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參數(shù)資料
| 型號： | LTC3728LIUH-1#TR |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3 A DUAL SWITCHING CONTROLLER, 590 kHz SWITCHING FREQ-MAX, PQCC32 |
| 封裝： | 5 X 5 MM, PLASTIC, MO-220WHHD, QFN-32 |
| 文件頁數(shù)： | 15/32頁 |
| 文件大?。?/td> | 475K |
| 代理商： | LTC3728LIUH-1#TR |
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LTC3728L-1
22
3728l1fc
APPLICATIONS INFORMATION
If VSEC drops below this level, the FCB voltage forces
temporary continuous switching operation until VSEC is
again above its minimum.
In order to prevent erratic operation if no external connec-
tions are made to the FCB pin, the FCB pin has a 0.18μA
internal current source pulling the pin high. Include this
current when choosing resistor values R5 and R6.
The following table summarizes the possible states avail-
able on the FCB pin:
Table 1
FCB PIN
CONDITION
0V to 0.75V
Forced Continuous Both Controllers
(Current Reversal Allowed—
Burst Inhibited)
0.85V < VFCB < 4.3V
Minimum Peak Current Induces
Burst Mode Operation
No Current Reversal Allowed
Feedback Resistors
Regulating a Secondary Winding
>4.8V
Burst Mode Operation Disabled
Constant Frequency Mode Enabled
No Current Reversal Allowed
No Minimum Peak Current
Voltage Positioning
Voltage positioning can be used to minimize peak-to-peak
output voltage excursions under worst-case transient
loading conditions. The open-loop DC gain of the control
loop is reduced depending upon the maximum load step
specications. Voltage positioning can easily be added
to either or both controllers by loading the ITH pin with
a resistive divider having a Thevenin equivalent voltage
source equal to the midpoint operating voltage range of
the error amplier, or 1.2V (see Figure 8).
The resistive load reduces the DC loop gain while main-
taining the linear control range of the error amplier.
The maximum output voltage deviation can theoretically
be reduced to half or alternatively the amount of output
capacitance can be reduced for a particular application. A
complete explanation is included in Design Solutions 10.
(See www.linear.com)
Efciency Considerations
The percent efciency of a switching regulator is equal to
the output power divided by the input power times 100%.
It is often useful to analyze individual losses to determine
what is limiting the efciency and which change would
produce the most improvement. Percent efciency can
be expressed as:
%Efciency = 100% – (L1 + L2 + L3 + ...)
where L1, L2, etc. are the individual losses as a percent-
age of input power.
Although all dissipative elements in the circuit produce
losses, four main sources usually account for most of the
losses in LTC3728L-1 circuits: 1) IC VIN current (including
loading on the 3.3V internal regulator), 2) INTVCC regula-
tor current, 3) I2R losses, 4) Topside MOSFET transition
losses.
1. The VIN current has two components: the rst is the DC
supply current given in the Electrical Characteristics table,
which excludes MOSFET driver and control currents; the
second is the current drawn from the 3.3V linear regulator
output. VIN current typically results in a small (<0.1%)
loss.
Figure 8. Active Voltage Positioning
Applied to the LTC3728L-1
ITH
RC
RT1
INTVCC
CC
3728L1 F08
LTC3728L-1
RT2
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| LTC3728LXCUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:2,000 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:50% 電源電壓:9 V ~ 10 V 降壓:無 升壓:是 回掃:是 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:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR) |
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