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零件编号 | MC33167 | ||
描述 | (MC33167 / MC34167) Step-Up/Down/Inverting Switching Regulators | ||
制造商 | ON Semiconductor | ||
LOGO | |||
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MC34167, MC33167
5.0 A, Step−Up/Down/
Inverting Switching
Regulators
The MC34167, MC33167 series are high performance fixed
frequency power switching regulators that contain the primary
functions required for dc−to−dc converters. This series was
specifically designed to be incorporated in step−down and
voltage−inverting configurations with a minimum number of external
components and can also be used cost effectively in step−up
applications.
These devices consist of an internal temperature compensated
reference, fixed frequency oscillator with on−chip timing components,
latching pulse width modulator for single pulse metering, high gain
error amplifier, and a high current output switch.
Protective features consist of cycle−by−cycle current limiting,
undervoltage lockout, and thermal shutdown. Also included is a low
power standby mode that reduces power supply current to 36 mA.
Features
• Output Switch Current in Excess of 5.0 A
• Fixed Frequency Oscillator (72 kHz) with On−Chip Timing
• Provides 5.05 V Output without External Resistor Divider
• Precision 2% Reference
• 0% to 95% Output Duty Cycle
• Cycle−by−Cycle Current Limiting
• Undervoltage Lockout with Hysteresis
• Internal Thermal Shutdown
• Operation from 7.5 V to 40 V
• Standby Mode Reduces Power Supply Current to 36 mA
• Economical 5−Lead TO−220 Package with Two Optional Leadforms
• Also Available in Surface Mount D2PAK Package
• Moisture Sensitivity Level (MSL) Equals 1
• Pb−Free Packages are Available
ILIMIT
Vin
4
Oscillator
PWM
Thermal
S
Q
R
UVLO
Reference
EA
2
1
35
This device contains 143 active transistors.
Figure 1. Simplified Block Diagram
(Step Down Application)
L
VO
5.05 V/
5.0 A
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MARKING
DIAGRAMS
1
5
TO−220
TH SUFFIX
CASE 314A
MC
3x167T
AWLYWWG
Heatsink surface connected to Pin 3
1
5
TO−220
TV SUFFIX
CASE 314B
MC
3x167T
AWLYWWG
TO−220
1
T SUFFIX
CASE 314D
5
Pin 1. Voltage Feedback Input
2. Switch Output
3. Ground
4. Input Voltage/VCC
5. Compensation/Standby
MC
3x167T
AWLYWWG
D2PAK
MC
1
D2T SUFFIX
CASE 936A
3x167T
AWLYWWG
5
Heatsink surface (shown as
terminal 6 in case outline
1
drawing) is connected to Pin 3
5
x = 3 or 4
A = Assembly Location
WL = Wafer Lot
Y = Year
WW = Work Week
G = Pb−Free Package
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 17 of this data sheet.
© Semiconductor Components Industries, LLC, 2005
November, 2005 − Rev. 7
1
Publication Order Number:
MC34167/D
MC34167, MC33167
Switch Output
The output transistor is designed to switch a maximum of
40 V, with a minimum peak collector current of 5.5 A. When
configured for step−down or voltage−inverting applications,
as in Figures 19 and 23, the inductor will forward bias the
output rectifier when the switch turns off. Rectifiers with a
high forward voltage drop or long turn on delay time should
not be used. If the emitter is allowed to go sufficiently
negative, collector current will flow, causing additional
device heating and reduced conversion efficiency. Figure 9
shows that by clamping the emitter to 0.5 V, the collector
current will be in the range of 100 mA over temperature. A
1N5825 or equivalent Schottky barrier rectifier is
recommended to fulfill these requirements.
Undervoltage Lockout
An Undervoltage Lockout comparator has been
incorporated to guarantee that the integrated circuit is fully
functional before the output stage is enabled. The internal
reference voltage is monitored by the comparator which
enables the output stage when VCC exceeds 5.9 V. To prevent
erratic output switching as the threshold is crossed, 0.9 V of
hysteresis is provided.
