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參數(shù)資料
| 型號(hào)： | L6997 |
| 廠商： | 意法半導(dǎo)體 |
| 英文描述： | STEP DOWN CONTROLLER FOR LOW VOLTAGE OPERATIONS |
| 中文描述： | 降壓控制器低電壓運(yùn)作 |
| 文件頁數(shù)： | 10/23頁 |
| 文件大?。?/td> | 291K |
| 代理商： | L6997 |
L6997
10/23
be supposed linear function of the time.
Eq 8
so the output voltage is given by:
Eq 9
calling V
out
as the V
out
final value, the output charging time can be estimated as:
Eq 10
the minimum C
SS
value is given imposing this condition:
Eq 11
T
out
=T
uvp
1.5 Current limit
The current limit comparator senses the inductor current through the low side MOSFET RDS
ON
drop and com-
pares this value with the ILIM pin voltage value. While the current is above the current limit value, the control
inhibits the one-shot start.
To properly set the current limit threshold, it should be noted that this is a valley current limit. Average current
depends on the inductor value, V
IN
V
OUT
and switching frequency.
The average output current in current limit is given by:
Eq 12
Thus, to set the current threshold, choose RILIM according to the following equation:
Eq 13
In current limit the system keeps the current constant until the output voltage meets the undervolatge threshold.
The negative valley current limit, for the sink mode, is set automatically at the same value of the positive valley
current limit. The average negative current limit differs from the positive average current limit by the ripple cur-
rent; this difference is due to the valley control technique.
The system accuracy is function of the exactness of the resistance connected to ILIM pin and the low side MOS-
FET RDS
ON
accuracy. Moreover the voltage on ILIM pin must range between 10mV and 1V to ensure the sys-
tem linearity.
Figure 6. Current limit schematic
I
L
t,C
SS
(
)
R
/R
K
I
t
V
SS
C
SS
-------------------------------------------------------------------
)
(
)
=
V
out
t,C
SS
(
)
Q t,C
C
out
)
------------------------
R
/R
K
I
t
2
C
out
V
SS
C
SS
2
----------------------------------------------------------------------
)
(
)
=
=
I
out
C
SS
(
)
V
C
R
ilim
/R
dson
K
C
I
SS
)
---------------------------------------------------------------------------
)
(
0.5
=
I
OUT
CL
I
max valley
I
2
----
+
=
max valley
R
Rds
on
-----------------
K
ILIM
=
Positive and negative current limit
R
ILIM
5μA
Current
Comparator
To
logic
PGN
D
PHASE
To inductor
LS
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| L6997D | STEP DOWN CONTROLLER FOR LOW VOLTAGE OPERATIONS |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| L6997-28 | 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT |
| L6997-5 | 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT; Accessory Type:Tuning Element; For Use With:High Quality Variable Reactance Tuning Microwave Cavities, Filters & other Resonant Structures |
| L6997-9 | 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT |
| L6997D | 功能描述:DC/DC 開關(guān)控制器 Adjustable Step-Down RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| L6997DTR | 功能描述:DC/DC 開關(guān)控制器 Adjustable Step-Down RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
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