TMD2672

DIGITAL PROXIMITY DETECTOR

TAOS149C − AUGUST 2012

12

r

r

Copyright

E 2012, TAOS Inc.

The LUMENOLOGY

r Company

www.taosinc.com

State Diagram

The system state machine shown in Figure 6 provides an overview of the states and state transitions that

provide system control of the device. This section highlights the programmable features that affect the state

machine cycle time, and provides details to determine system level timing.

When the proximity detection feature is enabled (PEN), the state machine transitions through the Prox Init, Prox

Accum, Prox Wait, and Prox ADC states. The Prox Init and Prox Wait times are a fixed 2.73 ms, whereas the

Prox Accum time is determined by the number of proximity LED pulses (PPULSE) and the Prox ADC time is

determined by the integration time (PTIME). The formulas to determine the Prox Accum and Prox ADC times

are given in the associated boxes in Figure 10. If an interrupt is generated as a result of the proximity cycle, it

will be asserted at the end of the Prox ADC state and transition to the Sleep state if SAI is enabled.

When the power management feature is enabled (WEN), the state machine will transition in turn to the Wait

state. The wait time is determined by WLONG, which extends normal operation by 12

WTIME. The formula to determine the wait time is given in the box associated with the Wait state in Figure 10.

Prox

Wait

Sleep

Idle

Wait

Prox

Init

Prox

Accum

Prox

ADC

Prox

Time: 2.73 ms

PPULSE: 0 ~ 255 pulses

Time: 16.0

μs/pulse

Range: 0 ~ 4.1 ms

Time: 2.73 ms

PTIME: 1 ~ 256 steps

Time: 2.73 ms/step

Range: 2.73 ms ~ 699 ms

WTIME: 1 ~ 256 steps

WLONG = 0

WLONG = 1

Time:

2.73 ms/step

32.8 ms/step

Range:

2.73 ms ~ 699 ms

32.8 ms ~ 8.39s

!WEN

!PON

WEN

!PEN & WEN

Note: PON, PEN, WEN, and SAI are fields in the Enable register (0x00).

PEN

INT & SAI

Figure 10. Expanded State Diagram