector Output Voltage V , 42 VC1
C 5 12 VV T CCC2
Oscillator
Collector Output Current I , I 500 mA R 6 11 C2C1 C2 T
Q2(Each transistor) (Note 1)
Ground 7 10 E2
Amplifier Input Voltage Range V –0.3 to +42 VIR
Q1
C189 E1
Power Dissipation @ T ≤ 45°C P 1000 mWA D
Thermal Resistance, R 80 °C/WJA (Top View)
Junction–to–Ambient
Operating Junction Temperature T 125 °CJ
Storage Temperature Range T –55 to +125 °C ORDERING INFORMATIONstg
Operating Ambient Temperature Range T °C OperatingA
TL494C 0 to +70 Device Temperature Range Package
TL494I –25 to +85
TL494CD SO–16
T = 0° to +70°CDerating Ambient Temperature T 45 °C AA TL494CN Plastic
NOTE: 1. Maximum thermal limits must be observed.
TL494IN T = – 25° to +85°C PlasticA
 Motorola, Inc. 1996 Rev 1
1MOTOROLA ANALOG IC DEVICE DATA

q
TL494
RECOMMENDED OPERATING CONDITIONS
Characteristics Symbol Min Typ Max Unit
Power Supply Voltage V 7.0 15 40 VCC
Collector Output Voltage V , V – 30 40 VC1 C2
Collector Output Current (Each transistor) I , I – – 200 mAC1 C2
Amplified Input Voltage V –0.3 – V – 2.0 Vin CC
Current Into Feedback Terminal l – – 0.3 mAfb
Reference Output Current l – – 10 mAref
Timing Resistor R 1.8 30 500 kT
Timing Capacitor C 0.0047 0.001 10 FT
Oscillator Frequency f 1.0 40 200 kHzosc
ELECTRICAL CHARACTERISTICS (V = 15 V, C = 0.01 F, R = 12 k , unless otherwise noted.)CC T T
For typical values T = 25°C, for min/max values T is the operating ambient temperature range that applies, unless otherwise noted.A A
Characteristics Symbol Min Typ Max Unit
REFERENCE SECTION
Reference Voltage (I = 1.0 mA) V 4.75 5.0 5.25 VO ref
Line Regulation (V = 7.0 V to 40 V) Reg – 2.0 25 mVCC line
Load Regulation (I = 1.0 mA to 10 mA) Reg – 3.0 15 mVO load
Short Circuit Output Current (V = 0 V) I 15 35 75 mAref SC
OUTPUT SECTION
Collector Off–State Current I – 2.0 100 AC(off)
(V = 40 V, V = 40 V)CC CE
Emitter Off–State Current I – – –100 AE(off)
V = 40 V, V = 40 V, V = 0 V)CC C E
Collector–Emitter Saturation Voltage (Note 2) V
Common–Emitter (V = 0 V, I = 200 mA) V – 1.1 1.3E C sat(C)
Emitter–Follower (V = 15 V, I = –200 mA) V – 1.5 2.5C E sat(E)
Output Control Pin Current
Low State (V ≤ 0.4 V) I – 10 – AOC OCL
High State (V = V ) I – 0.2 3.5 mAOC ref OCH
Output Voltage Rise Time t nsr
Common–Emitter (See Figure 12) – 100 200
Emitter–Follower (See Figure 13) – 100 200
Output Voltage Fall Time t nsf – 25 100 – 40 100
NOTE: 2. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient temperature as possible.
