www.ti.com
Hardware Low Power Design Guidelines
7
SPRAC74A–February 2017–Revised March 2017
Submit Documentation Feedback
Copyright © 2017, Texas Instruments Incorporated
AM335x Low Power Design Guide
2.2.2.1 Analog-to-Digital Converter (ADC)
If the ADC is unused, connect all the TSC_ADC signals to the same ground as the V
SS
terminals:
• VREFP
• VREFN
• AIN[7:0]
• VDDA_ADC
• VSSA_ADC
2.2.2.2 USB
If either USB0 or USB1 is unused, connect the respective VDDA1P8V_USB terminal to any 1.8-V power
supply and respective VDDA3P3V_USB terminal to any 3.3-V power supply. If the system does not have
a 3.3-V power supply, the VDDA3P3V_USB terminal may be connected to ground. The respective VBUS,
ID, DP, and DM terminals may be connected to ground or left floating. The CE pin should be left floating.
Since the USB PHYs are on by default, software needs to turn these interfaces off to maximize the power
savings.
2.2.2.3 RTC
If the RTC internal oscillator is not used, such as when an external LVCMOS clock is used, or if RTC is
not used, leave the unused RTC_XTAL pins open circuit, and connect VDD_RTC to VSS if using the ZCZ
package.
2.2.3 Wakeup and Deep Sleep Connections
AM335x has several peripherals in the Wakeup Power Domain. Since these peripherals remain powered
on during deep sleep and suspend, they can be used to generate wakeup interrupts when the processor is
in a suspend or sleep mode. In addition, these peripherals can be used to control on board peripherals
during the suspend/resume sequence.
Modules in the PD_WKUP domain include:
• GPIO0
• DMTIMER0_dmc
• DMTIMER1
• Inter-Integrated Circuit (I2C0)
• TSC
• WDT1
For a full list, see the Device Modules and Power Management Attributes List section in the AM335x and
AMIC110 Sitara™ Processors Technical Reference Manual.
GPIO0 is the only GPIO bank that can generate a wakeup interrupt, connect wakeup sources only to
GPIO0[0:31]. In addition, if DDR3 is used with a VTT regulator, route the enable signal to an output pin in
GPIO0 so that the processor can shut it off when in DS0.
For low power designs, consider using a crystal oscillator instead of a LVCMOS square wave clock. The
AM335x has internal circuitry that can entirely turn off the crystal during deep sleep (DS0). Similar
functionality with an external LVCMOS clock would require additional external circuitry.
The AM335x has a Cortex M3 that uses I2C0 to adjust voltages during DS0, so to take advantage of this
feature, make sure the PMIC is connected on the I2C0 bus.
To Next Page
Loading...
Need help?
General
