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參數(shù)資料
| 型號： | MC33023DWG |
| 廠商： | ON SEMICONDUCTOR |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | High Speed Single−Ended PWM Controller |
| 中文描述： | 2 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | LEAD FREE, SOIC-16 |
| 文件頁數(shù)： | 9/18頁 |
| 文件大?。?/td> | 450K |
| 代理商： | MC33023DWG |
MC34023, MC33023
http://onsemi.com
9
OPERATING DESCRIPTION
The MC33023 and MC34023 series are high speed, fixed
frequency, singleended pulse width modulator controllers
optimized for high frequency operation. They are
specifically designed for OffLine and DCtoDC
converter applications offering the designer a cost effective
solution
with
minimal
representative block diagram is shown in Figure 19.
external
components.
A
Oscillator
The oscillator frequency is programmed by the values
selected for the timing components R
T
and C
T
. The R
T
pin
is set to a temperature compensated 3.0 V. By selecting the
value of R
T
, the charge current is set through a current mirror
for the timing capacitor C
T
. This charge current runs
continuously through C
T
. The discharge current is ratioed to
be 10 times the charge current, which yields the maximum
duty cycle of 90%. C
T
is charged to 2.8 V and discharged to
1.0 V During the discharge of C
T
, the oscillator generates an
internal blanking pulse that resets the PWM Latch and,
inhibits the outputs. The threshold voltage on the oscillator
comparator is trimmed to guarantee an oscillator accuracy
of 5.0% at 25
°
C.
Additional dead time can be added by externally
increasing the charge current to C
T
as shown in Figure 24.
This changes the charge to discharge ratio of C
T
which is set
internally to I
charge
/10 I
charge
. The new charge to discharge
ratio will be:
% Deadtime
Iadditional
10 (Icharge)
Icharge
A bidirectional clock pin is provided for synchronization
or for master/slave operation. As a master, the clock pin
provides a positive output pulse during the discharge of C
T
.
As a slave, the clock pin is an input that resets the PWM latch
and blanks the drive output, but does not discharge C
T
.
Therefore, the oscillator is not synchronized by driving the
clock pin alone. Figures 28, 29 and 30 provide suggested
synchronization.
Error Amplifier
A fully compensated Error Amplifier is provided. It
features a typical DC voltage gain of 95 dB and a gain
bandwidth product of 8.3 MHz with 75 degrees of phase
margin (Figure 4). Typical application circuits will have the
noninverting input tied to the reference. The inverting input
will typically be connected to a feedback voltage generated
from the output of the switching power supply. Both inputs
have a common mode voltage (V
CM
) input range of 1.5 V to
5.5 V. The Error Amplifier Output is provided for external
loop compensation.
SoftStart Latch
SoftStart is accomplished in conjunction with an
external capacitor. The SoftStart capacitor is charged by an
internal 9.0 A current source. This capacitor clamps the
output of the error amplifier to less than its normal output
voltage, thus limiting the duty cycle. The time it takes for a
capacitor to reach full charge is given by:
(4.5
105) CSoft-Start
A SoftStart latch is incorporated to prevent erratic
operation of this circuitry. Two conditions can cause the
SoftStart circuit to latch so that the SoftStart capacitor
stays discharged. The first condition is activation of an
undervoltage lockout of either V
CC
or V
ref
. The second
condition is when current sense input exceeds 1.4 V. Since
this latch is “set dominant”, it cannot be reset until either of
these signals is removed and, the voltage at C
SoftStart
is less
than 0.5 V.
t
PWM Comparator and Latch
A PWM circuit typically compares an error voltage with
a ramp signal. The outcome of this comparison determines
the state of the output. In voltage mode operation the ramp
signal is the voltage ramp of the timing capacitor. In current
mode operation the ramp signal is the voltage ramp induced
in a current sensing element. The ramp input of the PWM
comparator is pinned out so that the user can decide which
mode of operation best suits the application requirements.
The ramp input has a 1.25 V offset such that whenever the
voltage at this pin exceeds the error amplifier output voltage
minus 1.25 V, the PWM comparator will cause the PWM
latch to set, disabling the outputs. Once the PWM latch is set,
only a blanking pulse by the oscillator can reset it, thus
initiating the next cycle.
Current Limiting and Shutdown
A pin is provided to perform current limiting and
shutdown operations. Two comparators are connected to the
input of this pin. The reference voltage for the current limit
comparator is not set internally. A pin is provided so the user
can set the voltage. When the voltage at the current limit
input pin exceeds the externally set voltage, the PWM latch
is set, disabling the output. In this way cyclebycycle
current limiting is accomplished. If a current limit resistor is
used in series with the power devices, the value of the
resistor is found by:
RSense
ILimit Reference Voltage
Ipk (switch)
If the voltage at this pin exceeds 1.4 V, the second
comparator is activated. This comparator sets a latch which,
in turn, causes the soft start capacitor to be discharged. In this
way a “hiccup” mode of recovery is possible in the case of
output short circuits. If a current limit resistor is used in
series with the output devices, the peak current at which the
controller will enter a “hiccup” mode is given by:
Ishutdown
1.4 V
RSense
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MC33023DWR2 | High Speed Single−Ended PWM Controller |
| MC33023DWR2G | High Speed Single−Ended PWM Controller |
| MC33025DWG | High Speed Double−Ended PWM Controller |
| MC33025DWR2 | High Speed Double−Ended PWM Controller |
| MC33025DWR2G | High Speed Double−Ended PWM Controller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MC33023DWR2 | 功能描述:電流型 PWM 控制器 Single Ended Voltage RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MC33023DWR2G | 功能描述:電流型 PWM 控制器 Single Ended Voltage or Current Mode PWM RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MC33023P | 制造商:Motorola 功能描述:MOTOROLA S1I2F |
| MC33024 | 制造商:SPC Multicomp 功能描述:FINGER GUARD 制造商:SPC Multicomp 功能描述:FINGER GUARD; For Use With:127mm Axial Fans; Fan Size:127mm; Fixing Centers:113.3mm; Guard Material:Steel; Accessory Type:Finger Guard; Color:Chrome; External Depth:5.5mm; External Height:115.6mm; External Width:115.6mm ;RoHS Compliant: Yes |
| MC33025 | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:High Speed Double-Ended PWM Controller |
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