SC418
6
FB Ripple
Voltage (V
FB
)
FB threshold
(500mV)
Inductor
Current
DH
DL
(0A)
minimum frequency
After the programmable time-out, DL drives
high if V
FB
has not reached the FB threshold.
DH On-time is triggered when
V
FB
reaches the FB Threshold
On-time
(T
ON
)
programmable time-out
Figure 5 Ultrasonic Power-Save Operation
The equation for determining the R
PSV
resistor value is
shown next. The desired minimum frequency is f
SWMIN
.
SWMIN
PSV
f
pF
350
1
R
Power-Save Mode Operation
The device provides power-save operation at light loads
with no minimum operating frequency, selected by float-
ing the PSV pin (no connection). In this mode of opera-
tion, the zero cross comparator monitors inductor current
via the voltage across the low-side MOSFET during the
off-time. If the inductor current falls to zero for 8 consecu-
tive switching cycles, the controller enters power-save
operation. It will then turn off the low-side MOSFET on
each subsequent cycle, provided that the current crosses
zero. After the low-side MOSFET is off, both high-side and
low-sides MOSFETs remain off until V
FB
drops to the 500mV
threshold. While the MOSFETs are off the load is supplied
by the output capacitor. If the inductor current does not
reach zero on any switching cycle, the controller immedi-
ately exits power-save and returns to forced continuous
mode. Figure 6 shows power-save operation at light
loads.
FB Ripple
Voltage
(V
FB
)
FB threshold
DL
DH
Inductor
Current
Zero (0A)
DH On-time is triggered when
V
FB
reaches the FB Threshold.
(500mV)
On-time (T
ON
)
DL drives high when on-time is completed.
DL remains high until inductor current reaches zero.
Dead time varies
according to load
Figure 6 Power-Save Operation
Smart Power-Save Protection
Active loads may leak current from a higher voltage into
the switcher output. Under light load conditions with
power-save enabled, this can force V
OUT
to slowly rise and
reach the over-voltage threshold, resulting in a hard shut-
down. Smart power-save prevents this condition. When
the FB voltage exceeds 0% above nominal (exceeds
550mV), the device immediately disables power-save and
DL drives high to turn on the low-side MOSFET. This draws
current from V
OUT
through the inductor and causes V
OUT
to
fall. When V
FB
drops back to the 500mV trip point, a normal
T
ON
switching cycle begins. This method prevents a hard
OVP shutdown and cycles energy from V
OUT
back to V
IN
. It
also minimizes operating power by avoiding forced con-
duction mode operation. Figure 7 shows typical wave-
forms for the Smart Power-save feature.
Applications Information (continued)
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
SC424MLTRT
IC REG DL BUCK/LINEAR 28MLPQ
SC4250LISTRT
IC HOT SWAP CTRLR 8-SOIC
SC427MLTRT
IC REG DL BUCK/LINEAR 32MLPQ
SE95D,112
IC SENSOR TEMP 2.8-5.5V SOT96-1
SE97BTP,547
IC TEMP SENSOR DIMM 8HWSON
SE98ATP,547
IC TEMP SENSOR DDR 8-HWSON
SG6901ASZ
IC PFC CTLR AVERAGE CURR 20SOIC
SG6932SZ
IC PFC CONTROLLER CCM 16SOP
相关代理商/技术参数
SC419
制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:EcoSpeedTM DC-DC Converter with Integrated Boost Diode
SC419970CGCR2
制造商:Motorola Inc 功能描述:
SC419EVB
制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:EcoSpeedTM DC-DC Converter with Integrated Boost Diode
SC419ULTRT
功能描述:IC REG CTRLR BUCK PWM 20-MLPQ RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:EcoSpeed®, SmartDrive™ 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR
SC41E6
制造商:INFINEON 制造商全称:Infineon Technologies AG 功能描述:SIEMENS ANNOUNCES A SUB-MICTON GENERATION OF CHANNELLESS GATE-ARRAYS BASED ON THE PROVEN MEGALOGIC PROCESS
SC4-2 24VDC
制造商:PEPPERL+FUCHS 功能描述:Sensor, Machine Safety, Control Unit, 24VDC, 2 Channel, LED Display, 117230
SC420
功能描述:UPS - 不间断电源 420VA/260W 4 Outlet
RoHS:否 制造商:Phoenix Contact 功率额定值: 输出电压额定值:24 V 出口数量:2 运行时间（满载）: 运行时间（半载）:
SC4201
制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Multi-Phase Link Controller