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參數資料
| 型號： | MC44605 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | High Safety, Latched Mode, GreenLine PWM Controller for (Multi)Synchronized Applications |
| 中文描述： | 高安全性，鎖存模式，二七二三六七六七的PWM控制器（同步多應用） |
| 文件頁數： | 9/20頁 |
| 文件大小： | 328K |
| 代理商： | MC44605 |
MC44605
http://onsemi.com
9
The Error Amp Output (Pin 13) is provided for external
loop compensation. The output voltage is offset by two
diodes drops (
1.4 V) and divided by three before it
connects to the inverting input of the Current Sense
Comparator. This guarantees that no drive pulses appear at
the Source Output (Pin 3) when Pin 13 is at its lowest state
(VOL). This occurs when the power supply is operating and
the load is removed, or at the beginning of a soft–start
interval. The Error Amp minimum feedback resistance is
limited by the amplifier’s minimum source current (0.2 mA)
and the required output voltage (VOH) to reach the current
sense comparator’s 1.0 V clamp level:
R1(min)
(3
1 V)
0.2 mA
1.4 V
22 k
Current Sense Comparator and PWM Latch
The MC44605 operates as a current mode controller. The
circuit uses a current sense comparator to compare the
inductor current to the threshold level established by the
Error Amplifier output (Pin 13). When the current reaches
the threshold, the current sense comparator terminates the
output switch conduction that has been initiated by the
oscillator, by resetting the PWM Latch. Thus the error signal
controls the peak inductor current on a cycle–by–cycle
basis. This configuration ensures that only one single pulse
appears at the Source Output during the appropriate
oscillator cycle.
Figure 2. Output Totem Pole
R
S
Q
UVLO
Disout
Vdemag out
Thermal
Protection
PWM
Latch
Current Sense
Comparator
Substrate
Current
Sense
14
3
7
C
RS
R
R3
Q1
Vin
VC
R2
VS
The inductor current is converted to a voltage by inserting
the ground referenced sense resistor RS in series with the
power switch Q1.
This voltage is monitored by the Current Sense Input
(Pin 7) and compared to a level derived from the Error Amp
output. The peak inductor current under normal operating
conditions is controlled by the voltage at Pin 13 where:
Ipk
V(pin13)
1.4 V
3
RS
The Current Sense Comparator threshold is internally
clamped to 1.0 V. Therefore the maximum peak switch
current is:
Ipk(max)
1 V
RS
Undervoltage Lockout Section
As depicted in Figure 3, an undervoltage lockout has been
incorporated to guarantee that the IC is fully functional
before allowing the system working.
In effect, the VCC is connected to the non inverting input
of a comparator that has an upper threshold equal to 14,5 V
(typical Vstup–th) and a lower one equal to 7.5 V (typical
Vdisable 2). This hysteresis comparator enables or disables
the reference block that generates the voltage and current
sources required by the system.
This block particularly, produces Vref (pin 16 voltage) and
Iref that is determined by the resistor Rref connected between
pin 16 and the ground:
Iref
Vref
Rref
where Vref
2.5 V (typically)
Figure 3. VCC Management
Reference Block:
Voltage and Current
Sources Generator
(Vref, Iref, ...)
Vref enable
CSTART–UP
1
0
1
0
Vdisable
7.5 V
START–UP
14.5 V
UVLO1
(to SOFTSTART)
Vdisable1
9.0 V
CUVLO1
Rref
Pin 16
MC44605
VCC
(Pin 1)
In addition to this, VCC is compared to a second threshold
level that is nearly equal to 9 V (Vdisable1) so that a signal
UVLO1 is generated to reset the soft start block and so, to
disable the output stage (refer to the Soft–Start §) as soon as
VCC becomes lower than Vdisable 1. In this way, the circuit
is reset and made ready for a next start–up, before the
reference block is disabled (refer to Figure 3). Thus, finally
the upper limit for the minimum normal operating voltage
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相關代理商/技術參數 |
參數描述 |
|---|---|
| MC44605_06 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:High Safety, Latched Mode, GreenLine TM PWM Controller for (Multi) Synchronized Applications |
| MC44605P | 功能描述:電流型 PWM 控制器 Greenline PWM RoHS:否 制造商:Texas Instruments 開關頻率: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 輸出端數量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MC44605PG | 功能描述:電流型 PWM 控制器 ANA SMPS PWM FREQ CONT RoHS:否 制造商:Texas Instruments 開關頻率: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 輸出端數量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| MC44608 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Few External Components Reliable Flexible GreenLine Very High Voltage PWM Controller |
| MC44608_06 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Few External Components Reliable and Flexible SMPS Controller |
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