SQUARE Phase Locked Loops (PLL) & Frequency Synthesis Circuits 844

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Part	Manufacturer	Other IC type	Temperature Grade	No. of Terminals	Package Code	Package Shape	Surface Mount	Package Body Material	Maximum Supply Current (Isup)	No. of Functions	Technology	Screening Level	Terminal Form	Nominal Supply Voltage (Vsup)	Power Supplies (V)	Maximum Output Frequency	Package Style (Meter)	Package Equivalence Code	Sub-Category	Terminal Pitch	Maximum Operating Temperature	Minimum Operating Temperature	Terminal Finish	Terminal Position	JESD-30 Code	Moisture Sensitivity Level (MSL)	Maximum Supply Voltage (Vsup)	Maximum Seated Height	Width (mm)	Qualification	Minimum Supply Voltage (Vsup)	Additional Features	JESD-609 Code	Maximum Time At Peak Reflow Temperature (s)	Peak Reflow Temperature (C)	Length
LMX2531LQX1910E	Texas Instruments	PLL FREQUENCY SYNTHESIZER	INDUSTRIAL	36	HVQCCN	SQUARE	YES	UNSPECIFIED		1	BICMOS		NO LEAD	3 V			CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel	TIN LEAD	QUAD	S-XQCC-N36	1	3.2 V	.8 mm	6 mm	Not Qualified	2.8 V		e0	30	235	6 mm
LMX2487SQ	Texas Instruments	PLL FREQUENCY SYNTHESIZER	INDUSTRIAL	24	HVQCCN	SQUARE	YES	PLASTIC/EPOXY		1			NO LEAD	3 V			CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel	TIN LEAD	QUAD	S-PQCC-N24	2	3.6 V	.8 mm	4 mm		2.5 V	QUADRUPLE MODULUS PRESCALER (RF):16/17/20/21 OR 32/33/36/37	e0	30	235	4 mm
LMX2433SLEX	Texas Instruments	PLL FREQUENCY SYNTHESIZER	INDUSTRIAL	20	VQCCN	SQUARE	YES	PLASTIC/EPOXY		1			NO LEAD	2.5 V			CHIP CARRIER, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel		QUAD	S-PQCC-N20	1	2.75 V	.6 mm	3.5 mm		2.25 V			30	260	3.5 mm
LMX2531LQE2820E/NOPB	Texas Instruments	PLL FREQUENCY SYNTHESIZER	INDUSTRIAL	36	HVQCCN	SQUARE	YES	PLASTIC/EPOXY	52 mA	1	BICMOS		NO LEAD	3 V	3	3132 GHz	CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE	LCC36,.25SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-PQCC-N36	3		.8 mm	6 mm	Not Qualified			e3	30	260	6 mm
LMX2515LQX0701	Texas Instruments	PLL FREQUENCY SYNTHESIZER	OTHER	28	VQCCN	SQUARE	YES	UNSPECIFIED	13.3 mA	1			NO LEAD	2.8 V	3		CHIP CARRIER, VERY THIN PROFILE	LCC28,.2SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-30 Cel	TIN LEAD	QUAD	S-XQCC-N28	2	3.3 V	.8 mm	5 mm	Not Qualified	2.5 V		e0		260	5 mm
LMX2515LQX1321	Texas Instruments	PLL FREQUENCY SYNTHESIZER	OTHER	28	VQCCN	SQUARE	YES	UNSPECIFIED	17.8 mA	1			NO LEAD	2.8 V	3		CHIP CARRIER, VERY THIN PROFILE	LCC28,.2SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-30 Cel	TIN LEAD	QUAD	S-XQCC-N28	2	3.3 V	.8 mm	5 mm	Not Qualified	2.5 V		e0		260	5 mm
LMX2531LQ1312E/NOPB	Texas Instruments	PLL FREQUENCY SYNTHESIZER	INDUSTRIAL	36	HVQCCN	SQUARE	YES	PLASTIC/EPOXY	49 mA	1	BICMOS		NO LEAD	3 V	3	3132 GHz	CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE	LCC36,.25SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-PQCC-N36	3		.8 mm	6 mm	Not Qualified			e3	30	260	6 mm
LMX2531LQ1415E	Texas Instruments	PLL FREQUENCY SYNTHESIZER	INDUSTRIAL	36	VQCCN	SQUARE	YES	UNSPECIFIED		1	BICMOS		NO LEAD	3 V			CHIP CARRIER, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-XQCC-N36	3	3.2 V	.8 mm	6 mm		2.8 V		e3	40	260	6 mm
