ams Datasheet

Page 23

[v1-01] 2018-Mar-14

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TCS3772 − Principles of Operation

Power Management

Power consumption can be managed with the Wait state,

because the Wait state typically consumes only 65

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 186 μA.

Figure 28:

Power Management

Note(s):

1. Prox Accum - LED ON time = 6.3

μs per pulse × 4 pulses = 25.2 μs = 0.025 ms

2. Prox Accum - LED OFF time = 7.7

μs per pulse × 4 pulses = 30.9 μs = 0.031 ms

Average IDD Current = ((0.025 × 109) + (0.031 × 0.235) + (2.40 × 0.235) + (43.1 × 0.065) + (43.1 × 0.263) + (2.40 × 0.235 × 2)) / 93 ≈ 186 μA

Keeping with the same programmed values as the example,

Figure 29 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.

Figure 29:

Average IDD Current

System State

Machine State

Programmable

Parameter

Programmed

Value

Duration

Typical

Current

Prox Accum

PPULSE

0x04

0.056 ms

Prox Accum - LED ON

0.025 ms (1)

109 mA

Prox Accum - LED OFF

0.031 ms (2)

0.235 mA

Prox Wait

2.40 ms

0.235 mA

Prox ADC

PTIME

0xFF

2.40 ms

0.235 mA

Wait

WTIME

0xEE

43.1 ms

0.065 mA

WLONG

0

ALS Init

2.40 ms

0.235 mA

ALS ADC

ATIME

0xEE

43.1 ms

0.235 mA

WEN

WTIME

WLONG

WAIT State

Average IDD Current

0

n/a

n/a

0 ms

289

μA

1

0xFF

0

2.40 ms

279

μA

1

0xEE

0

43.1 ms

186

μA

1

0x00

0

613 ms

82

μA

10x00

1

7.36 s

67

μA