Datasheet

bq500210
SLUSAL8C –JUNE 2011–REVISED SEPTEMBER 2012 www.ti.com
Thermal Protection
The bq500210 can provide thermal protection to the transmitter. An external NTC resistor can be placed in the
most thermally challenged area, which usually is the center of the transmitting coil, and connected between the
dedicated pin 2 and GND. The threshold on pin 2 is set to 1.00V. The NTC resistor and the resistor from pin 2 to
V
CC
create a temperature sensitive divider. The user has full flexibility choosing the NTC resistor and the value of
the resistor from pin 2 to V
CC
to set the desired temperature when the system shuts down.
R
TEMP_IN
= 2.3 x R
NTC
(T
MAX
) (1)
The system will attempt to restore normal operation after approximately five minutes of being in the suspended
mode due to tripping the over-temperature threshold, or if the receiver is removed. The bq500210 has a built-in
thermal sensor that prevents the die temperature from exceeding 135°C. This sensor has ~10°C hysteresis.
Audible Notification on Power Transfer Begin
The bq500210 is capable of activating two types of buzzers to indicate that power transfer has begun. Pin 24
outputs a high logic signal for 0.4s that is suitable to activate DC type buzzers with built in tone generators, or
other types of sound generators, or custom indication systems. Pin 23 outputs for 0.4 seconds a 4 kHz square
wave signal suitable for inexpensive AC type ceramic buzzers.
Power-On Reset
The bq500210 has an integrated power-on reset (POR) circuit that monitors the supply voltage. At power-up, the
POR circuit detects the V33D rise. When V33D is greater than V
RESET
, the device initiates an internal startup
sequence. At the end of the startup sequence, the device begins normal operation.
External Reset
The device 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. To avoid an erroneous trigger caused by noise, a 10kΩ pull up
resistor connected to 3.3V is recommended.
Parasitic Metal Object Detection (PMOD)
As a safety feature, the bq500210 can be configured to detect the presence of a parasitic metal object placed in
the vicinity of the magnetic field. The bq500100 uses the Rectified Power Packet information and the measured
transmitter input-power to calculate parasitic losses in the system. When an excessive power loss is detected,
the device will blink the red LED to warn about this undesirable condition. If during a twenty second warning time
the parasitic metal object is not removed, the controller will disable power transfer. After being in halt for five
minutes, the bq500210 will attempt normal operation. If the object that caused excessive power dissipation is still
present, the sequence will be repeated over and over again. If the metal object is removed during this twenty
second warning time, then normal operation will be restored promptly.
To facilitate the parasitic loss function, the bq500210 monitors the input voltage and the input current supplied to
the power drive circuit.
The PMOD_THR pin is used to set the threshold at which the PMOD is activated. The highest bin, the pin is left
floating, disables the PMOD feature.
Note: The WPC Specification V1.0 does not define the requirements and thresholds for the PMOD feature.
Hence, metal object detection may perform differently with different products. Therefore, the threshold setting is
determined by the user. In most desktop wireless charger applications, a PMOD threshold setting of 0.8W has
shown to provide acceptable results in stopping power transfer and preventing small metal objects like coins,
pharmaceutical wraps, etc. from becoming dangerously hot when placed in the path of the wireless power
transfer. Figure 2 depicts PMOD performance measured on a bq500210 EVM with a bq51013 EVM. The
parasitic metal loss is emulated by loading the output of the rectifier in the bq51013 EVM.
ADVANCED CHARGE INDICATION SCHEMES
The WPC specification provides an End of Power Transfer message (EPT–01) to indicate charge complete.
Upon receipt of the charge complete message, the bq500210 will change the LED indication as defined by the
LED_MODE pin (normally solid green LED output), and halt power transfer for 5 minutes.
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