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| 型号： | MAX792TESE+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 8/16页 |
| 文件大小： | 0K |
| 描述： | IC SUPERVISOR MPU 16-SOIC |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| 类型： | 简单复位/加电复位 |
| 监视电压数目： | 1 |
| 输出： | 推挽式，推挽式 |
| 复位： | 高有效/低有效 |
| 复位超时： | 最小为 140 ms |
| 电压 - 阀值： | 3.06V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 16-SOIC |
| 包装： | 管件 |
Microprocessor and Nonvolatile
Memory Supervisory Circuits
Detailed Description
Manual-Reset Input
Many μP-based products require manual-reset capabil-
ity, allowing the operator to initiate a reset. The manu-
al/external-reset input ( MR) can connect directly to a
switch without an external pull-up resistor or debounc-
ing network. MR internally connects to a 1.30V com-
parator, and has a high-impedance pull-up to V CC , as
shown in Figure 1. The propagation delay from assert-
ing MR to reset asserted is typically 12μs. Pulsing MR
low for a minimum of 25μs asserts the reset function
(see Reset Function section). The reset output remains
active as long as MR is held low, and the reset timeout
period begins after MR returns high (Figure 2). To pro-
vide extra noise immunity in high-noise environments,
pull MR up to V CC with a 100k ? resistor.
Use MR as either a digital logic input or as a second low-
line comparator. Normal TTL/CMOS levels can be
wire-OR connected via pull-down diodes (Figure 3),
and open-drain/collector outputs can be wire-ORed
directly.
Monitoring the Regulated Supply
The MAX792/MAX820 offer two modes for monitoring
the regulated supply and providing reset and non-
maskable interrupt (NMI) signals to the μP: internal
threshold mode uses the factory preset low-line and
reset thresholds, and external programming mode
allows the low-line and reset thresholds to be pro-
grammed externally using a resistor voltage divider
(Figure 4).
Internal Threshold Mode
Connecting the reset-input/internal-mode select pin
(RESET IN/ INT ) to ground selects internal threshold
mode (Figure 4a). In this mode, the low-line and reset
thresholds are factory preset by an internal voltage
divider (Figure 1) to the threshold voltages specified in
the Electrical Characteristics (Reset Threshold Voltage
and Low-Line Threshold Voltage). Connect the low-line
output ( LOWLINE ) to the μP NMI pin, and connect the
active-high reset output (RESET) or active-low reset
output ( RESET ) to the μP reset input pin.
Additionally, the low-line input/reference-output pin
(LLIN/REFOUT) connects to the internal 1.30V refer-
ence in internal threshold mode. Buffer LLIN/REFOUT
with a high-impedance buffer to use it with external
circuitry. In this mode, when V CC is falling, LOWLINE is
guaranteed to be asserted prior to reset assertion.
External Programming Mode
Connecting RESET IN/ INT to a voltage above 600mV
selects external programming mode. In this mode, the
low-line and reset comparators disconnect from the inter-
nal voltage divider and connect to LLIN/REFOUT and
RESET IN/ INT , respectively (Figure 1). This mode allows
flexibility in determining where in the operating voltage
range the NMI and reset are generated. Set the low-line
and reset thresholds with an external resistor divider, as in
Figure 4b or Figure 4c. RESET typically remains valid for
V CC down to 2.5V; RESET is guaranteed to be valid with
V CC down to 1V.
Calculate the values for the resistor voltage divider in
Figure 4b using the following equations:
1) R3 = (1.30 x V CC MAX)/(V LOW LINE x I MAX )
2) R2 = [(1.30 x V CC MAX)/(V RESET x I MAX )] - R3
3) R1 = (V CC MAX/I MAX ) - (R2 + R3).
First choose the desired maximum current through the
voltage divider (I MAX ) when V CC is at its highest (V CC
MAX). There are two things to consider here. First, I MAX
contributes to the overall supply current for the circuit, so
you would generally make it as small as possible.
Second, I MAX cannot be too small or leakage currents will
adversely affect the programmed threshold voltages; 5μA
is often appropriate. Determine R3 after you have chosen
I MAX . Use the value for R3 to determine R2, then use both
R2 and R3 to determine R1.
For example, to program a 4.75V low-line threshold and a
4.4V reset threshold, first choose I MAX to be 5μA when
V CC = 5.5V and substitute into equation 1.
R3 = (1.30 x 5.5)/(4.75 x 5E-6) = 301.05k ? .
301k ? is the nearest standard 0.1% value. Substitute
into equation 2:
R2 = [(1.30 x 5.5)/(4.4 x 5E-6)] - 301k ? = 23.95k ? .
The nearest 0.1% resistor value is 23.7k ? . Finally, sub-
stitute into equation 3:
R1 = (5.5/5E-6) - (23.7k ? + 301k ? ) = 775k ? .
The nearest 0.1% value resistor is 787k ? . Determine the
actual low-line threshold by rearranging equation 1 and
plugging in the standard resistor values. The actual low-
line threshold is 4.75V and the actual reset threshold is
4.40V. An additional resistor allows the MAX792/MAX820
to monitor the unregulated supply and provide an NMI
before the regulated supply begins to fall (Figure 4c).
Both of these thresholds will vary from circuit to circuit
with resistor tolerance, reference variation, and compara-
tor offset variation. The initial thresholds for each circuit
will also vary with temperature due to reference and off-
set drift. For highest accuracy, use the MAX820.
8
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX792TESE+ | 功能描述:监控电路 MPU & NV Memory Supervisor 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 |
| MAX792TESE+T | 功能描述:监控电路 MPU & NV Memory Supervisor 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 |
| MAX792TESE-T | 功能描述:监控电路 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 |
| MAX792TMJE | 功能描述:监控电路 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 |
| MAX793RCPE | 功能描述:监控电路 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 |
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