- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄385505 > LTC1751-5 (Linear Technology Corporation) Micropower, Regulated Charge Pump DC/DC Converters PDF資料下載
參數(shù)資料
| 型號： | LTC1751-5 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | Micropower, Regulated Charge Pump DC/DC Converters |
| 中文描述： | 微功耗，穩(wěn)壓電荷泵DC / DC轉(zhuǎn)換器 |
| 文件頁數(shù)： | 8/12頁 |
| 文件大?。?/td> | 211K |
| 代理商： | LTC1751-5 |
8
LTC1751/LTC1751-3.3/LTC1751-5
APPLICATIOU
Flying Capacitor Selection
Warning: A polarized capacitor such as tantalum or
aluminum should never be used for the flying capacitor
since ts voltage can reverse upon start-up of he LTC1751.
Low ESR ceramic capacitors should always be used for
the flying capacitor.
The flying capacitor controls the strength of the charge
pump. In order to achieve the rated output current, it is
necessary to have at least 0.6
μ
F of capacitance for the
flying capacitor. Capacitors of different materials lose their
capacitance with higher temperature and voltage at differ-
ent rates. For example, a ceramic capacitor made of X7R
material will retain most of its capacitance from –40
°
C to
85
°
C, whereas, a Z5U or Y5V style capacitor will lose
considerable capacitance over that range. Z5U and Y5V
capacitors may also have a very strong voltage coefficient
causing them to lose 50% or more of their capacitance
when the rated voltage is applied. The capacitor
manufacturer’s data sheet should be consulted to deter-
mine what value of capacitor is needed to ensure 0.6
μ
F at
all temperatures and voltages.
Generally an X7R ceramic capacitor is recommended for
the flying capacitor with a minimum value of 1
μ
F. For very
low load applications, it may be reduced to 0.01
μ
F-0.68
μ
F.
A smaller flying capacitor delivers less charge per clock
cycle to the output capacitor resulting in lower output
ripple. The output ripple is reduced at the expense of
maximum output current and efficiency.
The theoretical minimum output resistance of a voltage
doubling charge pump is given by:
W
U
U
R
V
V
I
fC
OUT MIN
(
IN
OUT
OUT
)
–
≡
=
2
1
Where f if the switching frequency and C is the value of the
flying capacitor. (Using units of MHz and
μ
F is convenient
since they cancel each other.) Note that the charge pump
will typically be weaker than the theoretical limit due to
additional switch resistance. However, for light load appli-
cations, the above expression can be used as a guideline
in determining a starting capacitor value.
Below is a list of ceramic capacitor manufacturers and
how to contact them:
AVX
Kemet
Murata
Taiyo Yuden
Vishay
www.avxcorp.com
www.kemet.com
www.murata.com
www.t-yuden.com
www.vishay.com
Output Ripple
Low frequency regulation moderipple exists due to the
hysteresis in the sense comparator and propagation
delays in the charge pump control circuits. The amplitude
and frequency of this ripple are heavily dependent on the
load current, the input voltage and the output capacitor
size. For large V
IN
the ripple voltage can become substan-
tial because the increased strength of the charge pump
causes fast edges that may outpace the regulation cir-
cuitry. In some cases, rather than bursting, a single
output cycle may be enough to boost the output voltage
into or possibly beyond regulation. In these cases the
average output voltage will climb slightly. For large input
voltages a larger output capacitor will ensure that burst-
ing always occurs, thus mitigating possible DC problems.
Generally the regulation ripple has a sawtooth shape
associated with it.
A high frequency ripple component may also be present
on the output capacitor due to the charge transfer action
of the charge pump. In this case, the output can display a
voltage pulse during the output-charging phase. This
pulse results from the product of the charging current and
the ESR of the output capacitor. It is proportional to the
input voltage, the value of the flying capacitor and the ESR
of the output capacitor.
For example, typical combined output ripple for an
LTC1751-5 with V
IN
= 3V under maximum load is
75mV
P-P
with a low ESR 10
μ
F output capacitor. A smaller
output capacitor and/or larger output current load will
result in higher ripple due to higher output voltage slew
rates.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LTC1751 | Micropower, Regulated Charge Pump DC/DC Converters |
| LTC1751-3.3 | Micropower, Regulated Charge Pump DC/DC Converters |
| LTC1753 | 9-Bit D-Type Transparent Read-Back Latches With 3-State Outputs 24-PDIP 0 to 70 |
| LTC1753CG | Isolated Flyback Switching Regulator with 9V Output |
| LTC1753CSW | 10-Bit D-Type Transparent Read-Back Latches 24-SOIC 0 to 70 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1751EMS8 | 功能描述:IC REG SWITCHD CAP DBL ADJ 8MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
| LTC1751EMS8#PBF | 功能描述:IC REG SWITCHD CAP DBL ADJ 8MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:250 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V 輸入電壓:2.05 V ~ 6 V PWM 型:電壓模式 頻率 - 開關(guān):2MHz 電流 - 輸出:500mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:6-UFDFN 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:6-SON（1.45x1） 產(chǎn)品目錄頁面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2 |
| LTC1751EMS8#TR | 功能描述:IC REG SWITCHD CAP DBL ADJ 8MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
| LTC1751EMS8#TRPBF | 功能描述:IC REG SWITCHD CAP DBL ADJ 8MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
| LTC1751EMS8-3.3 | 功能描述:IC REG SWITCHED CAP DBL 8MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 產(chǎn)品培訓(xùn)模塊:MIC23xxx HyperLight Load™ Regulators 標(biāo)準(zhǔn)包裝:5,000 系列:HyperLight Load® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.8V 輸入電壓:2.7 V ~ 5.5 V PWM 型:混合物 頻率 - 開關(guān):4MHz 電流 - 輸出:2A 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤，8-MLF? 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-MLF?（2x2） 產(chǎn)品目錄頁面:1094 (CN2011-ZH PDF) 其它名稱:576-3303-2 |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。