参数资料
型号: MAX6861UK41+T
厂商: Maxim Integrated Products
文件页数: 12/17页
文件大小: 0K
描述: IC MPU SUPERVISOR SOT23-5
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 2,500
类型: 简单复位/加电复位
监视电压数目: 1
输出: 推挽式,图腾柱
复位: 低有效
复位超时: 可调节/可选择
电压 - 阀值: 4.1V
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: 带卷 (TR)
Nanopower μP Supervisory Circuits with
Manual Reset and Watchdog Timer
Transient Immunity
In addition to issuing a reset to the μP during power-up,
power-down, and brownout conditions, the MAX6854/
MAX6855/MAX6856/MAX6858/MAX6860–MAX6869 are
relatively immune to short-duration supply transients, or
glitches. The Maximum V CC Transient Duration vs. Reset
Threshold Overdrive graph in the Typical Operating
Characteristics shows this relationship.
The area below the curve of the graph is the region in
which these devices typically do not generate a reset
pulse. This graph was generated using a falling pulse
applied to V CC , starting 100mV above the actual reset
threshold, V TH , and ending below this threshold (reset-
threshold overdrive). As the magnitude of the transient
increases, the maximum allowable pulse width
decreases. Typically, a 100mV V CC transient duration
of 40μs or less does not cause a reset.
Interfacing to Other Voltages for Logic
Compatibility
The open-drain RESET output can be used to interface
to a μP with other logic levels. As shown in Figure 4, the
open-drain output can be connected to voltages from 0
to 5.5V.
Generally, the pullup resistor connected to RESET con-
nects to the supply voltage that is being monitored at
the IC’s V CC input. However, some systems use the
open-drain output to level-shift from the monitored sup-
ply to reset circuitry powered by another supply voltage.
Keep in mind that as the supervisor’s V CC decreases,
so does the IC’s ability to sink current at RESET .
Ensuring a Valid RESET Down to V CC = 0V
(Push-Pull RESET )
When V CC falls below 1.1V, RESET ’s current-sinking
capability declines drastically. The high-impedance
CMOS logic inputs connected to RESET can drift to
undetermined voltages. This presents no problems in
most applications, since most μPs and other circuitry
do not operate with V CC below 1.1V.
In those applications where RESET must be valid down
to 0, add a pulldown resistor between RESET and GND
for the MAX6854/MAX6858/MAX6861/MAX6864/
MAX6867 push-pull outputs. The resistor sinks any stray
leakage currents, holding RESET low (Figure 5). Choose
a pulldown resistor that accommodates leakages, such
that RESET is not significantly loaded and is capable of
pulling to GND. The external pulldown cannot be used
with the open-drain reset outputs.
Watchdog Software Considerations
One way to help the watchdog timer monitor software
execution more closely is to set and reset the watchdog
1.8V
3.3V
V CC
V CC
V CC
MAX6856
MAX6860
MAX6863
MAX6866
MAX6869
100k ?
V CC
MAX6854
MAX6858
MAX6861
MAX6864
RESET
N
RESET
μ P
MAX6867
RESET
GND
GND
GND
2M ?
Figure 4. Interfacing with Other Voltage Levels
Figure 5. Ensuring RESET Valid to VCC = Ground
12
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