TPIC84125-Q1 Datasheet, PDF (17/29 Pages) Texas Instruments – LOW-FREQUENCY ANTENNA DRIVER FOR PASSIVE START AND PASSIVE ENTRY

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APPLICATION OVERVIEW
Typical Application Circuit
C1
0.1uF, 0805, 100V, 10%, X7R, ESR<50mOhm
GND
2
1
5V
GND
62k, 0805, 1/10W, .5%, 25ppm
GND
R1
5V
CLK_IN
SDO
SDI
SCLK
NCS
U1
1
VS2_decoup
2
AT1
3
4
AT2
5
Test
VA
6
Rbias
7
AGND
8
9
DGND
VD
10
CLK_IN
11
SDO
12
13
SDI
SCLK
14
NCS
TPIC84134-Q1
SLDS176 – AUGUST 2010
Vs
R2
28
VS
Out1
27
Out1
26 Out2
Out2
25
PGND
24 Out3
Out3
Out4
23
Out4
VS
22
21
VS
20
Out5
Out5
Out6
19
Out6
PGND
18
17 Out7
Out7
16
Out8
Out8
VS
15
R3
Vs
R4
Vs
L_ant
C_ant
L_ant
C_ant
GND
GND
GND
NOTE: Analog ground, digital ground, power ground, as well as the power pad must be connected together with a low
impedance path.
Figure 8. Typical Application Circuit
Necessary External Components
V_S/2: Pin 1 requires a 100nF capacitor with at least 10% tolerance or better, and ESR (equivalent series
resistance) of less than 50mΩ.
R_BIAS: Pin 6 requires a 62kΩ, 1% or better tolerance, 50ppm or better temperature coefficient.
Output Channels
The output channels require current limiting resistors to insure the source/sink current of the outputs does not
exceed the minimum AC current detection threshold of 0.9 A. Besides current limiting, these resistors affect the
Q-factor of the antenna. The output channels require 3V headroom at each rail to avoid clipping. Therefore, for
an output signal of 24 Vpp, V_S must be at least 30V.
Copyright © 2010, Texas Instruments Incorporated
Product Folder Link(s): TPIC84134-Q1
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