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參數(shù)資料
| 型號： | LTC1261 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | Switched Capacitor Regulated Voltage Inverter(開關(guān)電容穩(wěn)壓電壓反相器) |
| 中文描述： | 開關(guān)電容穩(wěn)壓逆變器（開關(guān)電容穩(wěn)壓電壓反相器） |
| 文件頁數(shù)： | 9/16頁 |
| 文件大?。?/td> | 265K |
| 代理商： | LTC1261 |
9
LTC1261
APPLICATIO
S I
FOR
ATIO
U
W
U
U
output with each clock cycle. The smaller capacitors
draw smaller pulses of current out of V
CC
as well, limiting
peak currents and reducing the demands on the input
supply. Table 1 shows recommended values of flying
capacitor vs maximum load capacity.
Table 1. Typical Max Load (mA) vs Flying Capacitor Value at
T
A
= 25
°
C, V
OUT
= –4V
FLYING
CAPACITOR
MAX LOAD (mA)
VALUE (
μ
F)
V
CC
= 5V DOUBLER MODE V
CC
= 3.3V TRIPLER MODE
0.1
22
0.047
16
0.033
8
0.022
4
0.01
1
MAX LOAD (mA)
20
15
11
5
3
The output capacitor performs two functions: it provides
output current to the load during half of the charge pump
cycle and its value helps to set the output ripple voltage.
For applications that are insensitive to output ripple, the
output bypass capacitor can be as small as 1
μ
F. To achieve
specified output ripple with 0.1
μ
F flying capacitors, the
output capacitor should be at least 3.3
μ
F. Larger output
capacitors will reduce output ripple further at the expense
of turn-on time.
Capacitor ESR
Output capacitor Equivalent Series Resistance (ESR) is
another factor to consider. Excessive ESR in the output
capacitor can fool the regulation loop into keeping the
output artificially low by prematurely terminating the charg-
ing cycle. As the charge pump switches to recharge the
output a brief surge of current flows from the flying
capacitors to the output capacitor. This current surge can
be as high as 100mA under full load conditions. A typical
3.3
μ
F tantalum capacitor has 1
or 2
of ESR; 100mA
×
2
= 200mV. If the output is within 200mV of the set point
this additional 200mV surge will trip the feedback com-
parator and terminate the charging cycle. The pulse dissi-
pates quickly and the comparator returns to the correct
state, but the RS latch will not allow the charge pump to
respond until the next clock edge. This prevents the charge
LTC1261CS8-4
V
CC
5V
C1
+
C1
–
4
6
5
2
3
OUT
0.1
μ
F
100pF
3.3
μ
F
10
COMP
LTC1261 F04
GND
V
OUT
= –4V
1
μ
F
+
3.3
μ
F
+
Figure 4. Output Filter Cuts Ripple Below 3mV
CAPACITOR SELECTION
Capacitor Sizing
The performance of the LTC1261 can be affected by the
capacitors it is connected to. The LTC1261 requires by-
pass capacitors to ground for both the V
CC
and OUT pins.
The input capacitor provides most of LTC1261’s supply
current while it is charging the flying capacitors. This
capacitor should be mounted as close to the package as
possible and its value should be at least five times larger
than the flying capacitor. Ceramic capacitors generally
provide adequate performance but avoid using a tantalum
capacitor as the input bypass unless there is at
least a
0.1
μ
F ceramic capacitor in parallel with it. The charge
pump capacitors are somewhat less critical since their
peak currents are limited by the switches inside the
LTC1261. Most applications should use 0.1
μ
F as the
flying capacitor value. Conveniently, ceramic capacitors
are the most common type of 0.1
μ
F capacitor and they
work well here. Usually the easiest solution is to use the
same capacitor type for both the input bypass and the
flying capacitors.
In applications where the maximum load current is well-
defined and output ripple is critical or input peak currents
need to be minimized, the flying capacitor values can be
tailored to the application. Reducing the value of the
flying capacitors reduces the amount of charge trans-
ferred with each clock cycle. This limits maximum output
current, but also cuts the size of the voltage step at the
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相關(guān)代理商/技術(shù)參數(shù) |
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| LTC1261CS | 功能描述:IC REG SWITCHED CAP INV 14SOIC 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:- 標準包裝:2,500 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，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 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:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤 |
| LTC1261CS#PBF | 功能描述:IC REG SWITCHED CAP INV 14SOIC 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:- 產(chǎn)品培訓(xùn)模塊:MIC23xxx HyperLight Load™ Regulators 標準包裝: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 |
| LTC1261CS#TR | 功能描述:IC REG SWITCHED CAP INV 14SOIC 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:- 標準包裝: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 |
| LTC1261CS#TRPBF | 功能描述:IC REG SWITCHED CAP INV 14SOIC 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:- 標準包裝: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 |
| LTC1261CS8 | 功能描述:IC REG SWITCHD CAP INV ADJ 8SOIC 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:- 標準包裝: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 |
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