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參數(shù)資料
| 型號： | MAX6781 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | 36/PLASTIC JS/DRIB/FLAT CAB/100 PAK |
| 中文描述： | 低功耗、精度達1%的電池監(jiān)測器，提供µDFN和SC70封裝 |
| 文件頁數(shù)： | 7/12頁 |
| 文件大?。?/td> | 221K |
| 代理商： | MAX6781 |
M
Low-Power, 1%-Accurate Battery
Monitors in μDFN and SC70 Packages
_______________________________________________________________________________________
7
The MAX6779, MAX6780, and MAX6781 monitor two
battery levels or two independent voltages. A common
application for this type of dual-battery monitor is to use
one output as an early warning signal and the other as
a dead-battery indicator.
Hysteresis
Input hysteresis defines two thresholds, separated by a
small voltage (the hysteresis voltage), configured so
the output asserts when the input falls below the falling
threshold, and deasserts only when the input rises above
the rising threshold. Figure 4 shows this graphically.
Hysteresis removes, or greatly reduces, the possibility of
the output changing state in response to noise or battery
terminal voltage recovery after load removal.
Fixed Hysteresis
The MAX6775/MAX6776/MAX6779/MAX6780/MAX6781
have factory-set hysteresis for ease of use, and reduce
component count. For these devices, the absolute hys-
teresis voltage is a percentage of the internally generat-
ed reference. The amount depends on the device
option. “A” devices have 0.5% hysteresis, “B” devices
have 5% hysteresis, and “C” devices have 10% hystere-
sis. Table 2 presents the threshold voltages for devices
with internally fixed hysteresis.
Adjustable Hysteresis
The MAX6777/MAX6778 offer external hysteresis con-
trol through the resistive divider that monitors battery
voltage. Figure 3 shows the connections for external
hysteresis. See the
Calculating an External Hysteresis
Resistive Divider
section for more information.
Applications Information
Resistor-Value Selection
Choosing the proper external resistors is a balance
between accuracy and power use. The input to the volt-
age monitor, while high impedance, draws a small cur-
rent, and that current travels through the resistive
divider, introducing error. If extremely high resistor val-
ues are used, this current introduces significant error.
With extremely low resistor values, the error becomes
negligible, but the resistive divider draws more power
from the battery than necessary and shortens battery
life. Figure 1 calculates the optimum value for R
H
using:
where e
A
is the maximum acceptable absolute resistive
divider error (use 0.01 for 1%), V
BATT
is the battery volt-
age at which
LBO
should activate, and I
L
is the worst-
case LBI leakage current. For example, with 0.5%
accuracy, a 2.8V battery minimum, and 5nA leakage,
R
H
= 2.80M
.
Calculate R
L
using:
where V
LBIF
is the falling threshold voltage from Table 2.
Continuing the above example, select V
LBIF
= 1.0998V
(10% hysteresis device) and R
L
= 1.81M
.
R
V
V
x R
V
BATT
L
LBIF
LBIF
H
=
R
e
x V
I
L
H
A
BATT
=
V
BATT
LBO
V
LBIR
V
LBIF
V
HYST
t
PD
t
PD
MAX6775
MAX6776
Figure 4. Hysteresis
Table 2. Typical Falling and Rising Thresholds for
MAX6775/MAX6776/MAX6779/MAX6780/MAX6781
DEVICE OPTION
PERCENT
HYSTERESIS (%)
FALLING THRESHOLD
(V
LBIF
) (V)
1.2159
1.1609
1.0998
RISING THRESHOLD
(V
LBIR
) (V)
1.222
1.222
1.222
HYSTERESIS VOLTAGE
(V
HYST
) (mV)
6.11
61.1
122
A
B
C
0.5
5
10
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX6781LTA+ | 制造商:Maxim Integrated Products 功能描述:VOLT SUPERVISOR MONITOR 1.222V 6PIN UDFN - Rail/Tube |
| MAX6781LTA+T | 功能描述:電池管理 Dual 1%-Accurate Battery Monitor RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
| MAX6781LTB+ | 制造商:Maxim Integrated Products 功能描述: 制造商:Rochester Electronics LLC 功能描述: |
| MAX6781LTB+T | 功能描述:電池管理 Dual 1%-Accurate Battery Monitor RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
| MAX6781LTC+ | 制造商:Maxim Integrated Products 功能描述:VOLT SUPERVISOR MONITOR 1.222V 6PIN UDFN - Rail/Tube 制造商:Rochester Electronics LLC 功能描述: |
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