LMX2313U	Texas Instruments	PLL FREQUENCY SYNTHESIZER	INDUSTRIAL	20	VFLGA	SQUARE	YES	UNSPECIFIED		1	BICMOS		BUTT	3 V			GRID ARRAY, VERY THIN PROFILE, FINE PITCH			.5 mm	85 Cel	-40 Cel		BOTTOM	S-XBGA-B20		5.5 V	.8 mm	3.5 mm		2.7 V	ALSO HAS INPUT DIVIDE RATIO FROM 56 TO 65535				3.5 mm
AD9901TE/883	Analog Devices	PHASE DETECTOR	MILITARY	20	QCCN	SQUARE	YES	CERAMIC, METAL-SEALED COFIRED		1		MIL-STD-883	NO LEAD	5 V	5/-5.2		CHIP CARRIER	LCC20,.35SQ	PLL or Frequency Synthesis Circuits	1.27 mm	125 Cel	-55 Cel	TIN LEAD	QUAD	S-CQCC-N20		5.5 V	2.54 mm	8.89 mm	Not Qualified	4.5 V	ALSO OPERATES AT -5.2 V SUPPLY	e0			8.89 mm
5962-9097901M2X	Analog Devices		MILITARY	20	QCCN	SQUARE	YES	CERAMIC, METAL-SEALED COFIRED		1			NO LEAD	5 V			CHIP CARRIER				125 Cel	-55 Cel		QUAD	S-CQCC-N20					Not Qualified		ALSO OPERATES AT -5.2 V SUPPLY
HMC1032LP6GE	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	40	HVQCCN	SQUARE	YES	PLASTIC/EPOXY		1			NO LEAD	3.3 V			CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-PQCC-N40	1	3.5 V	.9 mm	6 mm		3 V	ALSO OPERATES AT 5 V SUPPLY	e3			6 mm
AD9574BCPZ-REEL7	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	48	HVQCCN	SQUARE	YES	UNSPECIFIED		1			NO LEAD	3.3 V			CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel		QUAD	S-XQCC-N48	3	3.63 V	.8 mm	7 mm		2.97 V			30	260	7 mm
AD9852ASQ	Analog Devices	PLL FREQUENCY SYNTHESIZER	INDUSTRIAL	80	LQFP	SQUARE	YES	PLASTIC/EPOXY		1	CMOS		GULL WING	3.3 V			FLATPACK, LOW PROFILE			.65 mm	85 Cel	-40 Cel	TIN LEAD	QUAD	S-PQFP-G80	3	3.465 V	1.6 mm	14 mm	Not Qualified	3.135 V		e0		240	14 mm
HMC1032LP6GETR	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	40	QCCN	SQUARE	YES	PLASTIC/EPOXY	100 mA				NO LEAD		3.3,5		CHIP CARRIER	LCC40,.24SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-PQCC-N40	1				Not Qualified			e3	30	260
AD9959YSV	Analog Devices		INDUSTRIAL	56	QCCN	SQUARE	YES	PLASTIC/EPOXY			CMOS		NO LEAD		1.8,3.3		CHIP CARRIER	LCC56,.31SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel		QUAD	S-PQCC-N56					Not Qualified
HMC1034LP6GETR	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	40	QCCN	SQUARE	YES	PLASTIC/EPOXY					NO LEAD		3.3,5		CHIP CARRIER	LCC40,.24SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-PQCC-N40	1				Not Qualified			e3	30	260
AD9959YSV-REEL7	Analog Devices		INDUSTRIAL	56	QCCN	SQUARE	YES	PLASTIC/EPOXY			CMOS		NO LEAD		1.8,3.3		CHIP CARRIER	LCC56,.31SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel		QUAD	S-PQCC-N56					Not Qualified
AD9901TE	Analog Devices	PHASE DETECTOR	MILITARY	20	QCCN	SQUARE	YES	CERAMIC			BIPOLAR		NO LEAD		5/-5.2		CHIP CARRIER	LCC20,.35SQ	PLL or Frequency Synthesis Circuits	1.27 mm	125 Cel	-55 Cel	Tin/Lead (Sn/Pb)	QUAD	S-XQCC-N20					Not Qualified			e0
AD9852ASQZ	Analog Devices	PLL FREQUENCY SYNTHESIZER	INDUSTRIAL	80	LQFP	SQUARE	YES	PLASTIC/EPOXY		1	CMOS		GULL WING	3.3 V			FLATPACK, LOW PROFILE			.65 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-PQFP-G80		3.465 V	1.6 mm	14 mm	Not Qualified	3.135 V		e3			14 mm
