TMS320VC5505 datasheet(39/135 Pages) TI

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TMS320VC5505

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SPRS503B – JUNE 2009 – REVISED JANUARY 2010

4.2

Power Considerations

The VC5505 provides several means of managing power consumption.

To minimize power consumption, the VC5505 divides its circuits into eight main isolated supply domains:

•

ANA_LDOI (LDO and Bandgap Power Supply)

•

Analog POR and PLL (VDDA_ANA and VDDA_PLL)

•

RTC (CVDD_RTC)

•

Digital Core (CVDD)

•

USB Core (USB_ VDD1P3 and USB_VDDA1P3)

•

USB PHY and USB PLL (USB_VDDOSC, USB_VDDA3P3, and USB_VDDPLL)

•

EMIF I/O (DVDDEMIF)

•

RTC I/O (DVDDRTC)

•

Rest of the I/O (DVDDIO)

4.2.1

LDO Configuration

The VC5505 includes one Low-Dropout Regulator (LDO) which can be used to regulate the supplies of

the analog PLL and SAR ADC.

4.2.1.1

Analog LDO

The ANA_LDOI pin (B12) provides the power to the Analog LDO, the bandgap reference generator, and

some I/O input pins and can range from 1.8 V to 3.6 V. The Bandgap provides accurate voltage and

current references to the POR, LDO, PLL, and SAR; therefore, for proper device operation, power must

always be applied to the ANA_LDOI pin. ANA_LDOO is regulated to 1.3 V and can optionally be used to

provide up to 3 mA to the VDDA_ANA (Power Management Voltage Supervisor and SAR VDD power inputs)

and VDDA_PLL (System PLL power input).

4.3

Clock Considerations

The system clock, which is used by the CPU and most of the DSP peripherals, is controlled by the system

clock generator. The system clock generator features a software-programmable PLL multiplier and several

dividers. The clock generator accepts an input reference clock from the CLKIN pin or the output clock of

the 32.768-KHz real-time clock (RTC) oscillator. The selection of the input reference clock is based on the

state of the CLK_SEL pin. The CLK_SEL pins is required to be statically tied high or low and cannot

change dynamically after reset.

In addition, the DSP requires a reference clock for USB applications. The USB reference clock is

generated using a dedicated on-chip oscillator with a 12-MHz external crystal connected to the USB_MXI

and USB_MXO pins.

The USB reference clock is not required if the USB peripheral is not being used. To completely disable the

USB oscillator, connect the USB_MXI pin to ground (VSS) and leave the USB_MXO pin unconnected. The

USB oscillator power pins (USB_VDDOSC and USB_VSSOSC) should also be connected to ground.

The RTC oscillator generates a clock when a 32.768-KHz crystal is connected to the RTC_XI and

RTC_XO pins. The 32.768-KHz crystal can be disabled if CLKIN is used as the clock source for the DSP.

However, when the RTC oscillator is disabled, the RTC peripheral will not operate and the RTC registers

(I/O address range 1900h – 197Fh) will not be accessible. This includes the RTC power management

connect the RTC_XI pin to CVDDRTC and the RTC_XO pin to ground.

For more information on crystal specifications for the RTC oscillator and the USB oscillator, see

Section 6.4, External Clock Input From RTC_XI, CLKIN, and USB_MXI Pins.

Device Configuration

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