Maxim Integrated Clock Generators 424

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Part RoHS Manufacturer Peripheral IC Type Temperature Grade Terminal Form No. of Terminals Package Code Package Shape Package Body Material Surface Mount Maximum Supply Voltage Screening Level Address Bus Width Maximum Output Clock Frequency DAC Channels Power Supplies (V) Package Style (Meter) Package Equivalence Code Minimum Supply Voltage Maximum Operating Temperature Minimum Operating Temperature Terminal Finish ADC Channels Terminal Position DMA Channels Maximum Seated Height Width Additional Features External Data Bus Width Maximum Time At Peak Reflow Temperature (s) Peak Reflow Temperature (C) Length Total Dose (V) Technology Maximum Supply Current Nominal Supply Voltage PWM Channels Sub-Category ROM Programmability Terminal Pitch JESD-30 Code Moisture Sensitivity Level (MSL) Qualification Speed Nominal Primary Clock/Crystal Frequency JESD-609 Code No. of I/O Lines

DS1077LZ-60

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

SOP

RECTANGULAR

PLASTIC/EPOXY

YES

3.6 V

60 MHz

SMALL OUTLINE

2.7 V

85 Cel

-40 Cel

TIN LEAD

DUAL

1.75 mm

3.9 mm

245

4.9 mm

CMOS

3 V

1.27 mm

R-PDSO-G8

1

Not Qualified

e0

DS1089LU-21G+

Maxim Integrated

CLOCK GENERATOR, OTHER

MATTE TIN

30

260

1

e3

DS1089LU-21G

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

3.6 V

14.7456 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

85 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

CMOS

3.3 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

MAX7391CXWB

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

16 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

DS1077U-133+

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.25 V

133.333 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

4.75 V

85 Cel

-40 Cel

MATTE TIN

DUAL

1.1 mm

3 mm

30

260

3 mm

CMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e3

DS1087LU-466/T

Maxim Integrated

CLOCK GENERATOR, OTHER

GULL WING

8

RECTANGULAR

PLASTIC/EPOXY

YES

3.6 V

66.6 MHz

2.7 V

85 Cel

-40 Cel

DUAL

CMOS

15 mA

3.3 V

R-PDSO-G8

.4 MHz

MAX7391CMRD

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

4 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

DS1077U-100+W

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

SOP

SQUARE

PLASTIC/EPOXY

YES

5.25 V

100 MHz

SMALL OUTLINE

4.75 V

85 Cel

-40 Cel

MATTE TIN

DUAL

IT ALSO OPERATES AT 0.1MHZ PRIMARY CLOCK FREQUENCY IN STANDARD MODE

30

260

CMOS

5 V

S-PDSO-G8

1

.4 MHz

e3

DS1075Z-100IND

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

SOP

RECTANGULAR

PLASTIC/EPOXY

YES

5.5 V

100 MHz

SMALL OUTLINE

4.5 V

85 Cel

-40 Cel

TIN LEAD

DUAL

1.75 mm

3.9 mm

4.9 mm

CMOS

5 V

1.27 mm

R-PDSO-G8

1

Not Qualified

50 MHz

e0

DS4M133D+33

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

NO LEAD

10

HQCCN

RECTANGULAR

CERAMIC, METAL-SEALED COFIRED

YES

3.465 V

133.33 MHz

CHIP CARRIER, HEAT SINK/SLUG

3.135 V

85 Cel

-40 Cel

QUAD

1.62 mm

3.2 mm

NOT SPECIFIED

NOT SPECIFIED

5 mm

BIPOLAR

3.3 V

1 mm

R-CQCC-N10

DS4M125P+33

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

NO LEAD

10

HQCCN

RECTANGULAR

CERAMIC, METAL-SEALED COFIRED

YES

3.465 V

125 MHz

CHIP CARRIER, HEAT SINK/SLUG

3.135 V

85 Cel

-40 Cel

QUAD

1.62 mm

3.2 mm

NOT SPECIFIED

NOT SPECIFIED

5 mm

BIPOLAR

3.3 V

1 mm

R-CQCC-N10

DS1075Z-100+

Maxim Integrated

CLOCK GENERATOR, OTHER

COMMERCIAL

GULL WING

8

SOP

RECTANGULAR

PLASTIC/EPOXY

YES

5.25 V

100 MHz

SMALL OUTLINE

4.75 V

70 Cel

0 Cel

MATTE TIN

DUAL

1.75 mm

3.9 mm

30

260

4.9 mm

CMOS

5 V

1.27 mm

R-PDSO-G8

1

Not Qualified

50 MHz

e3

DS1088LU-02/W

Maxim Integrated

CLOCK GENERATOR, OTHER

OTHER

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

3.6 V

2.048 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

85 Cel

-20 Cel

DUAL

1.1 mm

3 mm

NOT SPECIFIED

NOT SPECIFIED

3 mm

CMOS

3.3 V

.65 mm

S-PDSO-G8

MAX7391CJRD

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

4 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

MAX9491EUD

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

14

TSSOP

RECTANGULAR

PLASTIC/EPOXY

YES

3.6 V

200 MHz

3.3

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

