MAX7377 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAX7377

Silicon Oscillator with Low-Power Frequency Switching

Maxim Integrated 

MAX7377

Silicon Oscillator with Low-Power

Frequency Switching

VCC

MAX7377

600kHz TO 10MHz

(HF OSCILLATOR)

SPEED

LOGIC

POR

MUX

CLOCK

32kHz

(LF OSCILLATOR)

Figure 1. Functional Diagram

port that powers up in the input condition, connect a pullup

or pulldown resistor to the SPEED input to set the clock

to the preferred speed on power-up. The leakage current

through the resistor into the SPEED input is very low, so a

resistor value as high as 500kΩ may be used.

Applications Information

Interfacing to a Microcontroller

Clock Input

The MAX7377 clock output is a push-pull, CMOS, logic

output that directly drives any microprocessor (μP) or μC

clock input. There are no impedance-matching issues

when using the MAX7377. The MAX7377 is not sensi-

tive to its position on the board and does not need to be

placed right next to the μP. Refer to the microcontroller

data sheet for clock-input compatibility with external clock

signals. The MAX7377 requires no biasing components or

load capacitance. When using the MAX7377 to retrofit a

crystal oscillator, remove all biasing components from the

oscillator input.

Output Jitter

The MAX7377’s jitter performance is given in the Electrical

Characteristics table as a peak-to-peak value obtained

by observing the output of the MAX7377 for 20s with a

500MHz oscilloscope. Jitter values are approximately

proportional to the period of the output frequency of the

device. Thus, a 4MHz part has approximately twice the jit-

ter value of an 8MHz part. The jitter performance of clock

sources degrades in the presence of mechanical and

electrical interference. The MAX7377 is relatively immune

to vibration, shock, and EMI influences, and thus provides

a considerably more robust clock source than crystal or

ceramic resonator-based oscillator circuits.

Initial Power-Up and Operation

An internal power-up reset disables the oscillator until

VCC has risen above 2.57V. The clock then starts up

within 30μs (typ) at the frequency determined by the

SPEED pin.

Extended Temperature Operation

The MAX7377 was tested to +135°C during product

characterization and shown to function normally at this

temperature (see the Typical Operating Characteristics).

However, production test and qualification is only per-

formed from -40°C to +125°C at this time. Contact the

factory if operation outside this range is required.

Power-Supply Considerations

The MAX7377 operates with a 2.7V and 5.5V powersup-

ply voltage. Good power-supply decoupling is needed to

maintain the power-supply rejection performance of the

MAX7377. Bypass VCC to GND with a 0.1μF surface-

mount ceramic capacitor. Mount the bypass capacitor

as close to the device as possible. If possible, mount

the MAX7377 close to the microcontroller’s decoupling

capacitor so that additional decoupling is not required.

A larger value bypass capacitor is recommended if the

MAX7377 is to operate with a large capacitive load. Use

a bypass capacitor value of at least 1000 times that of the

output load capacitance.

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