LTP5901-IPR datasheet(23/34 Pages) LINER

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LTP5901-IPR/LTP5902-IPR

59012iprfa

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operaTion

POWER SUPPLY

Eterna is powered from a single pin, VSUPPLY, which

powers the I/O cells and is also used to generate internal

supplies.Eterna’stwoon-chipDC/DCconvertersminimize

Eterna’s energy consumption while the device is awake. To

conserve power the DC/DC converters are disabled when

the device is in low power state. Eterna’s integrated power

supply conditioning architecture, including the two inte-

grated DC/DC converters and three integrated low dropout

regulators, provides excellent rejection of supply noise.

Eterna’s operating supply voltage range is high enough

to support direct connection to lithium-thionyl chloride,

Li-SOCl2, sources and wide enough to support battery

operation over a broad temperature range.

SUPPLY MONITORING AND RESET

Eterna integrates a power-on reset (PoR) circuit. As the

RESETn input pin is nominally configured with an internal

pull-up resistor, no connection is required. For a graceful

shutdown, the software and the networking layers should

be cleanly halted via API commands prior to assertion of

theRESETnpin.SeetheSmartMeshIPManagerAPIGuide

for details on the disconnect and reset commands. Eterna

includes a soft brown-out monitor that fully protects the

flash from corruption in the event that power is removed

while writing to flash. Integrated flash supervisory func-

tionality, in conjunction with a fault tolerant file system,

yields a robust non-volatile storage solution.

PRECISION TIMING

A major feature of Eterna over competing 802.15.4 prod-

uct offerings is its low power dedicated timing hardware

and timing algorithms. This functionality provides timing

precision two to three orders of magnitude better than

any other low power solution available at the time of

publication. Improved timing accuracy allows motes to

minimize the amount of radio listening time required to

ensure packet reception thereby lowering even further

the power consumed by SmartMesh networks. Eterna’s

patented timing hardware and timing algorithms provide

superior performance over rapid temperature changes,

further differentiating Eterna’s reliability when compared

with other wireless products. In addition, precise timing

enables networks to reduce spectral dead time, increasing

total network throughput.

APPLICATION TIME SYNCHRONIzATION

In addition to coordinating time slots across the network,

which is transparent to the user, Eterna’s timing manage-

mentisusedtosupporttwomechanismstosharenetwork

time. Having an accurate, shared, network-wide time base

enables events to be accurately time stamped or tasks to

be performed in a synchronized fashion across a network.

Eterna will send a time packet through its serial interface

when one of the following occurs:

• Eterna receives an API request to read time

• The TIMEn signal is asserted

TheuseofTIMEnhastheadvantageofbeingmoreaccurate.

The value of the timestamp is captured in hardware relative

to the rising edge of TIMEn. If an API request is used, due

to packet processing, the value of the timestamp may be

capturedseveralmillisecondsafterreceiptofthepacketdue

topacketprocessing.SeesectionTIMEnACCharacteristics,

for the time function’s definition and specifications.

TIME REFERENCES

Eterna includes three clock sources: an internal relaxation

oscillator, a low power oscillator designed for a 32.768kHz

crystal, and the radio reference oscillator designed for a

20MHz crystal.

Relaxation Oscillator

The relaxation oscillator is the primary clock source for

Eterna, providing the clock for the CPU, memory subsys-

tems, and all peripherals. The internal relaxation oscillator

is dynamically calibrated to 7.3728MHz. The internal re-

laxation oscillator typically starts up in a few μs, providing

an expedient, low energy method for duty cycling between

active and low power states. Quick start-up from the doze

state,definedintheStateDiagramsection,allowsEternato

wake up and receive data over the UART and SPI interfaces

by simply detecting activity on the appropriate signals.

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