参数资料
型号: MAX6784TCC+T
厂商: Maxim Integrated Products
文件页数: 13/17页
文件大小: 0K
描述: IC BATT MON TRPL 10% 12TQFN
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 2,500
功能: 电池监控器
电池化学: 碱性,锂离子,镍镉,镍金属氢化物
电源电压: 1.2 V ~ 5.5 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 12-TQFN 裸露焊盘
供应商设备封装: 12-TQFN-EP(4x4)
包装: 带卷 (TR)
Low-Power, 1% Accurate, Dual-/Triple-/Quad-Level
Battery Monitors in Small TDFN and TQFN Packages
R 3 = A REF
Reference Output
The reference output can provide up to 1mA of output
current. The output is not buffered. Excessive loading
affects the accuracy of the thresholds. An external
capacitor is not required for stability and is stable for
capacitive loads up to 50pF. In applications where the
load or the supply can experience step changes, a
capacitor reduces the amount of overshoot (under-
shoot) and improves the circuit’s transient response.
Place the capacitor as close to the device as possible
for best performance.
old (V INF ) on the associated IN_ (the rising threshold
(V INR ) is fixed). See Table 2. Calculate R 3 using:
e × V
I L
where e A is the fraction of the maximum acceptable
absolute resistive divider error attributable to the input
leakage current (use 0.01 for 1%), V REF is the refer-
ence output voltage, and I L is the worst-case HADJ_
leakage current. Calculate R 4 using:
Applications Information
Resistor-Value Selection
R 4 =
V INF × R 3
V REF ? V INF
Hysteresis ( % ) = 100 × INR INF
R 1 = A BATT
R 1 = A BATT
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. See Figure 6 and calculate the optimum value for
R1 using:
e × V
I L
where e A is the fraction of the maximum acceptable
absolute resistive divider error attributable to the input
leakage current (use 0.01 for 1%), V BATT is the battery
voltage at which LBO should activate, and I L is the
where V INF is the desired falling voltage threshold. To
calculate the percent hysteresis, use:
V ? V
V INR
where V INR is the rising voltage.
Calculating an External
Hysteresis Resistive Divider
(MAX6786/MAX6787/MAX6788)
Setting the hysteresis externally requires calculating
three resistor values, as indicated in Figure 2. First cal-
culate R 1 using:
e × V
I L
and R 20 using:
worst-case IN_ leakage current, from the Electrical
Characteristics. For example, for 0.5% error, a 2.8V
battery minimum, and 5nA leakage, R 1 = 2.80M ? .
R 20 =
V TH × R 1
V BATT ? V TH
( as in the above example )
R 2 =
I TOTAL =
R HYST = HYST
Calculate R 2 using:
V INF × R 1
V BATT ? V INF
where V INF is the falling threshold voltage from Table 2.
Continuing the above example, and selecting V INF =
0.5477V (10% hysteresis device), R 2 = 681k ? . There
are other sources of error for the battery threshold,
including resistor and input monitor tolerances.
Calculating an External Hysteresis
Resistive Divider (MAX6782–MAX6785)
To set the hysteresis, place a resistive divider from REF
to HADJ_ as shown in Figure 6. The resistive divider
sets voltage on HADJ_, which controls the falling thresh-
where R 20 = R 2 + R HYST determine the total resistive-
divider current, I TOTAL , at the trip voltage using:
V BATT
R 1 + R 20
Then, determine R HYST using:
V
I TOTAL
where V HYST is the required hysteresis voltage.
Finally, determine R 2 using:
R 2 = R 20 - R HYST
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