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參數(shù)資料
| 型號： | LT1683EG |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Ultralow Noise Push-Pull DC/DC Controller |
| 中文描述： | SWITCHING CONTROLLER, 250 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | 5.30 MM, PLASTIC, SSOP-20 |
| 文件頁數(shù)： | 17/24頁 |
| 文件大?。?/td> | 237K |
| 代理商： | LT1683EG |
17
LT1683
1683f
APPLICATIU
The soft-start current will be initiated as soon as the part
turns on. Soft-start will be reinititated after a short-circuit
fault.
W
U
U
Thermal Considerations
Most of the IC power dissipation is derived from the V
IN
pin. The V
IN
current depends on a number of factors
including: oscillator frequency; loads on V5; slew settings;
gate charge current. Additional power is dissipated if V5
sinks current and during the MOSFET gate discharge.
The power dissipation in the IC will be the sum of:
1) The RMS V
IN
current times V
IN
2) V5 RMS sink current times 5V
3) The gate drive’s RMS discharge current times voltage
Because of the strong V
IN
component it is advantageous
to operate the LT1683 at as low a V
IN
as possible.
It is always recommended that package temperature be
measured in each application. The part has an internal
thermal shutdown to minimize the chance of IC destruc-
tion but this should not replace careful thermal design.
The thermal shutdown feature does not protect the exter-
nal MOSFETs. A separate analysis must be done for those
devices to insure that they are operating within safe limits.
Once IC power dissipation, P
DIS
, is determined die junc-
tion temperature is then computed as:
T
J
= T
AMB
+ P
DIS
θ
JA
where T
AMB
is ambient temperature and
θ
JA
is the package
thermal resistance. For the 20-pin SSOP,
θ
JA
is 100
°
C/W.
Magnetics
Design of magnetics is dependent on topology. The fol-
lowing details the design of the magnetics for a push-pull
converter. In this converter the transformer usually stores
little energy. The following equations should be consid-
ered as the starting point to building a prototype.
The following definitions will be used:
V
IN
= Input supply voltage
R
ON
= Switch-on resistance
I
SW
= Maximum switch current
V
OUT
= Desired output voltage
I
OUT
= Output current
f = Oscillator frequency
V
F
= Forward drop of the rectifier
Duty cycle is the major defining equation for this topology.
Note that the output L and C basically filter the chopped
voltage so duty cycle controls output voltage. N is the
turns ratio of the transformer. The turns ratio must be
large enough to ensure that the transformer can put out a
voltage equal to the output voltage plus the diode under
minimum input conditions. Note the transformer operates
at half the oscillator frequency (f).
N
V
V
DC
V
I
R
(
R
OUT
F
MAX
IN MIN
(
SW
ON
SENSE
=
+
(
)
+
)
[
]
2
)
DC
MAX
is the maximum duty cycle of each driver with
respect to the entire cycle, which consists of two periods
(A on and B on). So the effective duty cycle is 2 DC
MAX
.
The controller, in general, determines maximum duty
cycle. A 44% maximum duty cycle is a guaranteed value
for this part.
Remember to add sufficient margin in the turns ratio to
account for IR drops in the transformer windings, worst-
case diode forward drops and switch on voltage. Also at
very slow slew rates the effective DC may be reduced.
There are a number of ways to choose the inductance
value for L. We suggest as a starting point that L be
selected such that the converter is continuous at
I
OUT(MAX)
/4. If your minimum I
OUT
is higher than this or
your components can handle higher peak currents then
use a higher number.
D1
Figure 7. Push-Pull Topology
1:N
L
PRI
D2
L
C
R
OUT
R
SENSE
V
OUT
V
IN
1683 F07
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| LT1683EG#PBF | 功能描述:IC REG CTRLR PWM CM 20-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標準包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| LT1683EG#TR | 功能描述:IC REG CTRLR PWM CM 20-SSOP RoHS:否 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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 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:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LT1683EG#TRPBF | 功能描述:IC REG CTRLR PWM CM 20-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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 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:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LT1683IG | 功能描述:IC REG CTRLR PWM CM 20-SSOP RoHS:否 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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無 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:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
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