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參數(shù)資料
| 型號(hào)： | MAX1729 |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類： | 數(shù)字信號(hào)處理 |
| 英文描述： | Replaced by TMS320VC5506 : Digital Signal Processors 100-LQFP 0 to 0 |
| 中文描述： | ECB及LCD偏置電源，帶有精確的輸出電壓及溫度補(bǔ)償 |
| 文件頁(yè)數(shù)： | 9/12頁(yè) |
| 文件大小： | 158K |
| 代理商： | MAX1729 |
2) Given the maximum output voltage (V
MAX
) and mini-
mum output voltage (V
MIN
), calculate values for R3 and
R4 as follows:
3) For first-order temperature compensation, calculate
R5 as shown below. (If temperature compensation is
not used, leave R5 open.)
where Tempco is the negative temperature coefficient
needed to compensate the ECB or LCD display for
changes in temperature.
4) Solve for V
COMP
. The duty cycle used here corre-
sponds to the duty cycle that yields the maximum out-
put voltage, not including first-order temperature
compensation.
where a 90% duty cycle corresponds to Duty Cycle = 0.9.
5) Use the results from the above calculations to solve
for R2. (For applications not utilizing temperature com-
pensation, use 1 / R5 = 0.)
External Component Value Example
The example application requires the output voltage to
adjust between 5V and 10V, using the circuit shown in
Figure 3. The device in our example needs a tempera-
ture coefficient of 33mV/°C, which yields the following
results.
1) V
MAX
= 10V and I
FB
= 29.24μA is within the limits
and yields a reasonable resistor value, therefore:
2) V
MAX
= 10V and V
MIN
= 5V, therefore:
300k
=
with R3 = 36.7k
, then V
MIN
= 5.019V. Let R4 =
R3 = 36.7k
.
3) Tempco = 33mV/°C, therefore:
4) If external circuitry limits the duty cycle to 90%, the
following equation is true:
5) Solving for R2:
With R2 = 56k
, a duty cycle of 87.4% generates a
V
OUT
of 10V.
Component S elec tion
Inductors
Use a 220μH inductor to maximize output current
(2.5mA typical). Use an inductor with DC resistance
less than 10
and a saturation current exceeding
35mA. For lower peak inductor current, use a 470μH
inductor with DC resistance less than 20
and a satu-
ration current over 18mA. This limits output current to
typically less than 1mA. See Table 1 for a list of recom-
mended inductors. The inductor should be connected
from the battery to the LX pin, as close to the IC as pos-
sible.
Capacitors
The equivalent series resistance (ESR) of output capac-
itor C2 directly affects output ripple. To minimize output
ripple, use a low-ESR capacitor. A physically smaller
capacitor, such as a common ceramic capacitor, mini-
mizes board space and cost while creating an output
ripple that’s acceptable in most applications. Refer to
Table 2 for recommended capacitor values.
1
R2
V
R1
V
R3
V
R5
1
V
1
R1
1
R3
1
R5
1
56560
OUT
COMP
FB
FB
=
+
+
+
+
=
V
1.228 1
0.9
2
0.6754V
COMP
=
=
R5
300k
33mV/ C
=
°
=
/
16. mV
5
k
150
C
R3
1/2
5V
1.228
36,840
=
R1
10V
1.228V
29.24 A
=
=
300k
1
R2
1
V
V
R1
V
R3
V
R5
1
R1
1
R3
1
R5
FB
OUT
COMP
FB
=
+
+
+
+
V
=V
1 ± Duty Cycle
R4
+
R3
R4
COMP
FB
R5 =
R1
Tempco
16.5mV/ C
R3 = 1/2
R1
± V
V
V
R4 = R3
MAX
MIN
FB
M
ECB and LCD Display Bias Supply with Accurate
Output Voltage and Temperature Compensation
_______________________________________________________________________________________
9
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參數(shù)描述 |
|---|---|
| MAX1729EUB | 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 ECB & LCD Display Bias Supply RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| MAX1729EUB-T | 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 ECB & LCD Display Bias Supply RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| MAX172ACNG | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC Integrated Circuits (ICs) RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| MAX172ACNG+ | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC 12-Bit 100ksps 5.25V- Precision ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
| MAX172ACWG | 功能描述:模數(shù)轉(zhuǎn)換器 - ADC RoHS:否 制造商:Texas Instruments 通道數(shù)量:2 結(jié)構(gòu):Sigma-Delta 轉(zhuǎn)換速率:125 SPs to 8 KSPs 分辨率:24 bit 輸入類型:Differential 信噪比:107 dB 接口類型:SPI 工作電源電壓:1.7 V to 3.6 V, 2.7 V to 5.25 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-32 |
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