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參數(shù)資料
| 型號： | L5991 |
| 廠商： | 意法半導體 |
| 英文描述： | PRIMARY CONTROLLER WITH STANDBY |
| 中文描述： | 主控制器具有待機 |
| 文件頁數(shù)： | 12/19頁 |
| 文件大小： | 192K |
| 代理商： | L5991 |
in fig.27) holds the pin low in order to ensure that
the external MOS cannot be turned on acciden-
tally. The peculiarity of this circuit is its ability to
mantain the same sink capability (typically, 20mA
@ 1V)from V
CC
= 0V up to the start-upthreshold.
When the threshold is exceeded and the L5991
starts operating,V
REFOK
is pulled high (refer to fig.
27) and thecircuit is disabled.
It is then possible to omit the ”bleeder” resistor
(connected between the gate and the source of
the MOS) ordinarily used to prevent undesired
switching-on of the external MOS because of
some leakage current.
Pin 11.
PGND (Power Ground). The current loop
during the discharge of the gate of the external
MOS is closed through this pin. This loop should
be as short as possible to reduce EMI and run
separatelyfrom signal currents return.
Pin 12
. SGND(Signal Ground).This groundrefer-
ences the control circuitry of the IC, so all the
ground connections of the external parts related
to control functionsmust lead to this pin. In laying
out the PCB, care must be taken in preventing
switched high currents from flowing through the
SGND path.
Pin 13.
ISEN (Current Sense). This pin is to be
connected to the ”hot” lead of the current sense
resistor R
sense
(being the other one grounded),to
get a voltage ramp which is an image of the cur-
rent of the switch (I
Q
). When this voltage is equal
to:
V
13pk
=
I
Qpk
R
sense
=
V
COMP
1.4
3
(
9
)
the conductionof the switch is terminated.
To increase the noise immunity, a ”Leading Edge
Blanking” of about 100ns is internally realized as
shown in fig. 28. Because of that, the smoothing
RC filter between this pin and R
sense
could be re-
movedor, at least, considerablyreduced.
Pin 14.
DIS (Device Disable). When the voltage
on pin 14 rises above 2.5V the IC is shut down
and it is necessaryto pull VCC(IC supply voltage,
pin 8) below the UVLO threshold to allow the de-
vice to restart.
The pin can be driven by an external logic signal
in case of power management, as shown in fig.
29. It is also possible to realize an overvoltage
protection, as shown in the section ” Application
Ideas”.Ifused, bypass this pin to ground with a fil-
ter capacitor to avoid spurious activation due to
noise spikes. If not, it must be connected to
SGND.
Pin 15.
DC-LIM (Maximum Duty Cycle Limit). The
upper extreme, Dx, of the duty cycle range de-
pends on the voltage applied to this pin. Approxi-
mately,
D
x
R
T
R
T
+
230
(
10
)
if DC-LIM is grounded or left floating. Instead,
+
-
I
D97IN503
ISEN
0
3V
CLK
2V
+
-
+
-
1.2V
FROM E/A
OVERCURRENT
COMPARATOR
PWM
COMPARATOR
TO
PWM
LOGIC
TO FAULT
LOGIC
13
Figure 28. Internal LEB.
10
12
SGND
OUT
V
REFOK
D97IN538
Figure 27. Pull-Down of the output in UVLO.
L5991 - L5991A
12/23
相關PDF資料 |
PDF描述 |
|---|---|
| L5991A | PRIMARY CONTROLLER WITH STANDBY |
| L5991AD | PRIMARY CONTROLLER WITH STANDBY |
| L5991D | PRIMARY CONTROLLER WITH STANDBY |
| L5993 | CONSTANT POWER CONTROLLER |
| L5993D | CONSTANT POWER CONTROLLER |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| L5991_01 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:PRIMARY CONTROLLER WITH STANDBY |
| L5991A | 功能描述:電流型 PWM 控制器 Prog Current Mode RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| L5991AD | 功能描述:開關變換器、穩(wěn)壓器與控制器 Prog Current Mode RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| L5991AD13TR | 功能描述:電流型 PWM 控制器 Prog Current Mode RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| L5991D | 功能描述:電流型 PWM 控制器 Prog Current Mode RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
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