AN11524
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© NXP Semiconductors N.V. 2015. All rights reserved.
Application note
Rev. 1 — 17 February 2015
31 of 54
NXP Semiconductors
AN11524
NXQ1TXA6 Evaluation Board
When the ASEL1, ASEL2 and ASEL3 lines are not driven the OPT2 input expects a stable
2.495 reference voltage present at its input. The shunt regulator U102 TL431BFDT, with
an accuracy of 0.5 %, is used.
The power stage DC voltage is measured in input of VSNS using R115 and R116.
Use only 1 % tolerance resistors in Configuration (OPT0 and OPT1) and Voltage Sensing
(VSNS) circuits.
7.5 Thermal protection
NTC201 provides temperature sensing which allows the controller (option) to sense the
temperature for safety purposes. When using a thermistor of type b57551G1103F005, the
transmitter stops power transfer at temperatures of 70
C and higher. When the
temperature measured by the NTC is below 60
C, the transmitter commences power
transfer. If not used, the NTC input must be connected to VDD.
Fig 17. Configuration and voltage measurement
aaa-015897
IS-
[2,3,4]
INPUT VOLTAGE
MEASUREMENT
VOLTAGE
REFERENCE
SETTINGS CONFIGURATION
LP_VSUP
VSNS
R103
R104
R106
R113
R114
R105
R116
R115
OPT1
ASEL3
ASEL2
ASEL1
OPT2
R119
U102
C106
C105