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參數(shù)資料
| 型號： | SC403MLTRT |
| 廠商： | Semtech |
| 文件頁數(shù)： | 18/32頁 |
| 文件大?。?/td> | 741K |
| 描述： | IC REG DL BCK/LINEAR SYNC 32MLPQ |
| 標準包裝： | 1 |
| 系列： | EcoSpeed®, SmartDrive™ |
| 拓撲： | 降壓（降壓）同步（1），線性（LDO）（1） |
| 功能： | 任何功能 |
| 輸出數(shù)： | 2 |
| 頻率 - 開關： | 1MHz |
| 電壓/電流 - 輸出 1： | 可調(diào)至 0.75V，6A |
| 電壓/電流 - 輸出 2： | 可調(diào)至 0.75V，200mA |
| 帶 LED 驅(qū)動器： | 無 |
| 帶監(jiān)控器： | 無 |
| 帶序列發(fā)生器： | 是 |
| 電源電壓： | 3 V ~ 28 V |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 32-VFQFN 裸露焊盤 |
| 供應商設備封裝： | 32-MLPQ（5x5） |
| 包裝： | 標準包裝 |
| 其它名稱： | SC403MLDKR |
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SC403
18
Because the on-times are forced to occur at intervals no
greater than 40祍, the frequency will not fall below
~25kHz. Figure 5 shows ultrasonic PSAVE operation.
FB Ripple
Voltage
(V
FB
)
FB threshold
(750mV)
Inductor
Current
(0A)
Minimum f
SW
~ 20kHz
DH
DH On-Time is triggered when
V
FB
reaches the FB Threshold
On-time
(T
ON
)
DL
50祍ec time-out
After the 50祍ec time-out, DL drives high if V
FB
has not reached the FB threshold.
Figure 5 Ultrasonic PSAVE Operation
Smart PSAVE Protection
Active loads may leak current from a higher voltage into
the switcher output. Under light load conditions with
PSAVE enabled, this can force V
OUT
to slowly rise and reach
the over-voltage threshold, resulting in a hard shutdown.
Smart PSAVE prevents this condition. When the FB voltage
exceeds 10% above nominal, the device immediately dis-
ables PSAVE, and DL drives high to turn on the low-side
MOSFET. This draws current from V
OUT
through the induc-
tor and causes V
OUT
to fall. When V
FB
drops back to the
750mV trip point, a normal t
ON
switching cycle begins. This
method prevents a hard OVP shutdown and also cycles
energy from V
OUT
back to V
IN
. It also minimizes operating
power by avoiding forced conduction mode operation.
Figure 6 shows typical waveforms for the Smart PSAVE
feature.
FB
threshold
High-side
Drive (DH)
Low-side
Drive (DL)
V
OUT
drifts up to due to leakage
current flowing into C
OUT
DH and DL off
DL turns on when Smart
PSAVE threshold is reached
Smart Power Save
Threshold (825mV)
DL turns off when FB
Single DH on-time pulse
after DL turn-off
V
OUT
discharges via inductor
and low-side MOSFET
Normal DL pulse after
DH on-time pulse
Normal V
OUT
ripple
Figure 6 Smart PSAVE
SmartDrive
TM
For each DH pulse the DH driver initially turns on the high-
side MOSFET at a lower speed, allowing a softer, smooth
turn-off of the low-side diode. Once the diode is off and
the LX voltage has risen 1V above PGND, the SmartDrive
circuit automatically drives the high-side MOSFET on at a
rapid rate. This technique reduces switching power loss
while maintaining high efficiency and also avoids the
need for snubbers or series resistors in the gate drive.
Current Limit Protection
Programmable current limiting is accomplished by using
the RDS
ON
of the lower MOSFET for current sensing. The
current limit is set by the R
ILIM
resistor. The R
ILIM
resistor con-
nects from the ILIM pin to the LXS pin which is also the drain
of the low-side MOSFET. When the low-side MOSFET is on,
an internal ~10糀 current flows from the ILIM pin and
through the R
ILIM
resistor, creating a voltage drop across the
resistor. While the low-side MOSFET is on, the inductor
current flows through it and creates a voltage across the
RDS
ON
. The voltage across the MOSFET is negative with
respect to ground. If this MOSFET voltage drop exceeds the
voltage across R
ILIM
, the voltage at the ILIM pin will be nega-
tive and current limit will activate. The current limit then
keeps the low-side MOSFET on and will not allow another
high-side on-time, until the current in the low-side MOSFET
reduces enough to bring the ILIM voltage back up to zero.
This method regulates the inductor valley current at the
level shown by ILIM in Figure 7.
Applications Information (continued)
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| SC4040 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:PRECISION SHUNT VOLTAGE REFERENCE |
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| SC4040ASK | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:PRECISION SHUNT VOLTAGE REFERENCE |
| SC4040ASK.TR | 制造商:Semtech Corporation 功能描述:IC V-REF PRECISION 2.5V 3SOT-23 T/R |
| SC4040AZ | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:PRECISION SHUNT VOLTAGE REFERENCE |
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