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參數(shù)資料
| 型號： | LTC3617EUDD#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 14 A SWITCHING REGULATOR, 2700 kHz SWITCHING FREQ-MAX, PQCC24 |
| 封裝： | 3 X 5 MM, LEAD FREE, PLASTIC, QFN-24 |
| 文件頁數(shù)： | 5/20頁 |
| 文件大?。?/td> | 471K |
| 代理商： | LTC3617EUDD#PBF |
LTC3617
13
3617fa
applications inForMation
Since the ESR of a ceramic capacitor is so low, the input
and output capacitor must instead fulfill a charge storage
requirement.Duringaloadstep,theoutputcapacitormust
instantaneously supply the current until the feedback loop
raises the switch current enough to support the load. The
timerequiredforthefeedbacklooptorespondisdependent
on the compensation components and the output capaci-
tor size. Typically, 3 to 4 switching cycles are required to
respond to a load step, but only in the first cycle does the
output drop linearly. The output droop, VDROOP, is usually
about2to4timesthelineardropofthefirstcycle;however,
this behavior can vary depending on the compensation
component values. Thus, a good place to start is with the
output capacitor size of approximately:
COUT ≈
3.5
IOUT
fSW VDROOP
This is only an approximation; more capacitance may
be needed depending on the duty cycle and load step
requirements.
Inmostapplications,theinputcapacitorismerelyrequired
to supply high frequency bypassing, since the impedance
to the supply is very low.
Output Voltage Programming
In most applications, VOUT is connected directly to VFB.
The output voltage will be equal to one-half of the voltage
on the VDDQIN pin for this case.
VOUT =
VDDQIN
2
If a different output relationship is desired, an external
resistor divider from VOUT to VFB can be used. The output
voltagewillthenbesetaccordingtothefollowingequation:
VOUT =
VDDQIN
2
1
+
R2
R1
Internal and External Compensation
The regulator loop response can be checked by looking at
the load current transient response. Switching regulators
take several cycles to respond to a step in DC load current.
When a load step occurs, VOUT shifts by an amount equal
to
ILOAD ESR, where ESR is the effective series resis-
tance of COUT. ILOAD also begins to charge or discharge
COUT, generating the feedback error signal that forces the
regulator to adapt to the current change and return VOUTto
its steady-state value. During this recovery time VOUT can
be monitored for excessive overshoot or ringing, which
would indicate a stability problem. The availability of the
ITH pin allows the transient response to be optimized over
a wide range of output capacitance.
The ITH external components (RC and CC) shown in Fig-
ure 1 provide adequate compensation as a starting point
for most applications. The values can be modified slightly
to optimize transient response once the final PCB layout
is done and the particular output capacitor type and value
have been determined. The output capacitors need to be
selected because the various types and values determine
the loop gain and phase. The gain of the loop will be in-
creased by increasing RC and the bandwidth of the loop
will be increased by decreasing CC. If RC is increased by
the same factor that CC is decreased, the zero frequency
will be kept the same, thereby keeping the phase shift the
same in the most critical frequency range of the feedback
loop. The output voltage settling behavior is related to the
stability of the closed-loop system. The external capaci-
tor, CC1, (Figure 1) is not needed for loop stability, but it
helps filter out any high frequency noise that may couple
onto that node.
LTC3617
VFB
VOUT
SGND
R1
3617 F03
R2
Figure 3. Setting the Output Voltage
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| LTC3617IUDD#PBF | 功能描述:IC REG SYNC 6A BUCK 24QFN 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 供應商設備封裝:48-QFN（7x7） 包裝:管件 |
| LTC3617IUDD#TRPBF | 功能描述:IC REG SYNC 6A BUCK 24QFN 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 供應商設備封裝:48-QFN（7x7） 包裝:管件 |
| LTC3618EFE#PBF | 功能描述:IC REG DUAL SYNC 3A BUCK 24TSSOP 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 供應商設備封裝:48-QFN（7x7） 包裝:管件 |
| LTC3618EFE#TRPBF | 功能描述:IC REG DUAL SYNC 3A BUCK 24TSSOP 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 供應商設備封裝:48-QFN（7x7） 包裝:管件 |
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