LMX2492-Q1_15 Datasheet, PDF (30/42 Pages) Texas Instruments – LMX2492/LMX2492-Q1 14 GHz Low Noise Fractional N PLL with Ramp/Chirp Generation

LMX2492, LMX2492-Q1
SNAS624B – MARCH 2014 – REVISED MAY 2015
www.ti.com
9.2.4 Application Performance Plot - Flat Top Triangle Waveform
Now consider pattern as shown below. The ramp is sometimes used because it can better account for Doppler
Shift. The purpose for making the top and bottom portions flat is to help reduce the impact of the PLL
overshooting and undershooting in order to make the sloped ramped portions more linear.
Parameter
Ramp Duration
Range
Symbol
ΔT0
ΔT1
ΔT2
ΔT3
ΔF0
ΔF1
ΔF2
ΔF3
Value
10 uS
90 uS
10 uS
90 uS
0
400 MHz
0
-400 MHz
RAMP
RAMP0
RAMP1
RAMP2
RAMP3
RAMP0
tRAMP1t
RAMP2
RAMP0
tRAMP1t
RAMP2
RAMPx_LEN
10 us/ 100 MHz
=1000
90 us / 100 MHz
=9000
10 us/ 100 MHz
=1000
90 us / 100 MHz
=9000
RAMPx_INC
RAMPx_NEXT
0
1
(ΔF / Fpd) /RAMP1_LEN × 2²⁴
= (400/100)/9000 ×16777216 =
2
7457
0
3
(ΔF / Fpd) /RAMP1_LEN × 2²⁴
= (-400/100)/9000 ×16777216 =
-7457
Program in 2's complement of -
0
7457
= 2³⁰-7457 = 1073734367
RAMPx_RST
1
0
0
0
30
Submit Documentation Feedback
Copyright © 2014–2015, Texas Instruments Incorporated
Product Folder Links: LMX2492 LMX2492-Q1