2 MOTOROLA ANALOG IC DEVICE DATA
mmmWmm
WTL494
ELECTRICAL CHARACTERISTICS (V = 15 V, C = 0.01 F, R = 12 k , unless otherwise noted.)CC T T
For typical values T = 25°C, for min/max values T is the operating ambient temperature range that applies, unless otherwise noted.A A
Characteristics Symbol Min Typ Max Unit
ERROR AMPLIFIER SECTION
Input Offset Voltage (V = 2.5 V) V – 2.0 10 mVO (Pin 3) IO
Input Offset Current (V = 2.5 V) I – 5.0 250 nAO (Pin 3) IO
Input Bias Current (V = 2.5 V) I – –0.1 –1.0 AO (Pin 3) IB
Input Common Mode Voltage Range (V = 40 V, T = 25°C) V –0.3 to V –2.0 VCC A ICR CC
Open Loop Voltage Gain ( V = 3.0 V, V = 0.5 V to 3.5 V, R = 2.0 kW) A 70 95 – dBO O L VOL
Unity–Gain Crossover Frequency (V, R = 2.0 k ) f – 350 – kHzO L C–
Phase Margin at Unity–Gain (V = 0.5 V to 3.5 V, R = 2.0 k ) – 65 – deg.O L m
Common Mode Rejection Ratio (V = 40 V) CMRR 65 90 – dBCC
Power Supply Rejection Ratio ( V = 33 V, V = 2.5 V, R = 2.0 k ) PSRR – 100 – dBCC O L
Output Sink Current (V = 0.7 V) I 0.3 0.7 – mAO (Pin 3) O–
Output Source Current (V = 3.5 V) I + 2.0 –4.0 – mAO (Pin 3) O
PWM COMPARATOR SECTION (Test Circuit Figure 11)
Input Threshold Voltage (Zero Duty Cycle) V – 2.5 4.5 VTH
Input Sink Current (V = 0.7 V) I 0.3 0.7 – mA(Pin 3) I–
DEADTIME CONTROL SECTION (Test Circuit Figure 11)
Input Bias Current (Pin 4) (V = 0 V to 5.25 V) I – –2.0 –10 APin 4 IB (DT)
Maximum Duty Cycle, Each Output, Push–Pull Mode DC %max
(V = 0 V, C = 0.01 F, R = 12 k ) 45 48 50Pin 4 T T
(V , C = 0.001 F, R = 30 k ) – 45 50Pin 4 T T
Input Threshold Voltage (Pin 4) V Vth
(Zero Duty Cycle) – 2.8 3.3
(Maximum Duty Cycle) 0 – –
OSCILLATOR SECTION
Frequency (C = 0.001 F, R = 30 k ) f – 40 – kHzT T osc
Standard Deviation of Frequency* (C = 0.001 F, R = 30 k ) f – 3.0 – %T T osc
Frequency Change with Voltage (V = 7.0 V to 40 V, T = 25°C) f ( V) – 0.1 – %CC A osc
Frequency Change with Temperature ( T = T to T ) f ( T) – – 12 %A low high osc
(C = 0.01 F, R = 12 k )T T
UNDERVOLTAGE LOCKOUT SECTION
Turn–On Threshold (V increasing, I = 1.0 mA) V 5.5 6.43 7.0 VCC ref th
TOTAL DEVICE
Standby Supply Current (Pin 6 at V , All other inputs and outputs open) I mAref CC
(V = 15 V) – 5.5 10CC
(V = 40 V) – 7.0 15CC
Average Supply Current mA
(C = 0.01 F, R = 12 k , V = 2.0 V) – 7.0 –T T (Pin 4)
(V = 15 V) (See Figure 12)CC
N
2 (X – X)n
* Standard deviation is a measure of the statistical distribution about the mean as derived from the formula, n = 1
N – 1
3MOTOROLA ANALOG IC DEVICE DATA
DmDmDmmmDmsmmm
S
W
W
D D
D
s W
W
W
W
W
f W
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WTL494
Figure 1. Representative Block Diagram
VOutput Control CC
13
86
D Q Q1Oscillator
9
5 Flip–RT CT Deadtime Flop
Comparator 11Ck Q– Q2
0.12V
+ 10
4
0.7VDeadtime
Control –
12
–+
VCCPWM + 4.9V
0.7mA UVComparator
Lockout Reference

Regulator
+ +
+
1 2
– – 3.5V
12 3 1516 14 7
Gnd
Error Amp Feedback PWM Error Amp Ref.
1 Comparator Input 2 Output
This device contains 46 active transistors.
Figure 2. Timing Diagram
Capacitor CT
Feedback/PWM Comp.
Deadtime Control
Flip–Flop
Clock Input
Flip–Flop
Q
Flip–Flop
Q
Output Q1
Emitter
Output Q2
Emitter
Output
Control
4 MOTOROLA ANALOG IC DEVICE DATATL494
APPLICATIONS INFORMATION
Description may be used to sense power–supply output voltage and
current. The error–amplifier outputs are active high and areThe TL494 is a fixed–frequency pulse width modulation
ORed together at the noninverting input of the pulse–widthcontrol circuit, incorporating the primary building blocks
modulator comparator. With this configuration, the amplifierrequired for the control of a switching power supply. (See
that demands minimum output on time, dominates control ofFigure 1.) An internal–linear sawtooth oscillator is frequency–
the loop.programmable by two external components, R and C . TheT T
When capacitor C is discharged, a positive pulse isapproximate oscillator frequency is determined by: T
generated on the output of the deadtime comparator, which
clocks the pulse–steering flip–flop and inhibits the output
1.1 transistors, Q1 and Q2. With the output–control connected tof ≈osc
R • CT T the reference line, the pulse–steering flip–flop directs the
modulated pulses to each of the two output transistors
For more information refer to Figure 3.
