BQ500412 Datasheet, PDF (12/28 Pages) Texas Instruments – Low System Cost, Wireless Power Controller for WPC TX A6

bq500412
SLUSBO2A – NOVEMBER 2013 – REVISED DECEMBER 2013
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Option Select Pins
Several pins on the bq500412 are allocated to programming the FOD and PMOD Loss Threshold and the LED
mode of the device. At power up, a bias current is applied to pins LED_MODE and LOSS_THR and the resulting
voltage measured in order to identify the value of the attached programming resistor. FOD, PMOD and
FOD_CAL pin values are enabled and read sequentially from the same LOSS_THR bias current. The values of
the operating parameters set by these pins are determined using Table 2. For LED_MODE, the selected bin
determines the LED behavior based on Table 1; for the LOSS_THR, the selected bin sets a threshold used for
parasitic metal object detection (see Parasitic Metal Detection (PMOD) and Foreign Object Detection (FOD)
section). Table 1.
bq500412
Resistors
to set
options
LED_MODE
44
LOSS_THR
43
To 12-bit ADC
FOD
13
PMOD FOD_CAL
6
22
Figure 3. Option Select Pin Programming
LED Indication Modes
The bq500412 can directly drive up to three (3) LED outputs (pin 7, pin 8 and pin 25) through a simple current
limit resistor (typically 470 Ω), based on the mode selected. The current limit resistors can be individually
adjusted to tune or match the brightness of the LEDs. Do not exceed the maximum output current rating of the
device. The resistor in Figure 3 connected to pin 44 and GND selects the desired LED indication scheme in
Table 1.
• LED modes permit the use of one to three indicator LED's. Amber in the 2-LED mode is obtained by turning
on both the green and red.
• LEDs can be turned on solid or configured to blink either slow (approx. 1.6s period) or fast (approx. 400ms
period).
• Except in modes 2 and 9, the charge complete state is only maintained for 5 seconds after which it reverts to
idle. This permits the processor to sleep in order to reduce standby power consumption. In other modes,
external logic, such as a flip-flop, may be implemented to maintain the charge complete indication if desired.
• LED modes 5 and 8 will display a sequence of red-amber-green, for 0.5 seconds when the device is first
powered up.
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