參數(shù)資料
型號(hào)： LTC1709EG-7
廠商： LINEAR TECHNOLOGY CORP
元件分類(lèi)： 穩(wěn)壓器
英文描述： RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
中文描述： 3 A SWITCHING CONTROLLER, 360 kHz SWITCHING FREQ-MAX, PDSO36
封裝： 0.209 INCH, PLASTIC, SSOP-36
文件頁(yè)數(shù)： 12/28頁(yè)
文件大小： 319K
代理商： LTC1709EG-7
12
LTC1709-7
APPLICATIU
The basic LTC1709-7 application circuit is shown in
Figure1 on the first page. External component selection
begins with the selection of the inductor(s) based on
ripple current requirements and continues with the
R
SENSE1, 2
resistor selection using the calculated peak
inductor current and/or maximum current limit. Next, the
power MOSFETs and D1 and D2 are selected. The oper-
ating frequency and the inductor are chosen based mainly
on the amount of ripple current. Finally, C
IN
is selected for
its ability to handle the input ripple current (that
PolyPhase
TM
operation minimizes) and C
OUT
is chosen
with low enough ESR to meet the output ripple voltage
and load step specifications (also minimized with
PolyPhase). Current mode architecture provides inherent
current sharing between output stages. The circuit shown
in Figure1 can be configured for operation up to an input
voltage of 28V (limited by the external MOSFETs). Current
mode control allows the ability to connect the two output
stages to two different input power supply rails. A heavy
output load can take some power from each input supply
according to the selection of the R
SENSE
resistors.
W
U
U
R
SENSE
Selection For Output Current
R
SENSE1, 2
are chosen based on the required peak output
current. The LTC1709-7 current comparator has a maxi-
mum threshold of 75mV/R
SENSE
and an input common
mode range of SGND to 1.1(INTV
CC
). The current com-
parator threshold sets the peak inductor current, yielding
a maximum average output current I
MAX
equal to the peak
value less half the peak-to-peak ripple current,
I
L
.
Assuming a common input power source for each output
stage and allowing a margin for variations in the
LTC1709-7 and external component values yields:
R
SENSE
= 2(50mV/I
MAX
)
Operating Frequency
The LTC1709-7 uses a constant frequency, phase-lock-
able architecture with the frequency determined by an
internal capacitor. This capacitor is charged by a fixed
current plus an additional current which is proportional
to the voltage applied to the PLLFLTR pin. Refer to Phase-
Locked Loop and Frequency Synchronization for addi-
tional information.
A graph for the voltage applied to the PLLFLTR pin vs
frequency is given in Figure2. As the operating frequency
is increased the gate charge losses will be higher, reducing
efficiency (see Efficiency Considerations). The maximum
switching frequency is approximately 310kHz.
Figure 2. Operating Frequency vs V
PLLFLTR
PolyPhase is a registered trademark of Linear Technology Corporation.
OPERATING FREQUENCY (kHz)
120
170
220
270
320
P
17097 F02
2.5
2.0
1.5
1.0
0.5
0
Inductor Value Calculation and Output Ripple Current
The operating frequency and inductor selection are inter-
related in that higher operating frequencies allow the use
of smaller inductor and capacitor values. So why would
anyone ever choose to operate at lower frequencies with
larger components The answer is efficiency. A higher
frequency generally results in lower efficiency because
MOSFET gate charge and transition losses increase di-
rectly with frequency. In addition to this basic tradeoff, the
effect of inductor value on ripple current and low current
operation must also be considered. The PolyPhase ap-
proach reduces both input and output ripple currents
while optimizing individual output stages to run at a lower
fundamental frequency, enhancing efficiency.
The inductor value has a direct effect on ripple current.
The inductor ripple current
I
L
per individual section, N,
decreases with higher inductance or frequency and
increases with higher V
IN
or V
OUT
:
I
V
fL
V
V
L
OUT
OUT
IN
=
1
where f is the individual output stage operating frequency.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC1709EG-7#PBF 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 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(wú) 升壓:是 回掃:是 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR)
LTC1709EG-7#TR 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)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(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC1709EG-7#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)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(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC1709EG-8 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)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(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
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