PLL
HSPLLCTL.
PLLM[5..0]
USSXTIN
HSPLLCTL.
PLL_LOCK
½
PLL_CLK
(68 to 80 MHz)
USSXTOUT
OSC
HSPLLUSSXTLCTL.
OSCEN
HSPLLUSSXTLCTL.
OSCSTATE
USSXT_BOUT
HSPLLUSSXTLCTL.
XTOUTOFF
...SSXTLCTL.
OSCTYPE
HSPLLCTL.
PLLINFREQ
CH1_IN
PVSS
PVSS
PVCC
CH0_IN
CH0_OUT
CH1_OUT
PHY
PPG or
PPG_A
ASQ
UUPS
PGA
SD 12 or 14
MOD
Filter
Bias Generator
on SAPH_A only
GPIO
(software controlled)
Optional
external
signal
handling
Vout
OSC
PLL
USSXTIN USSXTOUT
USSXT_BOUT
USSXT
HSPLL
SAPH or SAPH_A
SDHS
DTC
RAM
(shared with LEA)
USS or USS_A module
PLL_CLK
Px.y
XPB0
XPB1
Introduction
479
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
High-Speed PLL (HSPLL)
20.1 Introduction
The High-Speed PLL (HSPLL) is one of the submodules in the Ultrasonic Sensing Solution (USS) module.
The USS module is designed for analog-to-digital converter (ADC) based ultrasonic sensing technology in
various measurement applications.
shows the block diagram of the USS module.
Figure 20-1. USS or USS_A Block Diagram
The HSPLL module is the dedicated clock generation module for the USS module. To measure the flow
speed using ultrasonic technology, the USS module requires a very low-jitter clock to achieve very high
accuracy between upstream and downstream measurements. The HSPLL consists of two blocks, OSC
and PLL. The output clock of the PLL is in the range of 68 MHz to 80 MHz.
shows the HSPLL
block diagram.
•
OSC (oscillator) block: Generates a clock of 4 MHz or 8 MHz from USSXT (crystal or ceramic
resonator).
•
PLL (phase-locked loop): Generates a clock in the range of 68 MHz to 80 MHz from the output of the
OSC.
Figure 20-2. HSPLL Block Diagram