TSL27721 datasheet(25/56 Pages) AMSCO

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[v1-00] 2016-Aug-26

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TSL2772 − Principles Of Operation

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 182 μA.

Figure 27:

Power Management

Note(s):

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 × 119) + (0.035 × 0.200) + (2.73 ×

0.200) + (49.2

× 0.090) + (49.2 × 0.200) + (2.73 × 0.200 × 3)) /109

≈ 182

μA

Keeping with the same programmed values as the example,

Figure 28 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.

System State

Machine State

Programmable

Parameter

Programmed

Value

Duration

Typical

Current

Prox Init

2.73 ms

0.200 mA

Prox Accum

PPULSE

0x04

0.064 ms

Prox Accum − LED ON

0.029 ms (1)

119 mA

Prox Accum − LED OFF

0.035 ms(2)

0.200 mA

Prox Wait

2.73 ms

0.200 mA

Prox ADC

PTIME

0xFF

2.73 ms

0.200 mA

Wait

WTIME

0xEE

49.2 ms

0.090 mA

WLONG

ALS Init

2.73 ms

0.200 mA

ALS ADC

ATIME

0xEE

49.2 ms

0.200 mA

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