Detailed Description

The MAX7384 is a dual-speed clock generator with inte-

grated reset for microcontrollers (µCs) and UARTs in 3V,

3.3V, and 5V applications. The MAX7384 is a replace-

ment for crystal-oscillator modules, crystals, or ceramic

resonators and a system reset IC. The high-speed clock

frequency and reset threshold voltage are factory

trimmed to specific values (see Table 1). A variety of

popular standard frequencies are available. The low-

speed clock frequency is fixed at 32.768kHz; see Table

2. No external components are required for setting or

adjusting the frequency.

Oscillator

The push-pull clock output drives a load to within

400mV of either supply rail. The clock output remains

stable over the full operating voltage range and does

not generate short output cycles during either power-on

or changing of the frequency. A typical oscillating start-

up is shown in the Typical Operating Characteristics.

Clock-Speed Selection

Drive SPEED low to select slow clock speed (nominally

32.768kHz) or high to select full clock speed. SPEED can

clock speed, or connected to a logic output (such as a µP

GPIO port) used to change clock speed on the fly. If

SPEED is connected to a µP GPIO port, connect a pullup

or pulldown resistor to set the clock to the preferred

speed on power-up. SPEED input bias current is 2µA

(max), so a resistor value as high as 500kΩ can be used.

Applications Information

Interfacing to a Microcontroller

Clock Input

The MAX7384 clock output is a push-pull, CMOS, logic

output that directly drives a µP or µC clock input. There

are no impedance-matching issues when using the

MAX7384. Refer to the microcontroller data sheet for

clock input compatibility with external clock signals.

The MAX7384 requires no biasing components or load

capacitance. When using the MAX7384 to retrofit a

crystal oscillator, remove all biasing components from

the oscillator input.

Reset Output

The MAX7384 is available with three reset output stage

options: push-pull active low, push-pull active high, and

open-drain active low. RST is asserted when the moni-

and remains asserted for 120µs after the monitored input

RST output requires an external pullup resistor.

Output Jitter

The MAX7384’s jitter performance is given in the

Electrical Characteristics table as a peak-to-peak value

obtained by observing the output of the MAX7384 for

Silicon Oscillator with Low-Power Frequency

Switching and Reset Output

6

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MAX7384

RST

CLOCK

10MHz TO 16MHz

(HF OSCILLATOR)

POR

GND

32kHz

(LF OSCILLATOR)

MUX

LOGIC

SPEED

Figure 1. Functional Diagram

Pin Description

PIN

NAME

FUNCTION

3

SPEED

Clock-Speed Select Input. Drive SPEED low to select the 32kHz fixed frequency. Drive SPEED high

to select factory-trimmed frequency.

4

RST

Reset Output. Open-drain or push-pull output. See the Ordering Information.

5

CLOCK

Push-Pull Clock Output

6

GND

Ground

7

E.C.

Externally Connected. Connect to Vcc.

8

N.C.

No Connection. Not internally connected.