TSSOP14,.25

3 V

85 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

4.4 mm

5 mm

CMOS

3.3 V

Clock Generators

.65 mm

R-PDSO-G14

1

Not Qualified

27 MHz

e0

MAX7391BJWB

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

16 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

DS1077U-125/T&R

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.25 V

125 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

4.75 V

85 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

CMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

DS1077Z-133+

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

SOP

RECTANGULAR

PLASTIC/EPOXY

YES

5.25 V

133.333 MHz

SMALL OUTLINE

4.75 V

85 Cel

-40 Cel

MATTE TIN

DUAL

1.75 mm

3.9 mm

30

260

4.9 mm

CMOS

5 V

1.27 mm

R-PDSO-G8

1

Not Qualified

e3

DS1077U-133/T&R

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.25 V

133.333 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

4.75 V

85 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

CMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

MAX7391AMRD

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

4 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

MAX7391CXTP

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

8 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

MAX7391CQVB

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

12 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

DS1089LU-22F

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

3.6 V

24.576 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

85 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

CMOS

3.3 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

MAX7391BNRD

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

4 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

DS1091LUA-055/V+T

Maxim Integrated

CLOCK GENERATOR, OTHER

MATTE TIN

30

260

CMOS

1

e3

DS1077LU-60+

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

3.6 V

60 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

85 Cel

-40 Cel

MATTE TIN

DUAL

1.1 mm

3 mm

30

260

3 mm

CMOS

3 V

.65 mm

S-PDSO-G8

1

Not Qualified

e3

DS1075-100IND

Maxim Integrated

CLOCK GENERATOR, OTHER

THROUGH-HOLE

8

RECTANGULAR

PLASTIC/EPOXY

NO

IN-LINE

DUAL

4.572 mm

7.62 mm

9.375 mm

CMOS

2.54 mm

R-PDIP-T8

Not Qualified

DS1077LZ-66+T&R

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

SOP

RECTANGULAR

PLASTIC/EPOXY

YES

3.6 V

66.66 MHz

SMALL OUTLINE

2.7 V

85 Cel

-40 Cel

MATTE TIN

DUAL

1.75 mm

3.9 mm

4.9 mm

CMOS

3 V

1.27 mm

R-PDSO-G8

1

Not Qualified

e3

DS1077Z-203

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

SOP

RECTANGULAR

PLASTIC/EPOXY

YES

5.25 V

100 MHz

SMALL OUTLINE

4.75 V

85 Cel

-40 Cel

TIN LEAD

DUAL

1.75 mm

3.9 mm

4.9 mm

CMOS

5 V

1.27 mm

R-PDSO-G8

1

Not Qualified

e0

DS1077U-100/T&R

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.25 V

100 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

4.75 V

85 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

CMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

DS1087LU-23C/T&R

Maxim Integrated

CLOCK GENERATOR, OTHER

GULL WING

8

RECTANGULAR

PLASTIC/EPOXY

YES

3.6 V

2.7 V

85 Cel

-40 Cel

DUAL

CMOS

15 mA

3.3 V

R-PDSO-G8

.4 MHz

DS4M133P+33

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

NO LEAD

10

HQCCN

RECTANGULAR

CERAMIC, METAL-SEALED COFIRED

YES

3.465 V

133.33 MHz

CHIP CARRIER, HEAT SINK/SLUG

3.135 V

85 Cel

-40 Cel

QUAD

1.62 mm

3.2 mm

NOT SPECIFIED

NOT SPECIFIED

5 mm

BIPOLAR

3.3 V

1 mm

R-CQCC-N10

DS1088LU-02

Maxim Integrated

CLOCK GENERATOR, OTHER

OTHER

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

3.6 V

2.048 MHz

3/3.3

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

TSSOP8,.19

2.7 V

85 Cel

-20 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

CMOS

24 mA

3.3 V

Clock Generators

.65 mm

S-PDSO-G8

1

Not Qualified

e0

DS1077U-120

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.25 V

120 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

4.75 V

85 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

CMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

MAX7391BPWB

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

