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Número de pieza | MC33023 | |
Descripción | High Speed Single-Ended PWM Controller | |
Fabricantes | Motorola Semiconductors | |
Logotipo | ||
Hay una vista previa y un enlace de descarga de MC33023 (archivo pdf) en la parte inferior de esta página. Total 19 Páginas | ||
No Preview Available ! High Speed Single-Ended
PWM Controller
The MC34023 series are high speed, fixed frequency, single–ended pulse
width modulator controllers optimized for high frequency operation. They are
specifically designed for Off–Line and DC–to–DC converter applications
offering the designer a cost–effective solution with minimal external
components. These integrated circuits feature an oscillator, a temperature
compensated reference, a wide bandwidth error amplifier, a high speed
current sensing comparator, and a high current totem pole output ideally
suited for driving a power MOSFET.
Also included are protective features consisting of input and reference
undervoltage lockouts each with hysteresis, cycle–by–cycle current limiting,
and a latch for single pulse metering.
The flexibility of this series allows it to be easily configured for either
current mode or voltage mode control.
• 50 ns Propagation Delay to Output
• High Current Totem Pole Output
• Wide Bandwidth Error Amplifier
• Fully–Latched Logic with Double Pulse Suppression
• Latching PWM for Cycle–By–Cycle Current Limiting
• Soft–Start Control with Latched Overcurrent Reset
• Input Undervoltage Lockout with Hysteresis
• Low Start–Up Current (500 µA Typ)
• Internally Trimmed Reference with Undervoltage Lockout
• 90% Maximum Duty Cycle (Externally Adjustable)
• Precision Trimmed Oscillator
• Voltage or Current Mode Operation to 1.0 MHz
• Functionally Similar to the UC3823
Order this document by MC34023/D
MC34023
MC33023
16
1
P SUFFIX
PLASTIC PACKAGE
CASE 648
16
1
DW SUFFIX
PLASTIC PACKAGE
CASE 751G
(SO–16L)
PIN CONNECTIONS
16
Vref
4
Clock
5
RT
6
CT
7
Ramp
Error Amp 3
Output
Noninverting
Input
2
Inverting
Input
1
8
Soft–Start
Simplified Application
Oscillator
5.1V
Reference
UVLO
Latching
Error PWM
Amp
Soft–Start
10 Ground
This device contains 176 active transistors.
MOTOROLA ANALOG IC DEVICE DATA
15
VCC
13
VC
14
Output
12
Power
Ground
11
Current
9
Limit Ref
Current
Limit/
Shutdown
Error Amp
Inverting Input
Error Amp
Noninverting Input
Error Amp Output
1
2
3
16 Vref
15 VCC
14 Output
Clock 4
RT 5
CT 6
Ramp 7
Soft–Start 8
13 VC
12 Power Ground
11 Current Limit
Reference
10 Ground
9 Current Limit/
Shutdown
(Top View)
ORDERING INFORMATION
Device
MC33023P
MC33023DW
MC34023P
Operating
Temperature Range Package
Plastic DIP
TA = – 40° to +105°C
SO–16L
TA = 0° to +70°C Plastic DIP
© Motorola, Inc. 1996
Rev 2
1
1 page MC34023 MC33023
Figure 7. Reference Voltage Change
versus Source Current
0
– 5.0
VCC = 15 V
– 10
– 15
TA = – 55°C
TA = +125°C
TA = + 25°C
– 20
– 25
– 30
0
10 20 30 40
ISource, SOURCE CURRENT (mA)
50
Figure 8. Reference Short Circuit Current
versus Temperature
66
65.6 VCC = 15 V
65.2
64.8
64.4
64
– 55 – 25 0 25 50 75 100
TA, AMBIENT TEMPERATURE (°C)
125
Figure 9. Reference Line Regulation
Figure 10. Reference Load Regulation
Vref LINE REGULATION 10 V to 24 V
(2.0 ms/DIV)
Vref LOAD REGULATION 1.0 mA to 10 mA
(2.0 ms/DIV)
Figure 11. Current Limit Comparator Input
Offset Voltage versus Temperature
100
60 VCC = 15 V
Pin 11(14) = 1.1 V
20
– 20
– 60
– 100
– 55 – 25
0 25 50 75 100
TA, AMBIENT TEMPERATURE (°C)
125
Figure 12. Shutdown Comparator Threshold
Voltage versus Temperature
1.50
1.46 VCC = 15 V
1.42
1.38
1.34
1.30
– 55
– 25 0 25 50 75 100
TA, AMBIENT TEMPERATURE (°C)
125
MOTOROLA ANALOG IC DEVICE DATA
5
5 Page MC34023 MC33023
Figure 23. Resistive Current Sensing
Figure 24. Primary Side Current Sensing
9 ISense
9 Rw ISense
The addition of an RC filter will eliminate instability caused by the
leading edge spike on the current waveform. This sense signal can also
be used at the ramp input pin for current mode control. For ramp
compensation it is necessary to know the gain of the current feedback
loop. If a transformer is used, the gain can be calculated by:
+Ai
RSense
turns ratio
The addition of an RC filter will eliminate instability caused by the
leading edge spike on the current waveform. This sense signal can also
be used at the ramp input pin for current mode control. For ramp
compensation it is necessary to know the gain of the current feedback
loop. The gain can be calculated by:
+Ai
Rw
turns ratio
Figure 25A. Slope Compensation (Noise Sensitive)
4
5
6
CT C1
Oscillator
Current Sense
Information
R1
R2
7
3
1.25 V
This method of slope compensation is easy to implement, however, it
is noise sensitive. Capacitor C1 provides AC coupling. The oscillator
signal is added to the current signal by a voltage divider consisting of
resistors R1 and R2.
Figure 25B. Slope Compensation (Noise Immune)
Current Sense
Transformer
Rw
Output
RM CM
Rf
Cf
Ramp
Input
7
1.25 V
3
Figure 25.
Current Sense
Resistor
Output
Ramp
Input
RM
7
1.25 V
CM
Rf
Cf
3
When only one output is used, this method of slope compensation can be used and it is relatively noise immune. Resistor RM and capacitor CM provide the added
slope necessary. By choosing RM and CM with a larger time constant than the switching frequency, you can assume that its charge is linear. First choose CM, then
RM can be adjusted to achieve the required slope. The diode provides a reset pulse at the ramp input at the end of every cycle. The charge current IM can be calculated
by IM = CMSe. Then RM can be calculated by RM = VCC/IM.
MOTOROLA ANALOG IC DEVICE DATA
11
11 Page |
Páginas | Total 19 Páginas | |
PDF Descargar | [ Datasheet MC33023.PDF ] |
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