AD9854AST	Analog Devices	PLL FREQUENCY SYNTHESIZER	INDUSTRIAL	80	LQFP	SQUARE	YES	PLASTIC/EPOXY		1	CMOS		GULL WING	3.3 V			FLATPACK, LOW PROFILE			.65 mm	85 Cel	-40 Cel	TIN LEAD	QUAD	S-PQFP-G80	3	3.465 V	1.6 mm	14 mm	Not Qualified	3.135 V		e0		240	14 mm
AD9901KPZ	Analog Devices	PHASE DETECTOR	COMMERCIAL	20	QCCJ	SQUARE	YES	PLASTIC/EPOXY		1	BIPOLAR		J BEND	5 V	5/-5.2		CHIP CARRIER	LDCC20,.4SQ	PLL or Frequency Synthesis Circuits	1.27 mm	70 Cel	0 Cel	MATTE TIN	QUAD	S-PQCC-J20	1	5.25 V	4.57 mm	8.9662 mm	Not Qualified	4.75 V	ALSO OPERATES AT -5.2 V SUPPLY	e3		260	8.9662 mm
5962-9097901M2A	Analog Devices	PHASE LOCKED LOOP	MILITARY	20	QCCN	SQUARE	YES	CERAMIC, METAL-SEALED COFIRED		1		MIL-STD-883	NO LEAD	5 V			CHIP CARRIER				125 Cel	-55 Cel	TIN LEAD	QUAD	S-CQCC-N20	1				Not Qualified		ALSO OPERATES AT -5.2 V SUPPLY	e0
HMC699LP5ERTR	Analog Devices		INDUSTRIAL	32	QCCN	SQUARE	YES	PLASTIC/EPOXY					NO LEAD	5 V	5		CHIP CARRIER	LCC32,.2SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel		QUAD	S-PQCC-N32					Not Qualified
V62/11606-01YB	Analog Devices		MILITARY	20	QCCN	SQUARE	YES	PLASTIC/EPOXY	13 mA		BICMOS		NO LEAD	3 V	3		CHIP CARRIER	LCC20,.16SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	125 Cel	-55 Cel		QUAD	S-PQCC-N20
HMC699LP5RTR	Analog Devices		INDUSTRIAL	32	QCCN	SQUARE	YES	PLASTIC/EPOXY					NO LEAD	5 V	5		CHIP CARRIER	LCC32,.2SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel		QUAD	S-PQCC-N32					Not Qualified
AD9954YSVZ-REEL	Analog Devices		INDUSTRIAL	48	QFP	SQUARE	YES	PLASTIC/EPOXY			CMOS		GULL WING	1.8 V	1.8		FLATPACK	TQFP48,.35SQ	PLL or Frequency Synthesis Circuits	.5 mm	105 Cel	-40 Cel	MATTE TIN	QUAD	S-PQFP-G48	3				Not Qualified			e3		260
AD9901KP	Analog Devices	PHASE DETECTOR	COMMERCIAL	20	QCCJ	SQUARE	YES	PLASTIC/EPOXY		1			J BEND	5 V	5/-5.2		CHIP CARRIER	LDCC20,.4SQ	PLL or Frequency Synthesis Circuits	1.27 mm	70 Cel	0 Cel	TIN LEAD	QUAD	S-PQCC-J20	1	5.25 V	4.57 mm	8.9662 mm	Not Qualified	4.75 V	ALSO OPERATES AT -5.2 V SUPPLY	e0		225	8.9662 mm
AD9852AST	Analog Devices	PLL FREQUENCY SYNTHESIZER	INDUSTRIAL	80	LQFP	SQUARE	YES	PLASTIC/EPOXY		1	CMOS		GULL WING	3.3 V			FLATPACK, LOW PROFILE			.65 mm	85 Cel	-40 Cel	TIN LEAD	QUAD	R-PQFP-G80	3	3.465 V	1.6 mm	14 mm	Not Qualified	3.135 V		e0		240	14 mm
AD9574BCPZ	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	48	HVQCCN	SQUARE	YES	UNSPECIFIED		1			NO LEAD	3.3 V			CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel		QUAD	S-XQCC-N48	3	3.63 V	.8 mm	7 mm		2.97 V			30	260	7 mm
AD9958YSV	Analog Devices		INDUSTRIAL	56	QCCN	SQUARE	YES	PLASTIC/EPOXY					NO LEAD		1.8,3.3		CHIP CARRIER	LCC56,.31SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel		QUAD	S-PQCC-N56					Not Qualified
AD9854ASQ	Analog Devices	PLL FREQUENCY SYNTHESIZER	INDUSTRIAL	80	HLQFP	SQUARE	YES	PLASTIC/EPOXY		1	CMOS		GULL WING	3.3 V			FLATPACK, HEAT SINK/SLUG, LOW PROFILE			.65 mm	85 Cel	-40 Cel	TIN LEAD	QUAD	S-PQFP-G80	3	3.465 V	1.6 mm	14 mm	Not Qualified	3.135 V		e0		240	14 mm
