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参数资料
| 型号： | MIC2777-31YM5 TR |
| 厂商： | Micrel Inc |
| 文件页数： | 6/8页 |
| 文件大小： | 0K |
| 描述： | IC SUPERVISOR DUAL MCPWR SOT23-5 |
| 标准包装： | 1 |
| 类型： | 多压监控器 |
| 监视电压数目： | 2 |
| 输出： | 补充型 |
| 复位： | 高有效/低有效 |
| 复位超时： | 最小为 140 ms |
| 电压 - 阀值： | 3.09V，可调 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | SC-74A，SOT-753 |
| 供应商设备封装： | SOT-23-5 |
| 包装： | 标准包装 |
| 产品目录页面： | 1112 (CN2011-ZH PDF) |
| 其它名称： | 576-2688-6 |
( R1 + R2 )
V TH = V REF ×
( R TOTAL ) ( V REF )
V TH
V CORE(min) 0.950
1.025
1.025
MIC2777
Application Information
Programming the Voltage Threshold
Referring to the “Typical Application Circuit”, the voltage
threshold on the IN pin is calculated as follows:
R2
where V REF = 0.300V
In order to provide the additional criteria needed to solve
for the resistor values, the resistors can be selected such
that the two resistors have a given total value, that is, R1
+ R2 = R TOTAL . Imposing this condition on the resistor val-
ues provides two equations that can be solved for the two
unknown resistor values. A value such as 1MΩ for R TOTAL
is a reasonable choice since it keeps quiescent current to a
generally acceptable level while not causing any measurable
errors due to input bias currents. The larger the resistors, the
larger the potential errors due to input bias current (I IN ). The
maximum recommended value of R TOTAL is 3MΩ.
Applying this criteria and rearranging the V TH expression to
solve for the resistor values gives:
R2 =
R1 = R TOTAL – R2
Application Example
Figure 1 illustrates a hypothetical MIC2777-23 application
in which the MIC2777-23 is used to monitor the core and
I/O supplies of a high-performance CPU or DSP. The core
supply, V CORE , in this example is 1.0V ±5%. The main power
rail and I/O voltage, V I/O , is 2.5V ±5%. As shown in Figure 1,
the MIC2777 is powered by V I/O . The minimum value of V I/O
is 2.5V –5% = 2.375V; the maximum is 2.5V +5% = 2.625V.
This is well within the MIC2777’s power supply range of
1.5V to 5.5V.
Resistors R1 and R2 must be selected to correspond to the
V CORE supply of 1.0V. The goal is to insure that the core
supply voltage is adequate to insure proper operation, i.e.,
V CORE ≥ (1.0V –5%) = 0.950V. Because there is always a
small degree of uncertainty due to the accuracy of the resis-
tors, variations in the devices’ voltage reference, etc., the
threshold will be set slightly below this value. The potential
variation in the MIC2777’s input voltage reference (V REF ) is
speci?ed as ±1.5%. The resistors chosen will have their own
tolerance speci?cation. This example will assume the use of
1% accurate resistors. The potential worst-case error contri-
bution due to input bias current can be calculated once the
resistor values are chosen. If the guidelines above regarding
the maximum total value of R1+R2 are followed, this error
contribution will be very small thanks to the MIC2777’s very
low input bias current.
Micrel, Inc.
To summarize, the various potential error sources are:
? Variation in V REF : speci?ed at ±1.5%
? Resistor tolerance: chosen by designer (typically ≤
±1%)
? Input bias current, I IN : calculated once resistor values
are known, typically very small
Taking the various potential error sources into account, the
threshold voltage will be set slightly below the minimum V CORE
speci?cation of 0.950V so that when the actual threshold
voltage is at its maximum, it will not intrude into the normal
operating range of V CORE . The target threshold voltage will
be set as follows:
Given that the total tolerance on V TH for the IN pin is [V REF
tolerance] + [resistor tolerance]
= ±1.5% + ±1% = ±2.5%,
and V TH(max) = V CORE(min) ,
then V CORE(min) = V TH + 2.5% V TH = 1.025 V TH ,
therefore, solving for V TH results in
V TH = = = 0.9268V
Solving for R1 and R2 using this value for V TH and the equa-
tions above yields:
R1 = 676.3kΩ ≈ 673kΩ
R2 = 323.7kΩ ≈ 324kΩ
The resulting circuit is shown in Figure 1.
Input Bias Current Effects
Now that the resistor values are known, it is possible to cal-
culate the maximum potential error due to input bias current,
I IN . As shown in the “Electrical Characteristics” table, the
maximum value of I IN is 10nA. (Note that the typical value
is a much smaller 5pA) The magnitude of the offset caused
by I IN is given by:
V ERROR = I IN(max) × (R1||R2) =
V ERROR = ±1 × 10 -8 A × 2.189 ×10 5 ? =
V ERROR = ±2.189 × 10 -3 V =
V ERROR = ±2.189mV
The typical error is about three orders of magnitude lower
than this– close to one microvolt! Generally, the error
due to input bias can be discounted. If it is to be taken
into account, simply adjust the target threshold voltage
downward by this amount and recalculate R1 and R2. The
resulting value will be very close to optimum. If accuracy
is more important than the quiescent current in the
resistors, simply reduce the value of R TOTAL to minimize
offset errors.
MIC2777
6
November 2005
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC2777-44BM5 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| MIC2777-44BM5 TR | 功能描述:IC SUPERVISOR DUAL MCPWR SOT23-5 RoHS:否 类别:集成电路 (IC) >> PMIC - 监控器 系列:- 标准包装:1 系列:- 类型:简单复位/加电复位 监视电压数目:1 输出:开路漏极或开路集电极 复位:低有效 复位超时:标准传输延迟为 60 µs 电压 - 阀值:3V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SC-74A，SOT-753 供应商设备封装:SOT-23-5 包装:Digi-Reel® 其它名称:LM8364BALMF30DKR |
| MIC2777-44BM5TR | 制造商:Rochester Electronics LLC 功能描述:- Tape and Reel |
| MIC2777-44YM5 TR | 功能描述:监控电路 Dual Voltage Supervisor with 0.3V and 4.43V Thresholds, Active-High and Active-Low Push-Pull Outputs, 140ms Reset Pulse, Manual Reset, SOT23-5 (Lead Free) RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel |
| MIC2777-46BM5 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
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