TMD27721 datasheet(16/35 Pages) TAOS

16 / 35 page

TMD2772

DIGITAL ALS

and PROXIMITY MODULE

TAOS147

E − DECEMBER 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 typically consumes only 90

μA

of IDD current. An example of the power management feature is given below. With the assumptions provided

in the example, average IDD is estimated to be 176 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

ALS Init

2.73 ms

0.195 mA

ALS ADC

ATIME

0xEE

49.2 ms

0195 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 = ((0.029

× 103) + (0.035 x 0.195) + (2.73 × 0.195) +

(49.2

× 0.090) + (49.2 × 0.195) + (2.73 × 0.195 × 3)) / 109 176 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

245

μA

0xFF

2.73 ms

238

μA

0xEE

49.2 ms

175

μA

0x00

699 ms

102

μA

0x00

8389 ms

μA

TMD27721 Datasheet(PDF) 16 Page - TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS

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