0

VS /2

VS

0

VS /2

VS

Out1

Out2

2 Bytes

Counter for start of

transmission with Gain 2:

16 bits

Counter for transmission

in Gain 2:

Transmitted

Data (Bits)

4 bits

Length of

destroy bits :

8 bits

Counter for start

of destroy bits

:

Start

8

16

32

56

( V )

TPIC84134-Q1

www.ti.com

SLDS176 – AUGUST 2010

Gains

Gain1 is a programmable gain for the output antenna working in normal mode to control the transmission power.

Gain2 allows the user to change the gain of the transmitted telegram for a programmable number of data bits

after which the telegram is continued in gain1. The time at which gain2 begins is programmable in the CSR;

alternatively, if the length of bits sent in gain2 is zero (0) the entire telegram is transmitted in gain1. Note, these

gains are not cascaded; it is either Gain1 or Gain2.

Gain for destroy bit transmission dictates the gain for the output channels set to "destroy bits". The gain for

destroy bits is a logarithmic scale and it is set to 500 mVpp by default.

Figure 3 shows an example in which Out1 is configured to transmit the telegram, using both Gain1 and Gain2.

The counter for start of transmission with Gain2 = 2 Bytes, and the counter for transmission in gain2 = 16 bits.

Note that the transmission resumes at Gain1 after the transmission at Gain2. The diagram also displays Out2

with destroy bits where counter for start of destroy bits = 8 bits, and Length of destroy = 4 bits.

Figure 3. Transmitted Telegram Sample Gain1 And Gain2

Multiplexer (Mux)

A multiplexer is used to pick between the various gains of the signal to each output, as well as selecting the

phase ( 0° or 180°) of the transmitting antennas.

A maximum of two outputs, or 2 half-bridges, can be activated at the same time in normal mode, where each is

designed to drive the required power into the antenna. Further, all other outputs can also be activated with

destroy bits at the same time(at a lower Vpp). As the bridges operate in a linear mode, the sine wave generation

at the bridge output is optimized to reduce EMI emissions and power dissipation.

Copyright © 2010, Texas Instruments Incorporated

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