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参数资料
| 型号： | LTC3809IDD-1 |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, 600 kHz SWITCHING FREQ-MAX, PQCC10 |
| 封装： | 3 X 3 MM, PLASTIC, DFN-10 |
| 文件页数： | 6/24页 |
| 文件大小： | 256K |
| 代理商： | LTC3809IDD-1 |
LTC3809-1
14
38091fc
that do not work well at high input voltages (e.g., VIN >
5V) may work ne at lower voltages (e.g., 3.3V).
Selecting the N-channel MOSFET is typically easier, since
for a given RDS(ON),thegatechargeandturn-onandturn-off
delays are much smaller than for a P-channel MOSFET.
Inductor Value Calculation
Given the desired input and output voltages, the inductor
value and operating frequency, fOSC, directly determine
the inductor’s peak-to-peak ripple current:
I
V
VV
fL
RIPPLE
OUT
IN
OUT
OSC
=
–
Lower ripple current reduces core losses in the inductor,
ESR losses in the output capacitors and output voltage
ripple. Thus, highest efciency operation is obtained at
low frequency with a small ripple current. Achieving this,
however, requires a large inductor.
A reasonable starting point is to choose a ripple current
that is about 40% of IOUT(MAX). Note that the largest ripple
current occurs at the highest input voltage. To guarantee
that ripple current does not exceed a specied maximum,
the inductor should be chosen according to:
L
VV
fI
V
IN
OUT
OSC
RIPPLE
OUT
IN
≥
–
Burst Mode Operation Considerations
The choice of RDS(ON) and inductor value also determines
the load current at which the LTC3809-1 enters Burst Mode
operation. When bursting, the controller clamps the peak
inductor current to approximately:
I
V
R
BURST PEAK
SENSE MAX
DS ON
()
=
Δ
1
4
APPLICATIONS INFORMATION
The corresponding average current depends on the
amount of ripple current. Lower inductor values (higher
IRIPPLE) will reduce the load current at which Burst Mode
operation begins.
The ripple current is normally set so that the inductor current
is continuous during the burst periods. Therefore,
IRIPPLE ≤ IBURST(PEAK)
This implies a minimum inductance of:
L
VV
fI
V
MIN
IN
OUT
OSC
BURST PEAK
OUT
IN
≤
–
()
A smaller value than LMIN could be used in the circuit,
although the inductor current will not be continuous
during burst periods, which will result in slightly lower
efciency. In general, though, it is a good idea to keep
IRIPPLE comparable to IBURST(PEAK).
Inductor Core Selection
Once the value of L is known, the type of inductor must be
selected. Actual core loss is independent of core size for a
xed inductor value, but is very dependent on the induc-
tance selected. As inductance increases, core losses go
down. Unfortunately, increased inductance requires more
turns of wire and therefore copper losses will increase.
Ferrite designs have very low core losses and are pre-
ferred at high switching frequencies, so design goals can
concentrate on copper loss and preventing saturation.
Ferrite core material saturates “hard”, which means that
inductance collapses abruptly when the peak design current
is exceeded. Core saturation results in an abrupt increase
in inductor ripple current and consequent output voltage
ripple. Do not allow the core to saturate!
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| LTC3809IDD-1#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 10-DFN 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) |
| LTC3809IDD-1#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 10-DFN 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) |
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| LTC3809IMSE-1#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) |
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