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參數(shù)資料
| 型號： | LT3512MPMS#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.8 A SWITCHING REGULATOR, 650 kHz SWITCHING FREQ-MAX, PDSO12 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-16/12 |
| 文件頁數(shù)： | 6/26頁 |
| 文件大?。?/td> | 244K |
| 代理商： | LT3512MPMS#PBF |
LT3512
14
3512fa
APPLICATIONS INFORMATION
Figure 7. Undervoltage Lockout (UVLO)
APPLICATION DESIGN CONSIDERATIONS
Iterative Design Process
The LT3512 uses a unique sampling scheme to regulate
the isolated output voltage. The use of this isolated scheme
requires a simple iterative process to choose feedback
resistors and temperature compensation. Feedback re-
sistor values and temperature compensation resistance
is heavily dependent on the application, transformer and
output diode chosen.
Once resistor values are fixed after iteration, the values
will produce consistent output voltages with the chosen
transformer and output diode. Remember, the turns ratio
of the transformer must be guaranteed within ±1%. The
transformer vendors mentioned in this data sheet can
build transformers to this specification.
Selecting RFB and RREF Resistor Values
The following section provides an equation for setting
RFB and RREF values. The equation should only serve
as a guide. Follow the procedure outlined in the Design
Procedure to set accurate values for RFB, RREF and RTC
using the iterative design procedure.
Rearrangement of the expression for VOUT in the Tempera-
ture Compensation section, developed in the Operations
section, yields the following expression for RFB:
RFB =
RREF NPS VOUT + VF
()+ V
TC
VBG
where:
VOUT = Output voltage
VF = Switching diode forward voltage
NPS = Effective primary-to-secondary turns ratio
VTC = 0.55V
This equation assumes:
R
TC =
R
FB
N
PS
The equation assumes the temperature coefficients of
the diode and VTC are equal, which is a good first order
approximation.
LT3512
EN/UVLO
GND
R2
R1
VIN
3512 F07
RUN/STOP
CONTROL
(OPTIONAL)
Strictly speaking, the above equation defines RFB not as an
absolute value, but as a ratio of RREF. So the next question
is, what is the proper value for RREF? The answer is that
RREF should be approximately 10k. The LT3512 is trimmed
and specified using this value of RREF. If the impedance of
RREF varies considerably from 10k, additional errors will
result. However, a variation in RREF of several percent is
acceptable. This yields a bit of freedom in selecting stan-
dard 1% resistor values to yield nominal RFB/RREF ratios.
Undervoltage Lockout (UVLO)
A resistive divider from VIN to the EN/UVLO pin imple-
ments undervoltage lockout (UVLO). Figure 7 shows this
configuration. The EN/UVLO pin threshold is set at 1.21V.
In addition, the EN/UVLO pin draws 2.6μA when the volt-
age at the pin is below 1.21V. This current provides user
programmable hysteresis based on the value of R1. The
effective UVLO thresholds are:
VIN(UVLO,RISING) =
1.2V (R1
+ R2)
R2
+ 2.6A R1
VIN(UVLO,FALLING) =
1.2V (R1
+ R2)
R2
Figure 7 also shows the implementation of external shut-
down control while still using the UVLO function. The
NMOS grounds the EN/UVLO pin when turned on, and
puts the LT3512 in shutdown with quiescent current draw
of less than 1μA.
Minimum Load Requirement
The LT3512 recovers output voltage information using the
flyback pulse. The flyback pulse occurs once the switch
turns off and the secondary winding conducts current. In
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| LT3513EUHF#PBF | 功能描述:IC REG 5-OUT FOR TFT-LCD 38QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標準包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件 |
| LT3513EUHF#TRPBF | 功能描述:IC REG 5-OUT FOR TFT-LCD 38QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標準包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件 |
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| LT3513EUHF-TRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:2MHz High Current 5-Output Regulator for TFT-LCD Panels |
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