LTC6948_15 Datasheet, PDF (1/36 Pages) Linear Technology – Ultralow Noise 0.37GHz to 6.39GHz Fractional-N Synthesizer with Integrated VCO

LTC6948
Features
Ultralow Noise 0.37GHz to
6.39GHz Fractional-N Synthesizer
with Integrated VCO
Description
n _{Low Noise Fractional-N PLL with Integrated VCO}
n _{No ∆-∑ Modulator Spurs}
n _{18-Bit Fractional Denominator}
n _{–226 dBc/Hz Normalized In-Band Phase Noise Floor}
n _{–274 dBc/Hz Normalized In-Band 1/f Noise}
n _{–157 dBc/Hz Wideband Output Phase Noise Floor}
n _{Excellent Integer Boundary Spurious Performance}
n _{Output Divider (1 to 6, 50% Duty Cycle)}
n _{Output Buffer Muting}
n _{Reference Input Frequency Up to 425MHz}
n _{Fast Frequency Switching}
n _{FracNWizard™ Software Design Tool Support}
Applications
n _{Wireless Basestations (LTE, WiMAX, W-CDMA, PCS)}
n _{Microwave Data Links}
n _{Military and Secure Radio}
n _{Test and Measurement}
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
FracNWizard is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
The LTC^®6948 is a high performance, low noise, 6.39GHz
phase-locked loop (PLL) with a fully integrated VCO,
including a reference divider, phase-frequency detector
(PFD), ultralow noise charge pump, fractional feedback
divider, and VCO output divider.
The fractional divider uses an advanced, 4th order Δ∑
modulator which provides exceptionally low spurious
levels. This allows wide loop bandwidths, producing ex-
tremely low integrated phase noise values.
The programmable VCO output divider, with a range of 1
through 6, extends the output frequency range.
Output Frequency Options
LTC6948-1 LTC6948-2 LTC6948-3 LTC6948-4
O_DIV = 1 2.240 to 3.740 3.080 to 4.910 3.840 to 5.790 4.200 to 6.390
O_DIV = 2 1.120 to 1.870 1.540 to 2.455 1.920 to 2.895 2.100 to 3.195
O_DIV = 3 0.747 to 1.247 1.027 to 1.637 1.280 to 1.930 1.400 to 2.130
O_DIV = 4 0.560 to 0.935 0.770 to 1.228 0.960 to 1.448 1.050 to 1.598
O_DIV = 5 0.448 to 0.748 0.616 to 0.982 0.768 to 1.158 0.840 to 1.278
O_DIV = 6 0.373 to 0.623 0.513 to 0.818 0.640 to 0.965 0.700 to 1.065
Typical Application
6.3GHz Wideband Receiver
1.6nF
76.8Ω 10µH
0.1µF ^3.3V
5V
15Ω
1µF _2.4nF
76.8Ω
0.1µF
UNUSED OUTPUT
AVAILABLE FOR
OTHER USE
50Ω
1µF
100MHz
51.1Ω
SPI BUS
3.3V
0.1µF
3.3V
3.3V
0.1µF
1µF
REF⁺
STAT
CS
SCLK
SDI
SDO
LDO
V_D+
0.01µF
LTC6948-4
BVCO
GND
CM_A
CM_B
CM_C
GND
TB
TUNE
56nF
0.01µF
1µF
2.2µF
68nH
68nH _100pF
3.3V
0.01µF
R = 2, f_PFD = 50MHz
N = 84 TO 127.8
1µF _{LBW = 186kHz}
O=1
100pF
f_LO = 4200MHz TO 6390MHz IN 190.7Hz STEPS
RF INPUT SIGNAL
LO IF
RF
IF OUTPUT
6948 TA01a
LTC6948-4 Phase Noise,
f_RF = 6236MHz
–90
–100
–110
–120
–130
RMS NOISE = 0.412°
–140 RMS JITTER = 183fs
f_PFD = 50MHz
–150 ^{LOOP BW = 186kHz}
INTN = 0
CPLE = 1
–160
100 1k 10k 100k 1M
OFFSET FREQUENCY (Hz)
10M 40M
6946 TA01b
For more information www.linear.com/LTC6948
6948f
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