Thermal Protection
Internal Thermal Shutdown circuitry is provided to protect
the integrated circuit in the event that the maximum junction
temperature is exceeded. When activated, typically at 170°C,
the latch is forced into a ‘reset’ state, disabling the output
switch. This feature is provided to prevent catastrophic
failures from accidental device overheating. It is not
intended to be used as a substitute for proper heatsinking.
The MC34167 is contained in a 5−lead TO−220 type package.
The tab of the package is common with the center pin (Pin 3)
and is normally connected to ground.
DESIGN CONSIDERATIONS
Do not attempt to construct a converter on wire−wrap
or plug−in prototype boards. Special care should be taken
to separate ground paths from signal currents and ground
paths from load currents. All high current loops should be
kept as short as possible using heavy copper runs to
minimize ringing and radiated EMI. For best operation, a
tight component layout is recommended. Capacitors Cin,
CO, and all feedback components should be placed as close
to the IC as physically possible. It is also imperative that the
Schottky diode connected to the Switch Output be located as
close to the IC as possible.
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8
MC34167, MC33167
Table 1. Design Equations
Calculation
Step−Down
Step−Up/Down
Voltage−Inverting
ton
toff
(Notes 1, 2)
Vout ) VF
Vin * Vsat * Vout
Vout ) VF1 ) VF2
Vin * VsatQ1 * VsatQ2
|Vout| ) VF
Vin * Vsat
ton
Duty Cycle
(Note 3)
ton
toff
ǒ Ǔfosc
ton
toff
)
1
ton fosc
ton
toff
ǒ Ǔfosc
ton
toff
)
1
ton fosc
ton
toff
ǒ Ǔfosc
ton
toff
)
1
ton fosc
IL avg
Iout
ǒ ǓIout
ton
toff
)
1
ǒ ǓIout
ton
toff
)
1
Ipk(switch)
L
Vripple(pp)
IL avg
)
DIL
2
ǒ ǓVin * Vsat * Vout
DIL
ton
Ǹǒ ǓDIL
1
8foscCo
2 ) (ESR)2
IL avg
)
DIL
2
ǒ ǓVin * VsatQ1 * VsatQ2
DIL
ton
ǒ ǓǸǒ Ǔton
toff
)
1
1
foscCo
2 ) (ESR)2
IL avg
)
DIL
2
ǒ ǓVin * Vsat
DIL
ton
ǒ ǓǸǒ Ǔton
toff
)
1
1
foscCo
2 ) (ESR)2
ǒ ǓVout
Vref
R2
R1
)
1
ǒ ǓVref
R2
R1
)
1
ǒ ǓVref
R2
R1
)
1
1. Vsat − Switch Output source saturation voltage, refer to Figure 8.
2. VF − Output rectifier forward voltage drop. Typical value for 1N5822 Schottky barrier rectifier is 0.35 V.
3. Duty cycle is calculated at the minimum operating input voltage and must not exceed the guaranteed minimum DC(max) specification of 0.92.
The following converter characteristics must be chosen:
Vout − Desired output voltage.
Iout − Desired output current.
DIL − Desired peak−to−peak inductor ripple current. For maximum output current especially when the duty cycle is greater than 0.5,
it is suggested that DIL be chosen minimum current limit threshold of 5.5 A. If the design goal is to use a minimum inductance
value, let DIL = 2 (IL avg). This will proportionally reduce the converter’s output current capability.
Vripple(pp) − Desired peak−to−peak output ripple voltage. For best performance, the ripple voltage should be kept to less than 2% of Vout.
Capacitor CO should be a low equivalent series resistance (ESR) electrolytic designed for switching regulator applications.
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页数 | 20 页 | ||
下载 | [ MC33167.PDF 数据手册 ] |
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