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參數(shù)資料
| 型號： | LTC1695 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | SMBus/I 2 C Fan Speed Controller in SOT-23(SMBus/I 2 C 風扇速度控制器（SOT-23封裝）) |
| 中文描述： | 的SMBus /的I 2 C風扇調(diào)速器采用SOT - 23（的SMBus /的I 2 C風扇速度控制器（采用SOT - 23封裝）） |
| 文件頁數(shù)： | 13/20頁 |
| 文件大?。?/td> | 204K |
| 代理商： | LTC1695 |
LTC1695
13
Linear Regulator Loop Compensation
The LTC1695’s linear regulator approach is a simple and
practical scheme for fan speed control featuring a wide and
linear dynamic range. It also introduces less noise into the
system supply rail, compared with a PWM scheme (fixed
frequency, variable duty cycle), switching regulator topol-
ogy or simple ON-OFF control.
The LTC1695 linear regulator feedback loop requires a
capacitor at its output to stabilize the loop over the output
voltage and load current range. The output capacitor value
and the capacitor’s ESR value are critical in stabilizing the
LTC1695 feedback loop.
A
≥
1
μ
F general purpose, low to medium ESR (0.1
to 5
)
tantalum or aluminium electrolytic capacitor is sufficient
for most applications. These capacitor types offer a low-
cost advantage, particularly for fan speed control applica-
tions. As the output capacitance value increases, stability
improves. A typical 4.7
μ
F, 1
ESR surface mount tanta-
lum capacitor is recommended for the optimum transient
response and frequency stability across temperature, V
OUT
and I
LOAD
. Refer to the load transient response waveforms
in the Typical Performance Characteristics section.
The selection of the capacitor for C
OUT
must be evaluated
by the user for temperature variation of the capacitance
and ESR value and the voltage coefficient of the capacitor
value. For example, the ESR of aluminium electrolytic
capacitors can increase dramatically at cold temperature.
Therefore, the regulator may be stable at room tempera-
ture but oscillate at cold temperature. Ceramic capacitors
with Z5U and Y5 dielectrics provide high capacitance
values in a small package, but exhibit strong voltage and
temperature coefficients (–80% in some cases). In addi-
tion, the ESR of surface mount ceramic capacitors is too
low (<0.1
) to provide adequate phase-lead in the feed-
back loop for stability.
Fan Load and C
LOAD
Referring to Figure 4, C
LOAD
varies greatly depending on
the type of fan used. The simplest, inexpensive fans
contain no protection circuitry and input capacitance is on
the order of 200pF. More expensive fans generally incor-
porate a series-diode for reverse protection and input
DAC
The LTC1695 uses a 128-segment resistor ladder to
implement the monotonic 6-bit voltage DAC (Figure 3).
Guaranteeing monotonicity (no missing codes) permits
the use of the LTC1695 in thermal feedback control
applications. As the typical application uses a 5V supply
for V
CC,
the reference for the 6-bit DAC is V
CC
. LTC
recommends a 10
μ
F or greater tantalum capacitor to
bypass V
CC
. Users must account for the variation in the
DAC’s output absolute accuracy as V
CC
varies. V
CC
voltage
should not exceed the absolute maximum rating of 7V or
drop below the typical 2.8V undervoltage lockout thresh-
old (UVLO) during normal operation.
The LTC1695’s DAC specifications (INL, DNL, V
OS
) ac-
count for the offset and gain errors of the linear regulator
with respect to I
LOAD
. Consult the Definitions section for
more details.
The worst-case condition occurs if the LTC1695 P-chan-
nel pass transistor enters dropout at full-scale V
OUT
and
I
LOAD.
Full-scale V
OUT
(V
FS
) is 4.922V with V
CC
= 5V. In this
condition, loop gain drops and gain error increases. The
LTC1695 is designed for monotonicity up to V
FS
with DNL
and INL less than 0.75 LSB. Refer to the Electrical Char-
acteristics and Typical Performance Characteristics for
more information.
Figure 3. Ladder DAC
64 RESISTOR
VOLTAGE TABS
720
SWITCHES
V
CC
GND
REFERENCE
OP AMP
“000000” = 0V
“111111” = 0.984 V
CC
/2
6
SMBus
COMMAND
D5 to D0
V
CC
/2
1695 F03
APPLICATIO
S I
N
FOR
ATIO
U
W
U
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1695CS5#PBF | 制造商:Linear Technology 功能描述:DP-Other, CUT TAPE SMBus Fan Speed Controller |
| LTC1695CS5#TR | 功能描述:IC CTRLR FAN SPD SMBUS SOT23-5 RoHS:否 類別:集成電路 (IC) >> PMIC - 電機和風扇控制器，驅動器 系列:- 產(chǎn)品變化通告:ATA683(3,4)PLQW Obsolescence 09/Aug/2012 標準包裝:1 系列:- 應用:DC 電機控制器，無刷（BLDC），3 相 評估套件:可供 輸出數(shù):1 電流 - 輸出:100mA 電壓 - 負載:5.25 V ~ 20 V 電源電壓:5.25 V ~ 20 V 工作溫度:-40°C ~ 150°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應商設備封裝:48-VQFN（7x7） 包裝:剪切帶 (CT) 其它名稱:ATA6833-PLQWCT |
| LTC1695CS5#TRM | 功能描述:IC CTRLR FAN SPD SMBUS SOT23-5 RoHS:否 類別:集成電路 (IC) >> PMIC - 電機和風扇控制器，驅動器 系列:- 產(chǎn)品變化通告:ATA683(3,4)PLQW Obsolescence 09/Aug/2012 標準包裝:1 系列:- 應用:DC 電機控制器，無刷（BLDC），3 相 評估套件:可供 輸出數(shù):1 電流 - 輸出:100mA 電壓 - 負載:5.25 V ~ 20 V 電源電壓:5.25 V ~ 20 V 工作溫度:-40°C ~ 150°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應商設備封裝:48-VQFN（7x7） 包裝:剪切帶 (CT) 其它名稱:ATA6833-PLQWCT |
| LTC1695CS5#TRMPBF | 功能描述:IC CTRLR FAN SPD SMBUS SOT23-5 RoHS:是 類別:集成電路 (IC) >> PMIC - 電機和風扇控制器，驅動器 系列:- 產(chǎn)品變化通告:ATA683(3,4)PLQW Obsolescence 09/Aug/2012 標準包裝:1 系列:- 應用:DC 電機控制器，無刷（BLDC），3 相 評估套件:可供 輸出數(shù):1 電流 - 輸出:100mA 電壓 - 負載:5.25 V ~ 20 V 電源電壓:5.25 V ~ 20 V 工作溫度:-40°C ~ 150°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應商設備封裝:48-VQFN（7x7） 包裝:剪切帶 (CT) 其它名稱:ATA6833-PLQWCT |
| LTC1695CS5#TRPBF | 功能描述:IC CTRLR FAN SPD SMBUS SOT23-5 RoHS:是 類別:集成電路 (IC) >> PMIC - 電機和風扇控制器，驅動器 系列:- 產(chǎn)品變化通告:ATA683(3,4)PLQW Obsolescence 09/Aug/2012 標準包裝:1 系列:- 應用:DC 電機控制器，無刷（BLDC），3 相 評估套件:可供 輸出數(shù):1 電流 - 輸出:100mA 電壓 - 負載:5.25 V ~ 20 V 電源電壓:5.25 V ~ 20 V 工作溫度:-40°C ~ 150°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應商設備封裝:48-VQFN（7x7） 包裝:剪切帶 (CT) 其它名稱:ATA6833-PLQWCT |
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