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參數(shù)資料
| 型號： | LTC1148HVCS-3.3#TR |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 250 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封裝： | 0.150 INCH, PLASTIC, SOP-14 |
| 文件頁數(shù)： | 5/20頁 |
| 文件大?。?/td> | 237K |
| 代理商： | LTC1148HVCS-3.3#TR |
13
LTC1148
LTC1148-3.3/LTC1148-5
114835fd
APPLICATIO S I FOR ATIO
W
UU
U
To prevent stray pickup a 100pF capacitor is suggested
across R1 located close to the LTC1148.
For Figure 1 applications with VOUT below 2V, or when
RSENSE is moved to ground, the current sense comparator
inputs operate near ground. When the current comparator
is operated at less than 2V common mode, the off time
increases approximately 40%, requiring the use of a
smaller timing capacitor CT.
Auxiliary Windings – Suppressing Burst Mode
Operation
The LTC1148 synchronous switch removes the normal
limitation that power must be drawn from the inductor
primary winding in order to extract power from auxil-
iary windings. With synchronous switching, auxiliary
outputs may be loaded without regard to the primary
output load, providing that the loop remains in continu-
ous mode operation.
Burst Mode operation can be suppressed at low output
currents with a simple external network which cancels the
25mV minimum current comparator threshold. This tech-
nique is also useful for eliminating audible noise from
certain types of inductors in high current (IOUT > 5A)
applications when they are lightly loaded.
An external offset is put in series with the SENSE – pin to
subtract from the built-in 25mV offset. An example of this
technique is shown in Figure 6. Two 100 resistors are
inserted in series with the leads from the sense resistor.
and δP = δN = 0.007(63 – 25) = 0.27. The required RDS(ON)
for each MOSFET can now be calculated:
P-Ch RDS(ON) =
12(0.25)
5(2)2 (1.27)
= 0.12
N-Ch RDS(ON) =
12(0.25)
7(2)2 (1.27)
= 0.085
The P-channel requirement can be met by a Si9430DY,
while the N-channel requirement is exceeded by a
Si9410DY. Note that the most stringent requirement for
the N-channel MOSFET is with VOUT = 0 (i.e., short circuit).
During a continuous short circuit, the worst-case
N-channel dissipation rises to:
PN = ISC(AVG)2(RDS(ON))(1 + δN)
With the 0.05 sense resistor ISC(AVG) = 2A will result,
increasing the 0.085 N-channel dissipation to 450mW at
a die temperature of 73°C.
CIN will require an RMS current rating of at least 1A at
temperature, and COUT will require an ESR of 0.05 for
optimum efficiency.
Now allow VIN to drop to its minimum value. At lower input
voltages the operating frequency will decrease and the
P-channel will be conducting most of the time, causing its
power dissipation to increase. At VIN(MIN) = 7V:
fMIN = (1/2.92s)[1 – (5V/7V)] = 98kHz
PP =
5V(0.12)(2A)2(1.27)
7V
= 435mW
This last step is necessary to assure that the power
dissipation and junction temperature of the P-channel are
not exceeded.
LTC1148 Adjustable Applications
When an output voltage other than 3.3V or 5V is required,
the LTC1148 adjustable version is used with an external
resistive divider from VOUT to VFB Pin 9 (see Figure 9). The
regulated voltage is determined by:
VOUT = 1.25
)
)1 + R2
R1
Figure 6. Suppression of Burst Mode Operation
RSENSE
1000pF
R2
100
R1
100
R3
+
COUT
VOUT
SENSE+ (PIN 8)
SENSE – (PIN 7)
LTC1148 F06
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
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| LTC1148HVCS5 | 制造商:LT 功能描述:REREALED |
| LTC1148HVCS-5 | 功能描述:IC REG CTRLR BUCK PWM CM 14-SOIC 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 |
| LTC1148HVCS-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 14-SOIC 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:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 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 ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC1148HVCS-5#TR | 功能描述:IC REG CTRLR BUCK PWM CM 14-SOIC 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 |
| LTC1148HVCS-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 14-SOIC 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:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 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 ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
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