参数资料
型号: MCP121T-270E/LB
厂商: Microchip Technology
文件页数: 12/28页
文件大小: 0K
描述: IC SUPERVISOR 2.63V LOW SC-70
标准包装: 3,000
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: 最小为 80 ms
电压 - 阀值: 2.63V
工作温度: -40°C ~ 125°C
安装类型: 表面贴装
封装/外壳: SC-70,SOT-323
供应商设备封装: SC-70-3
包装: 带卷 (TR)
MCP102/103/121/131
4.0
APPLICATION INFORMATION
4.1
RST Operation
For many of today’s microcontroller applications, care
must be taken to prevent low-power conditions that can
cause many different system problems. The most
common causes are brown-out conditions, where the
system supply drops below the operating level momen-
tarily. The second most common cause is when a
slowly decaying power supply causes the
microcontroller to begin executing instructions without
sufficient voltage to sustain volitile memory (RAM), thus
producing indeterminate results. Figure 4-1 shows a
typical application circuit.
The MCP102/103/121/131 are voltage supervisor
devices designed to keep a microcontroller in reset
until the system voltage has reached and stabilized at
the proper level for reliable system operation. These
devices also operate as protection from brown-out
conditions.
V DD
The RST output pin operation determines how the
device can be used and indicates when the system
should be forced into reset. To accomplish this, an
internal voltage reference is used to set the voltage trip
point (V TRIP ). Additionally, there is a hysteresis on this
trip point.
When the falling edge of V DD crosses this voltage
threshold, the reset power-down timer (T RPD ) starts.
When this delay timer times out, the RST pin is forced
low.
When the rising-edge of V DD crosses this voltage
threshold, the reset power-up timer (T RPU ) starts.
When this delay timer times out, the RST pin is forced
high, T RPU is active and there is additional system
current.
The actual voltage trip point (V TRIPAC ) will be between
the minimum trip point (V TRIPMIN ) and the maximum
trip point (V TRIPMAX ). The hysteresis on this trip point
and the delay timer (T RPU ) are to remove any “jitter”
0.1
μF
V DD
MCP1XX
RST
V SS
R PU
V DD
PICmicro ?
Microcontroller
MCLR
(Reset input)
(Active-low)
V SS
that would occur on the RST pin when the device V DD
is at the trip point.
Figure 4-2 shows the waveform of the RST pin as deter-
mined by the V DD voltage, while Table 4-1 shows the
state of the RST pin. The V TRIP specification is for falling
V DD voltages. When the V DD voltage is rising, the RST
will not be driven high until V DD is at V TRIP + V HYS . Once
V DD has crossed the voltage trip point, there is also a
minimal delay time (T RPD ) before the RST pin is driven
low.
Note 1: Resistor R PU may be required with the
MCP121 due to the open-drain output.
TABLE 4-1:
RST PIN STATES
Resistor R PU may not be required with
State of RST Pin when:
the MCP131 due to the internal pull-up
resistor. The MCP102 and MCP103 do
not require the external pull-up resistor.
Device
V DD < V TRIP V DD >
V TRIP + V HYS
Ouput Driver
FIGURE 4-1:
Typical Application Circuit.
MCP102
MCP103
MCP121
MCP131
L
L
L
L
H
H
(1)
H
H (2)
Push-pull
Push-pull
Open-drain (1)
Open-drain (2)
Note 1: Requires External Pull-up resistor
2: Has Internal Pull-up resistor
V DD
V TRIPMAX
V TRIPMIN
V TRIPAC + V HYSAC
V TRIPAC
V TRIPAC
1V
RST
t RPD
< 1V is outside the
device specifications
t RPU
t RPD
t RPU
FIGURE 4-2:
DS21906B-page 12
RST Operation as Determined by the V TRIP and V HYS .
? 2005 Microchip Technology Inc.
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