Other Parts Discussed in Thread: MSP430F2274
Hi,
In LPM3 during which:
- Low-power mode 3 (LPM3)
– CPU is disabled.
– MCLK and SMCLK are disabled.
– DCO dc-generator is disabled.
– ACLK remains active.
We would only have running ACLK, and in many MSP430 example routines timer_A is configured to use ACLK as input source and wake up MCU at its interrupts. In this case for most of the time CPU clock off.
But does the peripherals consume power in LPM3? Most of the peripherals can be sourced from ACLK, including
|
Timer_A |
TASSELx Bits 9-8 Timer_A clock source select 00 TACLK 01 ACLK 10 SMCLK 11 INCLK (INCLK is device-specific and is often assigned to the inverted TBCLK) (see the device-specific data sheet) |
|
Timer_B |
TBSSELx Bits 9-8 Timer_B clock source select. 00 TBCLK 01 ACLK 10 SMCLK 11 INCLK (INCLK is device-specific and is often assigned to the inverted TBCLK) (see the device-specific data sheet) |
|
ADC10 |
ADC10CTL1.ADC10SSELx Bits 4-3 ADC10 clock source select 00 ADC10OSC 01 ACLK 10 MCLK 11 SMCLK |
|
WDT+ |
WDTCTL.WDTSSEL Bit 2 Watchdog timer+ clock source select 0 SMCLK 1 ACLK |
|
USCI A & B |
UCSSELx Bits 7-6 USCI clock source select. These bits select the BRCLK source clock. 00 UCLKI 01 ACLK 10 SMCLK 11 SMCLK |
The datasheet of MSP430F2274, page 29, Low-Power-Mode Supply Currents (Into V CC ) Excluding External Current, defines in footnote (1) that the current values are measured when
“All inputs are tied to 0 V or VCC . Outputs do not source or sink any current.”
But what about the internal possibly running peripherals clocked by ACLK? How much power/current does Timer_A, Timer_B, ADC10, WDT+, USCI A & B consume if they are all running, even without driving or sampling I/O pins (like isolated in the “internal” world of the SoC)?
In addition, as shown in SLAU144I, MSP430x2xx Family User's Guide SLAU144I, even ACLK itself can be sourced from 12KHz VLOCLK, LFXT1CLK, LFXT1 Oscillator, XT2 or DCOCLK. Apparently the higher frequency, the larger power/current consumption there would be.
I understand that it is difficult to define and measure exactly peripheral power consumption because it is predominantly determined by board layout and external components, as well as other factors such as how fast the USCI SPI/I2C are running at. But in LPM3, at least USCI would not be running (please correct me if wrong here), and how much current would each of the possible running peripheral sourced by ACLK drain, and most importantly the timer modules which are/is used to wake up CPU?
Matt
