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| 型号： | LTC3809EDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 10-DFN |
| 标准包装： | 121 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 825kHz |
| 占空比： | 100% |
| 电源电压： | 2.75 V ~ 9.8 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： | -40°C ~ 85°C |
| 封装/外壳： | 10-WFDFN 裸露焊盘 |
| 包装： | 管件 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
LTC3809
APPLICATIONS INFORMATION
2.0
Top P-Channel Duty Cycle =
V OUT
V IN
1.5
Bottom N-Channel Duty Cycle =
V IN – V OUT
V IN
1.0
The MOSFET power dissipations at maximum output
0.5
current are:
? I OUT ( MAX ) 2 ? ρ T DS ( ON ) + 2 ? V IN 2
V OUT
0
–50
0 50 100
JUNCTION TEMPERATURE (°C)
150
P TOP =
V IN
? I OUT ( MAX ) ? C RSS ? f
? R
3809 F02
Figure 2. R DS(ON) vs Temperature
P BOT =
V IN – V OUT
V IN
? I OUT ( MAX ) 2 ? ρ T ? R DS ( ON )
short-circuit current sense threshold Δ V SC is set approxi-
mately 90mV when IPRG is ?oating (60mV when IPRG is
tied low; 150mV when IPRG is tied high). The on-resistance
of N-channel MOSFET is determined by:
Both MOSFETs have I 2 R losses and the P TOP 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
R DS ( ON ) MAX =
Δ V SC
I SC ( PEAK )
when the bottom duty cycle is 100%.
The LTC3809 utilizes a non-overlapping, anti-shoot-
through gate drive control scheme to ensure that the
< R DS ( ON ) <
Theshort-circuitcurrentlimit(I SC(PEAK) )shouldbelarger
than the I OUT(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, I SC(PEAK) should be
smaller than the minimum value of their current ratings.
A reasonable range is:
I OUT(MAX) < I SC(PEAK) < I RATING(MIN)
Therefore, the on-resistance of N-channel MOSFET should
be chosen within the following range:
Δ V SC Δ V SC
I RATING ( MIN ) I OUT ( MAX )
where Δ V SC is 90mV, 60mV or 150mV with IPRG being
?oated, tied to GND or V IN 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:
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-channel
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 (Q G )
less than 25nC to 30nC (at 4.5V GS ) and a turn-off delay
(t D(OFF) ) of less than approximately 140ns. However, due
to differences in test and speci?cation methods of various
MOSFET manufacturers, and in the variations in Q G and
t D(OFF) with gate drive (V IN ) 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 increases,
if the input supply current increases dramatically, then the
likely cause is shoot-through. Note that some MOSFETs
3809fc
13
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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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