ZEUS Technical Manual

Power and power management

 

 

COM Ports power management

RS232 transceivers can be placed in low power mode in case they are not used. This can reduce the power consumption of each RS232 transceiver down to 33 μW. GPIO pins 3 and 4 of Expander 2 (I2C address 0x22) are used to shut down COM1 and COM2. GPIO pin 1 of Expander 1 (I2C address 0x21) is used to shut down COM3.

EXP2_GPIO3 (U1_RS232_SHDN#)COM1 RS232 operation status

0

Shutdown mode

1

Normal operation

 

 

EXP2_GPIO4 (U2_RS232_SHDN#)COM2 RS232 operation status

 

 

0

Shutdown mode

1

Normal operation

 

 

EXP1_GPIO1 (U3_RS232_EN)COM3 RS232 operation status

 

 

0

RS232 Shutdown mode

 

(RS422/485 enabled)

1

Normal operation

 

 

Temperature sensor power management

The LM75A device can be set to operate in two modes: normal or shut-down. In normal operating mode, the temp-to-digital conversion is executed every 100ms and the Temp register is updated at the end of each conversion. In shut-down mode, the device becomes idle, data conversion is disabled and the Temp register holds the latest result. However, the device I2C interface is still active and register write/ read operation can be performed. The device operating mode is controllable by programming bit B0 of the configuration register. The temperature conversion is initiated when the device is powered-up or put back into normal mode from shut-down. The power consumption in shut-down mode is near zero (11.5μW).

For more information about power management, refer to the LM75A datasheet on the Development Kit CD.

I/O expander power management

When the serial I2C interface is idle and the PWM intensity control is unused, the MAX7313 automatically enters standby mode. If the PWM intensity control is used, the operating current is slightly higher because the internal PWM oscillator is running. The power consumption in standby mode (with PWM disabled) is near zero (4μW).

Configuration PROM power management

When the serial I2C interface is idle the 24AA01 automatically enters standby mode. The power consumption in standby mode is near zero (3.3μW).

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