Datasheet

50uA
0 mA to 200 mA
(See the LEDRANGE bits
in the LEDCNTRL register.)
LED_ON
1 PA
TX_CTRL_SUP
LED_DRV_SUP
Device
Tx LED
Bridge
LED
Current
Control
DAC
Tx Reference
and Control
AFE4490
www.ti.com SBAS602F –DECEMBER 2012–REVISED OCTOBER 2013
Transmitter Power Path
The block diagram in Figure 73 shows the AFE4490 Tx subsystem power routing.
Figure 73. Transmit Subsystem Power Routing
LED Power Reduction During Periods of Inactivity
The diagram in Figure 74 shows how LED bias current passes 50 µA whenever LED_ON occurs. In order to
minimize power consumption in periods of inactivity, the LED_ON control must be turned off. Furthermore, the
TIMEREN bit in the CONTROL1 register should be disabled by setting the value to '0'.
Note that depending on the LEDs used, the LED may sometimes appear dimly lit even when the LED current is
set to 0 mA. This appearance is because of the switching leakage currents (as shown in Figure 74) inherent to
the timer function. The dimmed appearance does not effect the ambient light level measurement because during
the ambient cycle, LED_ON is turned off for the duration of the ambient measurement.
Figure 74. LED Bias Current
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