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參數(shù)資料
| 型號： | LM5027AMHX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | TSSOP-20 |
| 文件頁數(shù)： | 9/28頁 |
| 文件大小： | 561K |
| 代理商： | LM5027AMHX |
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TABLE 1. Fault/Event Summary
Fault/Event
Vcc
UVLO
OTP
SS
SSSR
OUTA
OUTB
OUTSR
UVLO<0.4V
>6.2V
-
>1.25V
Fast
discharge
Fast
discharge
Low
2.0V<UVLO
>0.4V
>6.2V
-
>1.25V
Fast
discharge
after
SSSR<2V
Slow
discharge
Low
SS< 1V
>6.2V
>2.0V
>1.25V
-
Fast
discharge
Low
SSSR <2.0V
>6.2V
>2.0V
>1.25V
>4.0V
-
Switching
Low
OTP
<1.25V
>6.2V
>2.0V
-
Fast
discharge
after
SSSR<2V
Slow
discharge
Low
PWM Comparators
The pulse width modulator (PWM) comparator compares the
voltage ramp signal at the RAMP pin to the loop error signal.
The loop error signal is received from the external feedback
and isolation circuit in the form of a control current into the
matched pair of NPN transistors which sink current through a
5 k
resistor connected to the 5V reference. The resulting
control voltage is compared at the PWM input to a 1V level
shifted ramp signal. An opto-coupler detector can be con-
nected directly between the REF pin and the COMP pin. Since
the COMP pin is a current mirror input, the potential difference
across the opto-coupler detector is nearly constant. The
bandwidth limiting phase delay which is normally introduced
by the significant capacitance of the opto-coupler is thereby
greatly reduced. Higher loop bandwidths can be realized
since the bandwidth-limiting pole associated with the opto-
coupler is now at a much higher frequency. The PWM com-
parator polarity is configured such that with no current into the
COMP pin, the controller produces maximum duty cycle at the
main gate drive output (OUTA).
Feed-Forward Ramp
An external resistor (R
FF) and capacitor (CFF) connected to
VIN, AGND, and the RAMP pins is required to create the
PWM ramp signal as shown in Figure 8. The slope of the sig-
nal at the RAMP pin will vary in proportion to the input line
voltage. This varying slope provides line feed-forward infor-
mation necessary to improve line transient response with
voltage mode control. The RAMP signal is compared to the
error signal by the pulse width modulator comparator to con-
trol the duty cycle of the outputs. With a constant error signal,
the on-time (t
ON) varies inversely with the input voltage (VIN)
to stabilize the volt-second product of the transformer prima-
ry. The power path gain of the conventional voltage-mode
pulse with modulator (oscillator generated ramp) varies di-
rectly with input voltage. The use of a line generated ramp
(input voltage feed-forward) nearly eliminates the gain varia-
tion. As a result, the feedback loop is only required to make
very small corrections for large changes in input voltage. At
the end of each clock period, an internal MOSFET with an
R
DS(ON) of 10 (typical) is enabled to reset the CFF capacitor
voltage to ground.
17
www.national.com
LM5027A
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相關代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM5027AMHX/NOPB | 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| LM5027ASQ/NOPB | 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| LM5027ASQX/NOPB | 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| LM5027MH | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Voltage Mode Active Clamp Controller |
| LM5027MH/NOPB | 功能描述:電壓模式 PWM 控制器 Voltage Mode Active Clamp Controller RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
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