Datasheet

bq500410A

www.ti.com

SLUSB96 – NOVEMBER 2012

Power Transfer Start Signal

The bq500410A features two signal outputs to indicate that power transfer has begun. Pin 23 outputs a 400-ms

duration, 4-kHz square wave for driving low cost AC type ceramic buzzers. Pin 24 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.

Power-On Reset

The bq500410A 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.

External Reset, RESET Pin

The bq500410A 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

with a 10-kΩ

pull-up resistor.

Trickle Charge and CS100

CS100 is supported. If CS100 is reported by the RX, the bq500410A indicates that charge is complete.

The WPC specification provides an End-of-Power Transfer message (EPT) to indicate charge complete. Upon

receipt of the charge complete message, the bq500410A changes the LED indication to solid green LED output

and halt power transfer for 5 seconds. Subsequently, transmitters pings the receiver again to see if its status has

changed, assuming it receives another EPT, the LED mode stays the same.

The WPC specification also provides reporting of the level of battery charge (Charge Status). In some battery

charging applications there is a benefit to continue the charging process in trickle-charge mode to top off the

battery. The bq500410A changes the LED indication to reflect charge complete when a 'Charge Status 100%'

message is received, but unlike the response to an EPT message, it does not halt power transfer while the LED

is solid green. The RX, the mobile device being charged, uses a CS100 packet to enable trickle charge mode.

Current Monitoring Requirements

The bq500410A is WPC1.1 ready. In order to enable the PMOD or FOD features, current monitoring must be

provided in the design.

Current monitoring is optional however, it is used for the foreign metal protection features and over current

protection. The system designer can choose not to include the current monitor and remain WPC1.0 compliant.

Alternately, the additional current monitoring circuitry can be added to the hardware design but not loaded. This

would enable a forward migration path to future WPC1.1 compatibility.

For proper scaling of the current monitor signal, the current sense resistor should be 20 mΩ and the current

shunt amplifier should have a gain of 50, such as the INA199A1. The current sense resistor has a temperature

stability of ±200 PPM. Proper current sensing techniques in the application hardware should also be observed.

Product Folder Links: bq500410A