NXP Semiconductors
UM11227
NTM88 family of tire pressure monitor sensors
UM11227 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2020. All rights reserved.
User manual Rev. 6 — 24 April 2020
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10.16.11.12 RFM Pre-charge control register (RFPRECHARGE)
Table 128. RFM Pre-charge control register (RFPRECHARGE) (address $1861)
Bit 7 6 5 4 3 2 1 0
R 0 0 AREGOK 0
W
TIMEOUT1 TIMEOUT0
— —
ENARE
GCOMP
AREGPC
— —
Reset ($40) 0 1 0 0 0 0 0 0
Table 129. RFPRECHARGE register field descriptions
Field Description
7:6
TIMEO
UT[1:0]
TIMEOUT[1:0] - RF timeout selection.
The timeout selection provides a period to allow the PLL to lock, including the Pre-charge if enabled. If the
timeout is reached and the PLL has not locked, the RF state machine will halt and set the error status flag
RFEF to 1. Times listed below are approximate based upon the crystal: NDK NX3225SA, 26.000 MHz.
When AREGPC = 0:
0 0 = disabled
0 1 = 800 µs; Result of Reset
1 0 = 1.6 ms
1 1 = 2.4 ms
When AREGPC = 1:
0 0 = disabled
0 1 = 1.304 ms; Result of Reset
1 0 = 2.104 ms
1 1 = 2.904 ms
3
ENARE
GCOMP
ENAREGCOMP – Pre-charge comparator.
To conserve power, the pre-charge comparator is transient-enabled, meaning that it turns on only when
required and is off otherwise. The ENAREGCOMP bit can be set to force the comparator on continuously.
During test, this functionality is used to test the comparator. In the application, the MCU can use this
function to check if the VREG pin is already pre-charged, i.e. the MCU can enable the comparator, read the
value of the AREGOK bit, then disable the comparator (to avoid wasting power).
0 = disabled; Result of Reset
1 = enabled
2
AREGPC
AREGPC – Pre-charge external analog regulator load capacitor function.
Enables automatic current-limited pre-charging of the RF analog regulator’s external capacitor before
transmitting. Use this function to avoid large inrush currents that can occur when the RF analog regulator is
enabled.
0 = disabled; Result of Reset
1 = enabled
1
AREGOK
AREGOK – Read-only Pre-charge completion status:
Read-only bit that returns the output of the pre-charge comparator. It is only meaningful when the
comparator is enabled, i.e. when ENAREGCOMP=1.
0 = pre-charge not complete; Result of Reset
1 = pre-charge completed.
10.17 Analog-to-Digital converter (ADC) module
The following is a brief description of the features the ADC module provides:
• Execute conversions with 8-, 10-, or 12-bit resolutions
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