BQ500414Q Datasheet, PDF (16/34 Pages) Texas Instruments – Qi Compliant Wireless Power Transmitter Manager

bq500414Q
SLUSBE4B – JANUARY 2014 – REVISED JUNE 2014
www.ti.com
8.3.11 Power Transfer Start Signal
The bq500414Q features two signal outputs to indicate that power transfer has begun. Pin 23 BUZ_AC outputs a
400-ms duration, 4-kHz square wave for driving low cost AC type ceramic buzzers. Pin 24 BUZ_DC outputs logic
high, also for 400-ms, which is suitable for DC type buzzers with built-in tone generators, or as a trigger for any
type of customized indication scheme. Do not exceed 4-mA loading from either of these pins which is more than
adequate for small signaling and actuation. If not used, these pins should be left open.
8.3.12 Power-On Reset
The bq500414Q has an integrated Power-On Reset (POR) circuit which monitors the supply voltage and handles
the correct device startup sequence. Additional supply voltage supervisor or reset circuits are not needed.
8.3.13 External Reset, RESET Pin
The bq500414Q can be forced into a reset state by an external circuit connected to the RESET pin. A logic low
voltage on this pin holds the device in reset. For normal operation, this pin is pulled up to 3.3-V supply with a 10-
kΩ pull-up resistor.
8.3.14 Trickle Charge and CS100
The WPC specification provides an End-of-Power Transfer message (EPT–01) to indicate charge complete.
Upon receipt of the charge complete message, the bq500414Q will change the LED indication. The exact
indication depends on the LED_MODE chosen.
In some battery charging applications there is a benefit to continue the charging process in trickle-charge mode
to top off the battery. There are several information packets in the WPC specification related to the levels of
battery charge (Charge Status). The bq500414Q uses these commands to enable top-off charging. The
bq500414Q changes the LED indication to reflect charge complete when a Charge Status message is 100%
received, but unlike the response to an EPT, it will not halt power transfer while the LED indicates charge
complete. The mobile device can use a CS100 packet to enable trickle charge mode.
If the reported charge status drops below 90%, normal charging indication will be resumed.
8.3.14.1 Over-Current Protection
The bq500414Q has an integrated current protection feature which monitors the input current reported by the
current sense resistor and amplifier. If the input current exceeds a predetermined threshold, a fault is indicated
and power transfer is halted for one minute.
If this feature is desired, the sense resistor and amplifier are required. If this feature is not desired, and WPC
v1.1 compliant (FOD) is not required, the I_SENSE input pin to the bq500414Q (pin 42) should be grounded.
NOTE
Always terminate the I_SENSE pin (pin 42), either with the output of a current monitor
circuit or by connecting to ground.
8.3.15 Over-Voltage Protection
When the Rx is quickly moved from a low coupling position to a high coupling position, the rectified voltage on
the Rx could get to very high before the Tx reacts to the change. Per WPC protocol, there is certain time duration
between the Control Error Packages, so the Tx will not be able to react instantaneously. The bq500414Q uses a
peak-detect circuit to prevent the Rx from being over-voltage.
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