AD9901KP-REEL	Analog Devices	PHASE DETECTOR	COMMERCIAL	20	QCCJ	SQUARE	YES	PLASTIC/EPOXY		1	BIPOLAR		J BEND	5 V	5/-5.2		CHIP CARRIER	LDCC20,.4SQ	PLL or Frequency Synthesis Circuits	1.27 mm	70 Cel	0 Cel	TIN LEAD	QUAD	S-PQCC-J20	1	5.25 V	4.57 mm	8.9662 mm	Not Qualified	4.75 V	ALSO OPERATES AT -5.2 V SUPPLY	e0		225	8.9662 mm
AD9958YSV-REEL7	Analog Devices		INDUSTRIAL	56	QCCN	SQUARE	YES	PLASTIC/EPOXY					NO LEAD		1.8,3.3		CHIP CARRIER	LCC56,.31SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel		QUAD	S-PQCC-N56					Not Qualified
AD9901TE/883B	Analog Devices	PHASE LOCKED LOOP	MILITARY	20	QCCN	SQUARE	YES	CERAMIC, METAL-SEALED COFIRED		1	BIPOLAR		NO LEAD	5 V	5/-5.2		CHIP CARRIER	LCC20,.35SQ	PLL or Frequency Synthesis Circuits	1.27 mm	125 Cel	-55 Cel	TIN LEAD	QUAD	S-CQCC-N20		5.5 V	2.54 mm	8.89 mm	Not Qualified	4.5 V		e0			8.89 mm
AD9901KPZ-REEL	Analog Devices	PHASE DETECTOR	COMMERCIAL	20	QCCJ	SQUARE	YES	PLASTIC/EPOXY		1	BIPOLAR		J BEND	5 V	5/-5.2		CHIP CARRIER	LDCC20,.4SQ	PLL or Frequency Synthesis Circuits	1.27 mm	70 Cel	0 Cel	MATTE TIN	QUAD	S-PQCC-J20	1	5.25 V	4.57 mm	8.9662 mm	Not Qualified	4.75 V	ALSO OPERATES AT -5.2 V SUPPLY	e3		260	8.9662 mm
AD9954YSV-REEL	Analog Devices		INDUSTRIAL	48	QFP	SQUARE	YES	PLASTIC/EPOXY			CMOS		GULL WING	1.8 V	1.8		FLATPACK	TQFP48,.35SQ	PLL or Frequency Synthesis Circuits	.5 mm	105 Cel	-40 Cel		QUAD	S-PQFP-G48					Not Qualified
MAX2880ETP+T	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	20	HVQCCN	SQUARE	YES	UNSPECIFIED		1			NO LEAD	3.3 V			CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel	Matte Tin (Sn) - annealed	QUAD	S-XQCC-N20	1	3.6 V	.8 mm	4 mm		2.8 V		e3	30	260	4 mm
MAX2880ETP+	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	20	HVQCCN	SQUARE	YES	UNSPECIFIED		1			NO LEAD	3.3 V			CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel	Matte Tin (Sn) - annealed	QUAD	S-XQCC-N20	1	3.6 V	.8 mm	4 mm		2.8 V		e3	30	260	4 mm
HMC828LP6CE	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	40	HVQCCN	SQUARE	YES	PLASTIC/EPOXY		1			NO LEAD	3.3 V			CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-PQCC-N40	1	3.5 V	.9 mm	6 mm	Not Qualified	3 V	IT ALSO OPERATES WITH 4.8V-5.2V SUPPLY	e3		260	6 mm
HMC831LP6CE	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	40	HVQCCN	SQUARE	YES	PLASTIC/EPOXY		1			NO LEAD	3.3 V			CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-PQCC-N40	1	3.5 V	.9 mm	6 mm	Not Qualified	3 V		e3			6 mm
HMC783LP6CE	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	40	HVQCCN	SQUARE	YES	PLASTIC/EPOXY		1			NO LEAD	3.3 V			CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-PQCC-N40	3	3.45 V	.9 mm	6 mm	Not Qualified	3 V		e3	30	260	6 mm
HMC831LP6CETR	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	40	QCCN	SQUARE	YES	PLASTIC/EPOXY					NO LEAD		3.3,5		CHIP CARRIER	LCC40,.24SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel		QUAD	S-PQCC-N40					Not Qualified				NOT SPECIFIED	NOT SPECIFIED
HMC764LP6CE	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	40	HVQCCN	SQUARE	YES	PLASTIC/EPOXY		1			NO LEAD	3.3 V			CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE			.5 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-PQCC-N40	3	3.45 V	.9 mm	6 mm	Not Qualified	3 V		e3		260	6 mm
