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參數(shù)資料
| 型號： | LTC3780EG |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | DIODE SCHOTTKY SINGLE 25V 200mW 0.4V-vf 200mA-IFM 10mA-IF 0.5uA-IR SOD-123 3K/REEL |
| 中文描述： | 3 A SWITCHING CONTROLLER, 440 kHz SWITCHING FREQ-MAX, PDSO24 |
| 封裝： | 5.30 MM, PLASTIC, SSOP-24 |
| 文件頁數(shù)： | 22/28頁 |
| 文件大小： | 421K |
| 代理商： | LTC3780EG |
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LTC3780
3780f
In Buck mode, maximum sense voltage and the sense
resistance determines the maximum allowed inductor
valley current, which is:
I
mV
R
L MAXBUCK
(
SENSE
,
)
=
130
To further limit current in the event of a short circuit to
ground, the LTC3780 includes foldback current limiting. If
the output falls by more than 30%, then the maximum
sense voltage is progressively lowered to about one third
of its full value.
Fault Conditions: Overvoltage Protection
A comparator monitors the output for overvoltage condi-
tions. The comparator (OV) detects overvoltage faults
greater than 7.5% above the nominal output voltage.
When the condition is sensed, Switches A and C are turned
off, and Switches B and D are turned on until the overvolt-
age condition is cleared. During an overvoltage condition,
a negative current limit (V
SENSE
= –60mV) is set to limit
negative inductor current. When the sensed current in-
ductor current is lower than –60mV, Switch A and C are
turned on, and Switch B and D are turned off until the
sensed current is higher than –20mV. If the output is still
in overvoltage condition, Switch A and C are turned off,
and Switch B and D are turned on again.
Efficiency Considerations
The percent efficiency 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 efficiency and which change would
produce the most improvement. Although all dissipative
elements in circuit produce losses, four main sources
account for most of the losses in LTC3780 circuits:
1. DC I
2
R losses. These arise from the resistances of the
MOSFETs, sensing resistor, inductor and PC board
traces and cause the efficiency to drop at high output
currents.
2. Transition loss. This loss arises from the brief amount
of time Switch A or Switch C spends in the saturated
region during switch node transitions. It depends upon
the input voltage, load current, driver strength and
MOSFET capacitance, among other factors. The loss is
significant at input voltages above 20V and can be
estimated from:
Transition Loss
≈
1.7A
–1
V
IN2
I
OUT
C
RSS
f
where CR
SS
is the reverse transfer capacitance.
3. INTV
CC
current. This is the sum of the MOSFET driver
and control currents. This loss can be reduced by
supplying INTV
CC
current through the EXTV
CC
pin from
a high efficiency source, such as an output derived
boost network or alternate supply if available.
4. C
IN
and C
OUT
loss. The input capacitor has the difficult
job of filtering the large RMS input current to the regu-
lator in Buck mode. The output capacitor has the more
difficult job of filtering the large RMS output current in
Boost mode. Both C
IN
and C
OUT
are required to have low
ESR to minimize the AC I
2
R loss and sufficient capaci-
tance to prevent the RMS current from causing addi-
tional upstream losses in fuses or batteries.
5. Other losses. Schottky diode D1 and D2 are responsible
for conduction losses during dead time and light load
conduction periods. Inductor core loss occurs pre-
dominately at light loads. Switch C causes reverse
recovery current loss in Boost mode.
When making adjustments to improve efficiency, the input
current is the best indicator of changes in efficiency. If you
make a change and the input current decreases, then the
efficiency has increased. If there is no change in input
current, then there is no change in efficiency.
Design Example
As a design example, assume V
IN
= 5V to 18V (12V nomi-
nal), V
OUT
= 12V (5%), I
OUT(MAX)
= 5A and f = 400kHz.
APPLICATIU
W
U
U
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3780EG#PBF | 功能描述:IC REG CTRLR BST PWM CM 24-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標(biāo)準(zhǔn)包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 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:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| LTC3780EG#TR | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 24-Pin SSOP T/R |
| LTC3780EG#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 24-SSOP RoHS:是 類別: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 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 |
| LTC3780EGPBF | 制造商:Linear Technology 功能描述:4-Switch Buck-Boost Controller SSOP24 |
| LTC3780EUH | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 32-Pin QFN EP |
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