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参数资料
| 型号： | LTC3809EMS |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, 825 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封装： | PLASTIC, MSOP-10 |
| 文件页数： | 5/24页 |
| 文件大小： | 266K |
| 代理商： | LTC3809EMS |
13
LTC3809
3809f
short-circuit current sense threshold
VSC is set approxi-
mately 90mV when IPRG is floating (60mV when IPRG is
tied low; 150mV when IPRG is tied high). The on-resis-
tance of N-channel MOSFET is determined by:
R
V
I
DS ON MAX
SC
SC PEAK
()
=
The short-circuit current limit (ISC(PEAK)) should be larger
than the IOUT(MAX) with some margin to avoid interfering
with the peak current sensing loop. On the other hand, in
order to prevent the MOSFETs from excessive heating and
the inductor from saturation, ISC(PEAK) should be smaller
than the minimum value of their current ratings. A reason-
able range is:
IOUT(MAX) < ISC(PEAK) < IRATING(MIN)
Therefore, the on-resistance of N-channel MOSFET should
be chosen within the following range:
<<
V
I
R
V
I
SC
RATING MIN
DS ON
SC
OUT MAX
()
where
VSC is 90mV, 60mV or 150mV with IPRG being
floated, tied to GND or VIN respectively.
The power dissipated in the MOSFET strongly depends on
its respective duty cycles and load current. When the
LTC3809 is operating in continuous mode, the duty cycles
for the MOSFETs are:
Top P-Channel Duty Cycle =
Bottom N-Channel Duty Cycle =
V
VV
V
OUT
IN
OUT
IN
–
The MOSFET power dissipations at maximum output
current are:
P
V
IR
V
IC
f
P
VV
V
IR
TOP
OUT
IN
OUT MAX
T
DS ON
IN
OUT MAX
RSS
BOT
IN
OUT
IN
OUT MAX
T
DS ON
=+
=
–
()
(
)
()
(
)
22
2
ρ
Both MOSFETs have I2R losses and the PTOP equation
includes an additional term for transition losses, which are
largest at high input voltages. The bottom MOSFET losses
are greatest at high input voltage or during a short-circuit
when the bottom duty cycle is 100%.
The LTC3809 utilizes a non-overlapping, anti-shoot-
through gate drive control scheme to ensure that the P-
and N-channel MOSFETs are not turned on at the same
time. To function properly, the control scheme requires
that the MOSFETs used are intended for DC/DC switching
applications. Many power MOSFETs, particularly P-chan-
nel MOSFETs, are intended to be used as static switches
and therefore are slow to turn on or off.
Reasonable starting criteria for selecting the P-channel
MOSFET are that it must typically have a gate charge (QG)
less than 25nC to 30nC (at 4.5VGS) and a turn-off delay
(tD(OFF)) of less than approximately 140ns. However, due
to differences in test and specification methods of various
MOSFET manufacturers, and in the variations in QG and
tD(OFF) with gate drive (VIN) voltage, the P-channel MOSFET
ultimately should be evaluated in the actual LTC3809
application circuit to ensure proper operation.
Shoot-through between the P-channel and N-channel
MOSFETs can most easily be spotted by monitoring the
input supply current. As the input supply voltage in-
creases, if the input supply current increases dramatically,
then the likely cause is shoot-through. Note that some
JUNCTION TEMPERATURE (
°C)
–50
ρ
TNORMALIZED
ON
RESISTANCE
1.0
1.5
150
3809 F02
0.5
0
50
100
2.0
Figure 2. RDS(ON) vs Temperature
APPLICATIO S I FOR ATIO
WU
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相关代理商/技术参数 |
参数描述 |
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| LTC3809EMSE | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3809EMSE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3809EMSE#TR | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3809EMSE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3809EMSE-1 | 功能描述:IC REG CTRLR BUCK PWM CM 10-MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
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