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參數(shù)資料
| 型號： | LTC1261CS8 |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Switched Capacitor Regulated Voltage Inverter |
| 中文描述： | SWITCHED CAPACITOR REGULATOR, 550 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | PLASTIC, SO-8 |
| 文件頁數(shù)： | 10/16頁 |
| 文件大?。?/td> | 310K |
| 代理商： | LTC1261CS8 |
10
LTC1261
Most of this resistance is already provided by the internal
switches in the LTC1261 (especially in tripler mode). More
than 1
or 2
of ESR on the flying capacitors will start to
affect the regulation at maximum load.
RESISTOR SELECTION
Resistor selection is easy with the fixed output versions of
the LTC1261—no resistors are needed! Selecting the
right resistors for the adjustable parts is only a little more
difficult. A resistor divider should be used to divide the
signal at the output to give 1.24V at the ADJ pin with
respect to V
OUT
(Figure 6). The LTC1261 uses a positive
reference with respect to V
OUT
, not a negative reference
with respect to ground (Figure 2 shows the reference
connection). Be sure to keep this in mind when connecting
the resistors! If the initial output is not what you expected,
try swapping the two resistors.
APPLICATIO
S I
N
FOR
ATIO
U
pump from going into very high frequency oscillation
under such conditions but it also creates an output error
as the feedback loop regulates based on the top of the
spike, not the average value of the output (Figure 5). The
resulting output voltage behaves as if a resistor of value
C
ESR
×
(I
PK
/I
AVE
)
was placed in series with the output. To
avoid this nasty sequence of events connect a 0.1
μ
F
ceramic capacitor in parallel with the larger output capaci-
tor. The ceramic capacitor will “eat” the high frequency
spike, preventing it from fooling the feedback loop, while
the larger but slower tantalum or aluminum output capaci-
tor supplies output current to the load between charge
cycles.
W
U
LOW ESR
OUTPUT CAP
CLOCK
V
AVERAGE
V
SET
COMP1
OUTPUT
V
OUT
HIGH ESR
OUTPUT CAP
V
AVERAGE
V
SET
COMP1
OUTPUT
LTC1261 F05
V
OUT
Note that ESR in the flying capacitors will not cause the
same condition; in fact, it may actually improve the situa-
tion by cutting the peak current and lowering the ampli-
tude of the spike. However, more flying capacitor ESR is
not necessarily better. As soon as the RC time constant
approaches half of a clock period (the time the capacitors
have to share charge at full duty cycle) the output current
capability of the LTC1261 will begin to diminish. For 0.1
μ
F
flying capacitors, this gives a maximum total series resis-
tance of:
)
550kHz
=
/ 0.1
μ
F = 9.1
1
2
)
t
CLK
C
FLY
1
2
)
)
1
Figure 5. Output Ripple with Low and High ESR Capacitors
Figure 6. External Resistor Connections
LTC1261
GND
R1
6 (4*)
10 (5*)
11 (6*)
*LTC1261CS8
LTC1261 F06
V
OUT
= –1.24V
R2
R1 + R2
R2
ADJ
OUT
(
)
The 14-pin adjustable parts include a built-in resistor
string which can provide an assortment of output voltages
by using different pin-strapping options at the R0, R1, and
R
ADJ
pins (Table 2). The internal resistors are roughly
124k, 226k, 100k, and 50k (see Figure 2) giving output
options of –3.5V, –4V, –4.5V, and –5V. The resistors are
carefully matched to provide accurate divider ratios, but
the absolute values can vary substantially from part to
part. It is not a good idea to create a divider using an
external resistor and one of the internal resistors unless
the output voltage accuracy is not critical.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1261CS8#PBF | 功能描述:IC REG SWITCHD CAP INV ADJ 8SOIC 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 |
| LTC1261CS8#TR | 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(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 |
| LTC1261CS8#TRPBF | 功能描述:IC REG SWITCHD CAP INV ADJ 8SOIC 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 |
| LTC1261CS8-4 | 功能描述:IC REG SWITCHD CAP INV -4V 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(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 |
| LTC1261CS8-4#PBF | 功能描述:IC REG SWITCHD CAP INV -4V 8SOIC 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 |
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