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MAX71020
Single-Chip Electricity Meter AFE
500
400
300
200
100
0
-100
During a power failure, as V 3P3A falls, two thresholds are
detected. The first threshold, at 3.0V, warns the host con-
troller that the analog modules are no longer accurate.
The second threshold, at 2.8V, warns the host controller
that a serious reduction in supply voltage has occurred
and that the reliability of OTP reads may be affected.
Reset Sequence
The MAX71020 does not provide automatic reset genera-
-200
-300
-400
-500
0
CURRENT [A]
VOLTAGE [V]
ENERGY PER INTERVAL [Ws]
ACCUMULATED ENERGY [Ws]
5 10 15
20
tion. The reset needs to be generated by the host con-
troller or by external circuitry connected to the RESETZ
pin. When the MAX71020 receives a reset signal, either
from the RESETZ pin or from the SPI (using a write to
the RESET register at address 0x322), it asynchronously
halts what it was doing. It then clears the RAM and
Figure 4. Voltage, Current, Momentary and Accumulated Energy
Figure 4 shows the shapes of V(t), I(t), the instantaneous
power and the accumulated energy resulting from 50
samples of the voltage and current signals over a period
of 20ms. The application of 240V AC and 100A results in
an accumulation of 480Ws (= 0.133Wh) over the 20ms
period, as indicated by the accumulated power curve. The
described sampling method works reliably, even in the
presence of dynamic phase shift and harmonic distortion.
After a sufficient number (typically 2520) of multiplexer
frames have been collected, the MAX71020 issues an
interrupt to the host using the INTZ pin, signalling that new
energy values are available.
Fault and Reset Behavior
Events at Power-Down
Power fault detection is performed by internal com-
parators that monitor the voltage at the V 3P3A pin and
also monitor the internally generated V DD pin voltage
(1.8V DC). V 3P3SYS and V 3P3A must be connected
together at the PCB level so that the comparators, which
are internally connected only to the V 3P3A pin, are able to
simultaneously monitor the common V 3P3SYS and V 3P3A
voltage. The following discussion assumes that V 3P3A
and V 3P3SYS are connected together at the PCB level.
Table 6. VSTAT[1:0]
invokes the Load Engine (LE). The LE initializes RAM and
hardware control registers from the CE code image that
is stored in OTP memory. Only RAM cells and hardware
registers that need not change dynamically are loaded.
All other RAM cells and registers have to be loaded by
the host controller. The LE automatically refreshes the
values of the registers it is tasked with loading during
the operation of the MAX71020. This refresh happens in
increments of one register at a time and at a rate of one
register per second.
An errant reset can occur during EMI events. If this hap-
pens, the host controller is notified. This is accomplished
by the holding the INTZ pin low until the host clears the
event (the F_RESET bit in the M_STAT register is set to
indicate that a reset has occurred).
Applications Information
Sensor Connection
Figure 5 to Figure 8 show voltage-sensing resistive
dividers, current-sensing current transformers (CTs) and
current-sensing resistive shunts and their proper connec-
tion to the voltage and current inputs of the MAX71020.
All input signals to the MAX71020 sensor inputs are volt-
age signals providing a scaled representation of either a
sensed voltage or current.
VSTAT[1:0]
00
01
11
Maxim Integrated
DESCRIPTION
System Power-OK. V V3P3A > 3.0V. Analog modules are functional and accurate.
System Power is low. 2.8V < V V3P3A < 3.0V. Analog modules not accurate.
System power below 2.8V. Ability to monitor power is about to fail.
16
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相关代理商/技术参数
MAX71020AEUI+R 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:Single-Chip Electricity Meter AFE
MAX710C/D 功能描述:直流/直流开关转换器 3.3V/5V or Adjustable Step-Up Step-Down DC-DC Converters RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
MAX710C/D DIE 制造商:Maxim Integrated Products 功能描述:
MAX710ESE 功能描述:直流/直流开关转换器 3.3/5V or Adjustable Step-Up Step-Down RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
MAX710ESE+ 功能描述:直流/直流开关转换器 3.3/5V or Adjustable Step-Up Step-Down RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
MAX710ESE+ 制造商:Maxim Integrated Products 功能描述:CONVERTOR DC/DC ((NW))
MAX710ESE+T 功能描述:直流/直流开关转换器 3.3/5V or Adjustable Step-Up Step-Down RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
MAX710ESE-T 功能描述:直流/直流开关转换器 3.3/5V or Adjustable Step-Up Step-Down RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT