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參數(shù)資料
| 型號(hào)： | NCP1562A |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | High Performance Active Active Clamp/Reset PWM Controller Controller(高性能有效Clamp/Reset PWM控制器) |
| 中文描述： | 高性能主動(dòng)有源鉗位/復(fù)位PWM控制器控制器（高性能有效鉗位/復(fù)位的PWM控制器） |
| 文件頁(yè)數(shù)： | 21/26頁(yè) |
| 文件大小： | 277K |
| 代理商： | NCP1562A |
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NCP1562A, NCP1562B
http://onsemi.com
21
The output overlap delay is adjusted by connecting a
resistor, R
D
, from the t
D
pin to ground
.
The overlap delay
is proportional to R
D
. A minimum delay of 20 ns is
obtained by grounding the t
D
pin.
The leading delay is purposely made longer than the
trailing delay. This allows the user to optimize the delay for
the turn on transition of the main switch and ensures the
active clamp switch always exhibits zero volt switching.
Analog and Power Ground (PGND)
The NCP1562 has an analog ground, GND, and a power
ground, PGND, terminal. GND is used for analog
connections such as V
REF
, R
T
C
T
, feedforward among
others. PGND is used for high current connections such as
the internal output drivers. It is recommended to have
independent analog and power ground planes and connect
them at a single point, preferably at the ground terminal of
the system. This will prevent high current flowing on
PGND from injecting noise in GND. The PGND
connection should be as short and wide as possible to
reduce inductance-induced spikes.
Oscillator
The oscillator frequency and maximum duty cycle are
set by an R
T
C
T
divider from V
REF
as shown in Figure 48.
A 500 A current source (I
RTCT
) discharges the timing
capacitor (C
T
) upon reaching its peak threshold
(V
RTCT(peak)
), typically 3.0 V. Once C
T
reaches its valley
voltage (V
RTCT(valley)
), typically 2.0 V, I
RTCT
turns OFF
allowing C
T
to charge back up through R
T
. The resulting
waveform on the RTCT pin has a sawtooth like shape.
Enable
I
RTCT
V
REF
RTCT
R
T
C
T
3 V
2 V
Figure 48. Oscillator Configuration
OUT2 is set high once V
RTCT(valley)
is reached, followed
by OUT1 delayed by the overlap delay. Once V
RTCT(peak)
is reached, OUT1 goes low, followed by OUT2 delayed by
t
D
.
The duty cycle is the C
T
charge time (t
RTCT(C)
) minus the
overlap delay over the total charge and discharge (t
RTCT(D)
)
times. The charge and discharge times are calculated using
Equations 5 and 6. However, these equations are an
approximation as they do not take into account the
propagation delays of the internal comparator.
tRTCT(C)
RTCT
ln
VRTCT(valley)-VREF
VRTCT(peak)-VREF
(eq. 5)
tRTCT(D)
RTCT
ln
(IRTCT
(IRTCT
RT)
RT)
VRTCT(peak)-VREF
VRTCT(valley)-VREF
(eq. 6)
The duty cycle, D, is given by Equation 7.
D
tRTCT(C)-tD
tRTCT(C)
tRTCT(D)
(eq. 7)
Substituting Equations 5, 6, and 7, and after a little
algebraic manipulation and replacing values, it simplifies
to:
D
ln
VRTCT(valley)-VREF
VRTCT(peak)-VREF
-
tD
RTCT
ln
VRTCT(valley)-VREF
VRTCT(peak)-VREF
(IRTCT
RT)
VRTCT(peak)-VREF
(IRTCT
RT)
VRTCT(valley)-VREF
(eq. 8)
It can be observed that D is set by R
T
, C
T
and t
D
. This
equation has two variables and can be solved iteratively. In
general, the time delay is a small portion of the ON time and
can be ignored as a first approximation. R
T
is then selected
to achieve a given duty cycle. Once the R
T
is selected, C
T
is chosen to obtain the desired operating frequency using
Equation 9.
f
1
RTCT
ln
VRTCT(valley)-VREF
VRTCT(peak)-VREF
(IRTCT
RT)
VRTCT(peak)-VREF
(IRTCT
RT)
VRTCT(valley)-VREF
(eq. 9)
Figures 23 through 26 show the frequency and duty cycle
variation vs R
T
for several C
T
values. R
T
should not be less
than 6.0 k . Otherwise, the R
T
C
T
charge current will
exceed the pulldown current and the oscillator will be in an
undefined state.
Synchronization
A proprietary bidirectional frequency synchronization
architecture allows multiple NCP1562 to synchronize in a
master-slave configuration. It can synchronize to
frequencies above or below the free running frequency.
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| NCP1562A WAF | 制造商:ON Semiconductor 功能描述: |
| NCP1562ADBR2G | 功能描述:電壓模式 PWM 控制器 HI PERF RESET PWM CONTLR RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)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 |
| NCP1562ADR2G | 功能描述:電壓模式 PWM 控制器 HI PERF RESET PWM CONTLR RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)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 |
| NCP1562BDBR2G | 功能描述:電壓模式 PWM 控制器 HI PERF RESET PWM CONTLR RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)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 |
| NCP1562BDR2G | 功能描述:電壓模式 PWM 控制器 HI PERF RESET PWM CONTLR RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)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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