Datasheet

COMM1 COMM2
RECTIFIER
24W 24W
COMM_DRIVE
Preamble Header Message Checksum
bq51013B
SLUSB62A –MARCH 2013–REVISED OCTOBER 2013 www.ti.com
Each packet format is organized as shown in Figure 34.
Figure 34. Packet Format (WPC volume 1: Low Power, Part 1 Interface Definition)
Figure 25 above shows an example waveform of the receiver sending a rectified power packet (header 0x04).
Communication Modulator
The bq5101xB provides two identical, integrated communication FETs which are connected to the pins COM1
and COM2. These FETs are used for modulating the secondary load current which allows bq5101xB to
communicate error control and configuration information to the transmitter. Figure 35 below shows how the
COMM pins can be used for resistive load modulation. Each COMM pin can handle at most a 24Ω
communication resistor. Therefore, if a COMM resistor between 12Ω and 24Ω is required COM1 and COM2 pins
must be connected in parallel. bq5101xB does not support a COMM resistor less than 12Ω.
Figure 35. Resistive Load Modulation
In addition to resistive load modulation, the bq5101xB is also capable of capacitive load modulation as shown in
Figure 36 below. In this case, a capacitor is connected from COM1 to AC1 and from COM2 to AC2. When the
COMM switches are closed there is effectively a 22 nF capacitor connected between AC1 and AC2. Connecting
a capacitor in between AC1 and AC2 modulates the impedance seen by the coil, which will be reflected in the
primary as a change in current.
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