TMD27721 Datasheet, PDF (16/35 Pages) TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS – DIGITAL ALS and PROXIMITY MODULE

TMD2772
DIGITAL ALS
and PROXIMITY MODULE
TAOS147E − DECEMBER 2012
Power Management
Power consumption can be managed with the Wait state, because the Wait state typically consumes only 90 μA
of I_DD current. An example of the power management feature is given below. With the assumptions provided
in the example, average I_DD is estimated to be 176 μA.
Table 1. Power Management
SYSTEM STATE MACHINE PROGRAMMABLE
STATE
PARAMETER
PROGRAMMED VALUE
DURATION
Prox Init
2.73 ms
lid ^{Prox Accum}
PPULSE
0x04
0.064 ms
Prox Accum − LED On
0.029 ms (Note 1)
Prox Accum − LED OFF
0.035 ms (Note 2)
a Prox Wait
2.73 ms
Prox ADC
PTIME
0xFF
2.73 ms
ill ^{v Wait}
WTIME
WLONG
0xEE
0
49.2 ms
ALS Init
2.73 ms
ALS ADC
ATIME
0xEE
t 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
49.2 ms
TYPICAL
CURRENT
0.195 mA
103 mA
0.195 mA
0.195 mA
0.195 mA
0.090 mA
0.195 mA
0195 mA
G _{s Average IDD Current = ((0.029 × 103) + (0.035 x 0.195) + (2.73 × 0.195) +}
A ^t _{(49.2 × 0.090) + (49.2 × 0.195) + (2.73 × 0.195 × 3)) / 109  176 μA}
s ⁿ _{Keeping with the same programmed values as the example, Table 2 shows how the average IDD current is}
e _{affected by the Wait state time, which is determined by WEN, WTIME, and WLONG. Note that the worst-case}
m ^{t current occurs when the Wait state is not enabled.}
a ⁿ _WEN
o ₀
c ₁
1
l ₁
Technica ¹
WTIME
n/a
0xFF
0xEE
0x00
0x00
Table 2. Average I_DD Current
WLONG
n/a
0
0
0
1
WAIT STATE
0 ms
2.73 ms
49.2 ms
699 ms
8389 ms
AVERAGE I_DD CURRENT
245 μA
238 μA
175 μA
102 μA
91 μA
The LUMENOLOGY r Company
r
r
www.taosinc.com
Copyright E 2012, TAOS Inc.
15