alternately for push–pull operation. The output frequency is
equal to half that of the oscillator. Output drive can also beOutput pulse width modulation is accomplished by
taken from Q1 or Q2, when single–ended operation with acomparison of the positive sawtooth waveform across
maximum on–time of less than 50% is required. This iscapacitor C to either of two control signals. The NOR gates,T
desirable when the output transformer has a ringbackwhich drive output transistors Q1 and Q2, are enabled only
winding with a catch diode used for snubbing. When higherwhen the flip–flop clock–input line is in its low state. This
output–drive currents are required for single–endedhappens only during that portion of time when the sawtooth
operation, Q1 and Q2 may be connected in parallel, and thevoltage is greater than the control signals. Therefore, an
output–mode pin must be tied to ground to disable theincrease in control–signal amplitude causes a corresponding
flip–flop. The output frequency will now be equal to that of thelinear decrease of output pulse width. (Refer to the Timing
oscillator.Diagram shown in Figure 2.)
The TL494 has an internal 5.0 V reference capable ofThe control signals are external inputs that can be fed into
sourcing up to 10 mA of load current for external bias circuits.the deadtime control, the error amplifier inputs, or the
The reference has an internal accuracy of ±5.0% with afeedback input. The deadtime control comparator has an
typical thermal drift of less than 50 mV over an operatingeffective 120 mV input offset which limits the minimum output
temperature range of 0° to 70°C.deadtime to approximately the first 4% of the sawtooth–cycle
time. This would result in a maximum duty cycle on a given
output of 96% with the output control grounded, and 48% with
it connected to the reference line. Additional deadtime may
Figure 3. Oscillator Frequency versusbe imposed on the output by setting the deadtime–control
Timing Resistanceinput to a fixed voltage, ranging between 0 V to 3.3 V.
500 k
Functional Table V = 15 VCCC = 0.001 FT
100 k
Input/Output fout
Output Function =Controls fosc
Grounded Single–ended PWM @ Q1 and Q2 1.0
0.01 F
10 k
@ V Push–pull Operation 0.5ref
The pulse width modulator comparator provides a means
0.1 Ffor the error amplifiers to adjust the output pulse width from
1.0 k
the maximum percent on–time, established by the deadtime
500control input, down to zero, as the voltage at the feedback pin 1.0 k 2.0 k 5.0 k 10 k 20 k 50 k 100 k 200 k 500 k 1.0 M
varies from 0.5 V to 3.5 V. Both error amplifiers have a
R TIMING RESISTANCE ( )T,
common mode input range from –0.3 V to (V – 2V), andCC
5MOTOROLA ANALOG IC DEVICE DATA
Wmm
f , OSCILLATOR FREQUENCY (Hz)
osc
mTL494
Figure 4. Open Loop Voltage Gain and Figure 5. Percent Deadtime versus
Phase versus Frequency Oscillator Frequency
120 20
110 18
V = 15 VCC100
16V = 3.0 VO90 0 C = 0.001 FR = 2.0 k TL 14
80 20
AVOL 1270 40
1060 60
50 80 8.0
40 100
6.0
30 0.001 F120
4.0
20 140
2.010 160
0 180 0
1.0 10 100 1.0 k 10 k 100 k 1.0 M 500 k 1.0 k 10 k 100 k 500 k
f, FREQUENCY (Hz) f , OSCILLATOR FREQUENCY (Hz)osc
Figure 7. Emitter–Follower Configuration
Output Saturation Voltage versusFigure 6. Percent Duty Cycle versus
Emitter CurrentDeadtime Control Voltage
50 1.9
