Understanding LPC1752 Power-Down Mode-EEWORLD

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LPC1752 has four low power modes: sleep mode, deep sleep mode, power down mode, and deep power down mode. When the CPU is running in low power mode, you cannot use Jlink to download the program. It prompts that you cannot connect to JTAG or cannot use the debug mode. You need to wake up before you can download or burn. After downloading the program, you need to turn off the power and then turn it on again for the program to run normally.

After program debugging, sleep mode, deep sleep mode, and power-down mode can be awakened by any external interrupts such as GPIO interrupts and timer interrupts. In deep power-down mode, the internal RTC needs to be powered and the ISP pin P2.10 needs to be pulled low to wake up the CPU, otherwise the program cannot be downloaded.

Deep sleep mode saves more power than power-down mode, with a standby current of 10uA.

Another discovery is that although all pins are in high impedance state in sleep mode, deep sleep mode, and power-down mode, setting the specified pin low before entering low power mode remains valid.

The environment I tested was LPC1752. When no peripherals were connected, the standby current was less than 1mA. Two pins were connected to relays and 6 pins were connected to LCD. When the low power mode was entered without setting these pins low, the standby current reached 45mA. After testing, it was found that the relay current reached 35mA, the LCD current reached 6mA, and other analog circuits accounted for 4mA. Before entering the low power mode, these pins were cleared first, and then entered the low power state, and it was found that the standby current was less than 4mA (only the analog circuit and CPU).

After consulting the "CORTEX_M3 Technical Manual", it was found that when entering low power mode, the CPU does not need to push the stack register operation.

Keywords：LPC1752 Reference address：Understanding LPC1752 Power-Down Mode

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