16 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

MAX7391BXWB

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

16 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

DS1085LZ-12

Maxim Integrated

CLOCK GENERATOR, OTHER

COMMERCIAL

GULL WING

8

SOP

RECTANGULAR

PLASTIC/EPOXY

YES

3.6 V

66 MHz

SMALL OUTLINE

3 V

70 Cel

0 Cel

TIN LEAD

DUAL

1.75 mm

3.9 mm

4.9 mm

CMOS

3.3 V

1.27 mm

R-PDSO-G8

1

Not Qualified

e0

MAX7391CNTP

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

8 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

MAX7391CNWB

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

16 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

MAX7391ASTP

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

8 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

DS1086HU-C02+

Maxim Integrated

CLOCK GENERATOR, OTHER

MATTE TIN

30

260

CMOS

1

e3

DS1087LU-450+

Maxim Integrated

CLOCK GENERATOR, OTHER

GULL WING

8

RECTANGULAR

PLASTIC/EPOXY

YES

3.6 V

2.7 V

85 Cel

-40 Cel

MATTE TIN

DUAL

30

260

CMOS

15 mA

3.3 V

R-PDSO-G8

1

.4 MHz

MAX7391BSRD

Maxim Integrated

CLOCK GENERATOR, OTHER

AUTOMOTIVE

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

5.5 V

4 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

125 Cel

-40 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

BICMOS

5 V

.65 mm

S-PDSO-G8

1

Not Qualified

e0

DS1088LU-16

Maxim Integrated

CLOCK GENERATOR, OTHER

OTHER

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

3.6 V

16.6 MHz

3/3.3

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

TSSOP8,.19

2.7 V

85 Cel

-20 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

CMOS

24 mA

3.3 V

Clock Generators

.65 mm

S-PDSO-G8

1

Not Qualified

e0

MAX9471ETP+

Maxim Integrated

CLOCK GENERATOR, OTHER

INDUSTRIAL

NO LEAD

20

HVQCCN

SQUARE

UNSPECIFIED

YES

3.6 V

200 MHz

3.3

CHIP CARRIER, HEAT SINK/SLUG, VERY THIN PROFILE

LCC20,.20SQ,25

3 V

85 Cel

-40 Cel

MATTE TIN

QUAD

.8 mm

5 mm

30

260

5 mm

CMOS

3.3 V

Clock Generators

.65 mm

S-XQCC-N20

1

Not Qualified

27 MHz

e3

DS1088LU-16+T

Maxim Integrated

CLOCK GENERATOR, OTHER

OTHER

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

3.6 V

16.6 MHz

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

2.7 V

85 Cel

-20 Cel

MATTE TIN

DUAL

1.1 mm

3 mm

30

260

3 mm

CMOS

3.3 V

.65 mm

S-PDSO-G8

1

Not Qualified

e3

DS1075Z-60

Maxim Integrated

CLOCK GENERATOR, OTHER

COMMERCIAL

GULL WING

8

SOP

RECTANGULAR

PLASTIC/EPOXY

YES

5.25 V

60 MHz

SMALL OUTLINE

4.75 V

70 Cel

0 Cel

TIN LEAD

DUAL

1.75 mm

3.9 mm

4.9 mm

CMOS

5 V

1.27 mm

R-PDSO-G8

Not Qualified

50 MHz

e0

DS1088LU-100/T

Maxim Integrated

CLOCK GENERATOR, OTHER

OTHER

GULL WING

8

TSSOP

SQUARE

PLASTIC/EPOXY

YES

3.6 V

100 MHz

3/3.3

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

TSSOP8,.19

2.7 V

85 Cel

-20 Cel

TIN LEAD

DUAL

1.1 mm

3 mm

3 mm

CMOS

24 mA

3.3 V

Clock Generators

.65 mm

S-PDSO-G8

Not Qualified

e0

Clock Generators

A clock generator is an electronic circuit that generates an electrical signal that serves as a timing reference for other circuits in a system. Clock generators are used in many electronic devices, such as computers, cell phones, and digital cameras. The clock signal is used to synchronize the operation of different components in the system, such as microprocessors, memory devices, and input/output interfaces.

Clock generators can be classified based on their output frequency and stability. Some clock generators produce a fixed frequency output, while others have a programmable output frequency. The stability of the clock signal is also an important parameter, and clock generators can be designed to produce a stable frequency output over a wide range of temperature and voltage conditions.

Clock generators can also include additional features such as frequency multiplication, frequency division, and phase locking. Frequency multiplication allows the output frequency to be multiplied by an integer value, while frequency division allows the output frequency to be divided by an integer value. Phase locking is used to ensure that the output frequency of the clock generator is synchronized with an external reference signal.