MAX7377AXTP(2004) View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAX7377AXTP
(Rev.:2004)

Silicon Oscillator with Low-Power Frequency Switching

Maxim Integrated 

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

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

sensitive to its position on the board and does not need

to be placed right next to the µP. Refer to the microcon-

troller data sheet for clock-input compatibility with exter-

nal clock signals. The MAX7377 requires no biasing

components or load capacitance. When using the

MAX7377 to retrofit a crystal oscillator, remove all bias-

ing 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 jitter 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 res-

onator-based oscillator circuits.

Initial Power-Up and Operation

An internal power-up reset disables the oscillator until

VCC has risen above 2.2V. 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 qualifi-

cation is only performed 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 power-

supply voltage. Good power-supply decoupling is

needed to maintain the power-supply rejection perfor-

mance 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 microcon-

troller’s decoupling capacitor so that additional decou-

pling 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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