HMC820LP6CETR	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	40	QCCN	SQUARE	YES	PLASTIC/EPOXY					NO LEAD		3.3,5		CHIP CARRIER	LCC40,.24SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel		QUAD	S-PQCC-N40					Not Qualified				NOT SPECIFIED	NOT SPECIFIED
HMC840LP6CETR	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	40	QCCN	SQUARE	YES	PLASTIC/EPOXY					NO LEAD		3.3,5		CHIP CARRIER	LCC40,.24SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-PQCC-N40	1				Not Qualified			e3	30	260
HMC700LP4RTR	Analog Devices		INDUSTRIAL	24	QCCN	SQUARE	YES	PLASTIC/EPOXY	110 mA		BICMOS		NO LEAD		3.3,5		CHIP CARRIER	LCC24,.16SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel		QUAD	S-PQCC-N24					Not Qualified
HMC828LP6CETR	Analog Devices	PHASE LOCKED LOOP	INDUSTRIAL	40	QCCN	SQUARE	YES	PLASTIC/EPOXY					NO LEAD		3.3,5		CHIP CARRIER	LCC40,.24SQ,20	PLL or Frequency Synthesis Circuits	.5 mm	85 Cel	-40 Cel	MATTE TIN	QUAD	S-PQCC-N40	1				Not Qualified			e3		260

Phase Locked Loops (PLL) & Frequency Synthesis Circuits

Phase Locked Loops (PLL) and Frequency Synthesis Circuits are electronic circuits used to generate and control stable and precise frequencies for use in various applications, such as communication systems, signal processing, and instrumentation.

A PLL is a feedback system that compares the phase of an input signal to the phase of a reference signal and adjusts the output frequency to match the reference frequency. The basic components of a PLL include a phase detector, a low-pass filter, a voltage-controlled oscillator (VCO), and a frequency divider. The phase detector compares the phase of the input and reference signals and generates an error signal that is filtered and used to adjust the frequency of the VCO. The output of the VCO is divided by a frequency divider to generate the output frequency. PLLs are commonly used for frequency synthesis, clock recovery, and phase modulation/demodulation.

Frequency synthesis circuits are electronic circuits used to generate precise and stable frequencies by combining multiple signals with different frequencies. These circuits use various techniques, such as direct digital synthesis (DDS), fractional-N synthesis, and frequency mixing to generate frequencies. DDS is a technique that uses a digital signal generator to generate a waveform with a specific frequency, phase, and amplitude. Fractional-N synthesis is a technique that uses a PLL to generate a frequency that is a fraction of the reference frequency. Frequency mixing is a technique that combines two signals with different frequencies to generate a signal with a frequency equal to the difference between the two frequencies.

PLLs and frequency synthesis circuits are critical components in many electronic systems that require precise and stable frequencies. These circuits are used in communication systems, signal processing, instrumentation, and other applications where accurate frequency generation and control is required.