SC418
9
cycle. The switcher will shut off if VDDA falls below 2.7V.
VDDP does not have ULVO protection.
Note that the VDDA UVLO will not stop MOSFET switching
until the VDDA voltage falls to 2.7V. During this time the
gate driver voltages will track the VDDA supply. Not all
MOSFETs will operate or switch effectively at drive levels
of 2.7V. For this reason, it is not recommended to rely on
VDDA UVLO to shutdown the switcher unless the MOSFETs
are capable of operating with 2.7V drive.
LDO Regulator
The LDO output is programmable from 0.75V to 5.25V
using external resistors. The feedback pin (FBL) for the
LDO is regulated to 750mV. The LDO enable pin (ENL)
provides independent control. The LDO voltage can be
used to provide the bias voltage for the switching regula-
tor. When a separate source is used as the bias supply, the
LDO can be programmed to provide a different voltage.
The external resistor connections are shown in Figure 0.
VLDO
To FBL pin
R
LDO2
R
LDO1
Figure 10 VLDO Resistor Divider
The LDO output voltage is set by the following equation.
2
LDO
1
LDO
R
R
1
mV
750
VLDO
A minimum capacitance of 糉 referenced to AGND is
normally required at the output of the LDO for stability. If
the LDO is providing bias power to the device, then a
minimum 0.糉 capacitor referenced to AGND is required,
along with a minimum 糉 capacitor referenced to PGND
to filter the gate drive pulses. Refer to the PCB Layout
Guidelines section.
ENL Pin and VIN UVLO
The ENL pin also acts as the V
IN
under-voltage lockout for
the switcher. The V
IN
UVLO voltage is programmable via a
resistor divider at the VIN, ENL and AGND pins. The V
IN
UVLO function has a typical threshold of 2.6V on the V
IN
rising edge. The falling edge threshold is 2.4V.
Timing is important when driving ENL with logic and not
implementing V
IN
UVLO. The ENL pin must transition from
high to low within 2 switching cycles to avoid the PWM
output turning off. If ENL goes below the V
IN
UVLO thresh-
old and stays above V, then the switcher will turn off but
the LDO will remain on.
Note that it is possible to operate the switcher with the
LDO disabled, but the ENL pin must be below the logic
low threshold (0.4V maximum), otherwise the V
IN
UVLO
function will disable the switcher.
The table below summarizes the function of the ENL and
EN pins, with respect to the rising edge of ENL.
EN
ENL LDO status Switcher status
low low, < 0.4V off
off
high low, < 0.4V off
on
low high, < 2.6V on
off
high high, < 2.6V on
off
low high, > 2.6V on
off
high high, > 2.6V on
on
Figure shows the ENL voltage thresholds and their
effect on LDO and Switcher operation.
AGND
ENL low
threshold
(min 0.4V)
2.6V
2.4V
LDO on
LDO on
LDO off
VIN UVLO hysteresis
ENL voltage
Switcher on if EN = high
Switcher on if EN = high
Switcher off by VIN UVLO
Figure 11 ENL Thresholds
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