MAX6652监控系统结合电压监测与温度传感-MAX6652

Monitored Voltage	MAX6652 Input	Nominal Output Code	-5% Limit	+5% Limit
12	12VIN	192	182	201
5	3.3VIN (attenuated)	192	182	201
3.3	VCC (5VIN)	126	120	133
2.5	2.5VIN	192	182	201

Example 3: Low-voltage system.

VCC = 3.3V; monitored voltages are 5V, 3.3V, 2.5V, and 1.8V.
The 3.3V supply voltage can be monitored as in Example 2.

The 12VIN pin is available for monitoring the 5V supply. With 5V applied to this input, the output code will be as follows:

192 × 5/12 = 80

For alarms 5% above and below the 5V nominal power-supply voltage, we have the following:

high limit = 192 × 5V/12V × 1.05 = 84

and

low limit = 192 × 5V/12V × 0.95 = 76

The 3.3VIN pin will be used for monitoring the 1.8V supply voltage. With 1.8V applied to this input, the output code (rounded down) will be as follows:

192 × 1.8/3.3 = 104

For alarms 5% above and below the 1.8V nominal power-supply voltage, we have (rounded down):

high limit = 192 × 1.8V/3.3V × 1.05 = 109

and

low limit = 192 × 1.8V/3.3V × 0.95 = 99

The 2.5V input limits are the same as in the first two examples.


Figure 3. Circuit of Example 3. This circuit is used in a low-voltage system to monitor 5V, 3.3V, 2.5V, and 1.8V. The MAX6652 operates from a 3.3V supply. The 12VIN input monitors the 5V supply, and the 3.3VIN input monitors the 1.8V supply.

Table 3. Output Codes and ±5% Limits for the MAX6652 in a Low-Voltage System, Monitoring 5V, 3.3V, 2.5V, and 1.8V

Monitored Voltage	MAX6652 Input	Nominal Output Code	-5% Limit	+5% Limit
5	12VIN	80	76	84
3.3	VCC (5VIN)	126	120	133
2.5	2.5VIN	192	182	201
1.8	3.3VIN	104	99	109

Example 4: Alternative low-voltage system.

VCC = 3.3V; monitored voltages are 5V, 3.3V, 2.5V, and 1.8V.
This is an alternative to Example 3. In this example, the1.8V supply is monitored at the 2.5VIN input instead of at the 3.3VIN input, and the 2.5V supply is monitored at the 3.3VIN input. This improves the measurement resolution for the 1.8V supply, while making the resolution for the 2.5V supply somewhat worse relative to Example 3.

The 3.3V supply voltage is monitored as in Examples 2 and 3.

The 12VIN pin monitors the 5V supply as in Example 3.

The 3.3VIN pin will be used for monitoring the 2.5V supply voltage. With 2.5V applied to this input, the output code (rounded down) will be as follows:

192 × 2.5/3.3 = 145

For alarms 5% above and below the 2.5V nominal power-supply voltage, we have (rounded down):

high limit = 192 × 2.5V/3.3V × 1.05 = 152

and

low limit = 192 × 2.5V/3.3V × 0.95 = 138

The 2.5VIN pin will be used for monitoring the 1.8V supply voltage. With 1.8V applied to this input, the output code (rounded down) will be as follows:

192 × 1.8/2.5 = 138

For alarms 5% above and below the 2.5V nominal power-supply voltage, we have (rounded down):

high limit = 192 × 1.8/2.5 × 1.05 = 145

and

low limit = 192 × 1.8/2.5 × 0.95 = 131

Figure 4. Circuit of Example 4. This circuit is an alternative to the low-voltage circuit in Example 3. Monitored voltages are still 5V, 3.3V, 2.5V, and 1.8V, but the inputs to the 3.3VIN and 2.5VIN pins are swapped to give better resolution when measuring the 1.8V supply.

Table 4. Output Codes and ±5% Limits for the MAX6652 in the Alternative Low-Voltage System, Monitoring 5V, 3.3V, 2.5V, and 1.8V
Note that the 1.8V input voltage produces a larger ADC code, resulting in a higher-resolution measurement.

Monitored Voltage	MAX6652 Input	Nominal Output Code	-5% Limit	+5% Limit
5	12VIN	80	76	84
3.3	VCC (5VIN)	126	120	133
2.5	3.3VIN	145	138	152
1.8	2.5VIN	138	131	145