TMD26721 datasheet(14/29 Pages) AMSCO

14 / 29 page

TMD2672

DIGITAL PROXIMITY DETECTOR

TAOS149C − AUGUST 2012

The LUMENOLOGY

r Company

E 2012, TAOS Inc.

www.taosinc.com

Power Management

Power consumption can be managed with the Wait state because the wait state consumes only 90

μA of IDD

current. An example of the power management feature is shown in Table 1. With the assumptions provided in

the example, the average IDD is estimated to be 157 μA.

Table 1. Power Management

SYSTEM STATE MACHINE

STATE

PROGRAMMABLE

PARAMETER

PROGRAMMED VALUE

DURATION

TYPICAL

CURRENT

Prox Init

2.73 ms

0.195 mA

Prox Accum

PPULSE

0x04

0.064 ms

Prox Accum − LED On

0.029 ms (Note 1)

103 mA

Prox Accum − LED OFF

0.035 ms (Note 2)

0.195 mA

Prox Wait

2.73 ms

0.195 mA

Prox ADC

PTIME

0xFF

2.73 ms

0.195 mA

Wait

WTIME

0xEE

49 2 ms

0 090 mA

Wait

WLONG

49.2 ms

0.090 mA

NOTES: 1. Prox Accum − LED On time = 7.3

μs per pulse

× 4 pulses = 29.3μs = 0.029 ms

2. Prox Accum − LED Off time = 8.7

μs per pulse

× 4 pulses = 34.7μs = 0.035 ms

Average IDD Current = ((2.73 × 0.195) + (0.029 × 103) + (0.035 x 0.195) + (2 x 2.73 x0.195) + (49.2 × 0.090)) / 57.45 157 μA

Keeping with the same programmed values as the example, Table 2 shows how the average IDD current is

affected by the Wait state time, which is determined by WEN, WTIME, and WLONG. Note that the worst-case

current occurs when the Wait state is not enabled.

Table 2. Average IDD Current

WEN

WTIME

WLONG

WAIT STATE

AVERAGE IDD CURRENT

n/a

0 ms

556

μA

0xFF

2.73 ms

440

μA

0xEE

49.2 ms

157

μA

0x00

699 ms

μA

0x00

8389 ms

μA

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