ESICH0
ESICH1
ESICH2
00
01
10
11
ESICH3
1
0
ESICA2EN
ESICA2X
2
00
01
10
11
DAC 12 Bit
ESIDAC2R0
ESIDAC2R1
ESIDAC2R2
ESIDAC2R3
ESIDAC2R4
ESIDAC2R5
ESIDAC2R6
ESIDAC2R7
ESIDAC(tsm)
ESIDAC2EN
ESICI0
ESICI1
ESICI2
ESICI3
AFE1
Excitation
Logic
+
ESICA(tsm)
-
ESIC2OUT
ESICA2INV
+
1
0
-
DAC2
ESITEST3
ESITEST2
ESICHx(tsm)
ESIC2OUT
Selected input channel is 00b.
Selected input channel is 01b
Selected input channel is 10b
Selected input channel is 11b
Hysteresis programmable with the two registers.
Hysteresis programmable with the two registers.
Hysteresis programmable with the two registers.
Hysteresis programmable with the two registers.
.
.
.
8 MSB
4 LSB
en
+
en
ESI Operation
969
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
Extended Scan Interface (ESI)
Figure 37-3. ESI Analog Front End AFE2 Block Diagram
37.2.1.1 Excitation
The excitation circuitry is used to excite the LC sensors or to power the resistor dividers. The excitation
circuitry is shown in
for one LC sensor connected. When the ESITEN bit is set and the ESISH
bit is cleared, the excitation circuitry is enabled and the sample-and-hold circuitry is disabled.
When the ESIEX(tsm) signal from the timing state machine is high, the ESICHx input of the selected
channel is connected to ground (ESIDVSS pin) and the ESICOM input is connected to the mid-voltage
generator to excite the sensor. The ESILCEN(tsm) signal must be high for excitation. While one channel is
excited and measured, all other channels are automatically disabled. Only the selected channel is excited
and measured.
The excitation period should be long enough to overload the LC sensor slightly. After excitation the
ESICHx input is released from ground when ESIEX(tsm) = 0, and the LC sensor can oscillate freely. The
oscillations swing above the positive supply but are clipped by the protection diode to the positive supply
voltage plus one diode drop. This gives consistent maximum oscillation amplitude.
At the end of the measurement, the sensor should be damped by setting ESILCEN(tsm) = 0 to remove
any residual energy before the next measurement.