ams Datasheet

Page 19

[v1-00] 2015-Mar-23

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TMD2672 − Principles of Operation

Power Management

Power consumption can be managed with the Wait state

because the wait state consumes only 90μA of IDD current. An

example of the power management feature is shown in

Figure 23. With the assumptions provided in the example, the

average IDD is estimated to be 157μA.

Figure 23:

Power Management

Note(s) and/or Footnote(s):

1. Prox Accum - LED On time = 7.3μs per pulse × 4 pulses = 29.3μs = 0.029ms

2. Prox Accum - LED Off time = 8.7μs per pulse × 4 pulses = 34.7μs = 0.035ms

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,

Figure 24 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 24:

Average IDD Current

System State

Machine State

Programmable

Parameter

Programmed

Value

Duration

Typical

Current

Prox Init

2.73ms

0.195mA

Prox Accum

PPULSE

0x04

0.064ms

Prox Accum − LED On

0.029ms (1)

103mA

Prox Accum − LED Off

0.035ms (2)

0.195mA

Prox Wait

2.73ms

0.195mA

Prox ADC

PTIME

0xFF

2.73ms

0.195mA

Wait

WTIME

0xEE

49.2ms

0.090mA

WLONG

0

WEN

WTIME

WLONG

Wait State

Average IDD Current

0n/a

n/a

0ms

556μA

1

0xFF

0

2.73ms

440μA

1

0xEE

0

49.2ms

157μA

1

0x00

0

699ms

99μA

10x001

8389ms

90μA