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參數(shù)資料
| 型號： | LT1952IGN |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Single Switch Synchronous Forward Controller |
| 中文描述： | 1 A SWITCHING CONTROLLER, 560 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 0.150 INCH, PLASTIC, SSOP-16 |
| 文件頁數(shù)： | 13/24頁 |
| 文件大小： | 252K |
| 代理商： | LT1952IGN |
LT1952
13
1952f
APPLICATIU
between system input supply and V
IN
. Once the part is
turned on, input current increases to drive the IC (4.5mA)
and the output drivers (I
DRIVE
). A large enough capacitor
is chosen at the V
IN
pin to prevent V
IN
falling below 8.5V
before an auxiliary winding in the converter takes over
supply to V
IN
. This technique allows a simple resistor/
capacitor for start-up which draws low power from the
system supply to the converter. The values for R
START
and
C
START
are given by:
R
START(MAX)
= (V
S(MIN)
– V
IN ON(max)
)/I
START(MAX)
C
START(MIN)
= (I
Q(MAX)
+ I
DRIVE(MAX)
) t
START
/
V
IN HYST(MIN)
Example:
For V
S(MIN)
= 36V, V
IN ON(MAX)
= 15.75V,
I
START(MAX)
= 700
μ
A, I
Q(MAX)
= 5.5mA,
I
DRIVE(MAX)
= 5mA, V
IN HYST(MIN)
= 3.75V
and t
START
= 100
μ
s,
R
START
= (36 – 15.75)/700
μ
A = 28.9k (choose 28.7k)
C
START
= (5.5mA + 5mA) 100
μ
s/3.75V = 0.28
μ
F
(typically choose
≥
1
μ
F)
For system input voltages exceeding the absolute maxi-
mum rating of the LT1952 V
IN
pin, an external zener should
be connected from the V
IN
pin to ground. This covers the
condition where V
IN
charges past V
IN ON
(typically 14.25V)
but the part does not turn on because SD_V
SEC
< 1.32V. In
this condition V
IN
will continue to charge towards system
W
U
U
Figure 4. Low Power Start-Up
V
IN
, possibly exceeding the rating for the V
IN
pin. The zener
voltage should obey V
IN ON(MAX)
< V
Z
< 25V.
Programming Oscillator Frequency
The oscillator frequency (f
OSC
) of the LT1952 is pro-
grammed using an external resistor (R
OSC
) connected
between the R
OSC
pin and ground. Figure 5 shows typical
f
OSC
vs. R
OSC
resistor values. The LT1952 free-running
oscillator frequency is programmable in the range of
100kHz to 500kHz.
Stray capacitance and potential noise pickup on the R
OSC
pin should be minimized by placing the R
OSC
resistor as
close as possible to the R
OSC
pin and keeping the area of
the R
OSC
node as small as possible. The ground side of the
R
OSC
resistor should be returned directly to the (analog
ground) GND pin. R
OSC
can be calculated by,
R
OSC
= 9.125k [(4100k/f
OSC
) – 1]
Figure 5. Oscillator Frequency (f
OSC
) vs R
OSC
R
OSC
(k
)
50
F
400
1952 F05
100
150
250
200
300
350
500
450
400
350
300
250
200
150
100
1.32V
SYSTEM
INPUT (V
S
)
FROM AUXILIARY WINDING
*FOR V
S
> 25V, ZENER D1 RECOMMENDED
(V
IN ON(MAX)
< V
Z
< 25V)
1952 F04
V
IN
LT1952
(14.25V ON, 8.75V OFF)
C
START
D1*
R
START
+
–
Programming Leading Edge Blank Time
For PWM controllers driving external MOSFETs, noise can
be generated at the source of the MOSFET during gate rise
time and some time thereafter. This noise can potentially
exceed the OC and I
SENSE
pin thresholds of the LT1952 to
cause premature turn off of SOUT and OUT in addition to
false trigger of soft-start. The LT1952 provides program-
mable leading edge blanking of the OC and I
SENSE
com-
parator outputs to avoid false current sensing during
MOSFET switching.
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| LT1952IGN#PBF | 功能描述:IC REG CTRLR ISO PWM CM 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LT1952IGN#TR | 制造商:Linear Technology 功能描述:Current Mode PWM Controller 16-Pin SSOP N T/R |
| LT1952IGN#TRPBF | 功能描述:IC REG CTRLR ISO PWM CM 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LT1952IGN-1 | 制造商:Linear Technology 功能描述:Current Mode PWM Controller 16-Pin SSOP N |
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