1.8
1 V = 15 V40 CC
V = V 1.72 OC ref
1. C = 0.01 FT
1.62. R = 10 k30 T
2. C = 0.001 FT
1.52. R = 30 kT
20 1.4
1.3
10
1.2
0 1.1
0 1.0 2.0 3.0 3.5 0 100 200 300 400
V , DEADTIME CONTROL VOLTAGE (IV) I EMITTER CURRENT (mA)DT E,
Figure 8. Common–Emitter Configuration
Output Saturation Voltage versus Figure 9. Standby Supply Current
Collector Current versus Supply Voltage
2.0 10
9.01.8
8.0
1.6
7.0
1.4 6.0
1.2 5.0
4.0
1.0
3.0
0.8
2.0
0.6 1.0
0.4 0
0 5.0 10 15 20 25 30 35 400 100 200 300 400
I , COLLECTOR CURRENT (mA) V , SUPPLY VOLTAGE (V)C CC
6 MOTOROLA ANALOG IC DEVICE DATA
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V , SATURATION VOLTAGE (V) % DC, PERCENT DUTY CYCLE (EACH OUTPUT) A , OPEN LOOP VOLTAGE GAIN (dB)
CE(sat) VOL
, EXCESS PHASE (DEGREES)
I , SUPPLY CURRENT (mA) V , SATURATION VOLTAGE (V)
% DT, PERCENT DEADTIME (EACH OUTPUT)
CC CE(sat)
m
m
m
DTL494
Figure 10. Error–Amplifier Characteristics Figure 11. Deadtime and Feedback Control Circuit
V = 15VCC
150 150Error Amplifier
2W 2W+ Under Test
VCCVin
Deadtime C1– Output 1Test
E1
Inputs
Feedback Feedback
Terminal C2 Output 2RT
(Pin 3) E2CT
(+)+
(–) Error
V –ref (+)
Other Error (–)
Amplifier RefOutput
OutControl
50k Gnd
Figure 12. Common–Emitter Configuration Figure 13. Emitter–Follower Configuration
Test Circuit and Waveform Test Circuit and Waveform
15V
15V
RL
C68
V EachC
C Output Q
TransistorEach
CLOutput VQ EE15pF E
Transistor
R CL L
68 15pFE
90%90%
90%90%
VEE
VCC
10%10%
10%10% Gnd
t tr f
t tr f
7MOTOROLA ANALOG IC DEVICE DATATL494
Figure 14. Error–Amplifier Sensing Techniques
VrefVO
To Output
Voltage of
1System
+
R2R1
Error
Amp
1 –
+ 2
Error
3
Amp R1Negative Output Voltage
V –ref
2 R1
V = VO ref VPositive Output Voltage R O2R2
To OutputR1
V = V 1 +O ref Voltage of
R2 System
Figure 15. Deadtime Control Circuit Figure 16. Soft–Start Circuit
Output
Control
R1V Cref SVrefOutput 4
Output 4Q DT
Q DT
R CT T
R2 RS56
0.00130k
80
Max. % on Time, each output ≈ 45 –
R1
1 +
R2
Figure 17. Output Connections for Single–Ended and Push–Pull Configurations
1 1C C
QC 2.4 V ≤ V ≤ VOC ref
Q1 Q 1.0 mA to 250 mA11 1E E
Output Output
1.0 mA toControl Control
500 mA Push–PullSingle–Ended
2 2C C
1.0 mA to 250 mAQ Q0 ≤ V ≤ 0.4 V 2 2OC 2 2E E
QE
8 MOTOROLA ANALOG IC DEVICE DATATL494
Figure 18. Slaving Two or More Control Circuits Figure 19. Operation with V > 40 V Usingin
External Zener
Vref
VR CCS
12V > 40V6 in
R 1N975AT
Master V = 39VZ 5.0V5
CT RefRT
CT 270
Gnd
Vref 7
6
RT Slave
(Additional5
CT Circuits)
Figure 20. Pulse Width Modulated Push–Pull Converter
+V = 8.0V to 20Vin
12 +V = 28 VO
I = 0.2 A1N4934 O471 V TCC+ 1
8 222 TipC– 1 k321M L1
+33k 3
TL494 50Comp
+ 35V0.010.01 15 11 50Tip– C 4.7k2 +25V32
5016
+ 35V1 2OC V DT C R Gnd E EREF T T 1.047 1N4934
13144567910
+
240
4.7k 10 15k4.7k 10k 0.001
All capacitors in F
Test Conditions Results
L1 – 3.5 mH @ 0.3 A
Line Regulation V = 10 V to 40 V 14 mV 0.28%in T1 – Primary: 20T C.T. #28 AWG
T1 – Secondary: 12OT C.T. #36 AWGLoad Regulation V = 28 V, I = 1.0 mA to 1.0 A 3.0 mV 0.06%in O
T1 – Core: Ferroxcube 1408P–L00–3CB
Output Ripple V = 28 V, I = 1.0 A 65 mV pp P.A.R.D.in O
Short Circuit Current V = 28 V, R = 0.1 1.6 Ain L
Efficiency V = 28 V, I = 1.0 A 71%in O
9MOTOROLA ANALOG IC DEVICE DATA
m
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