Silicon Oscillator with Low-Power

Frequency Switching and Reset Output

6

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Detailed Description

The MAX7378 is a dual-speed clock generator with

integrated reset for microcontrollers and UARTs in 3V,

3.3V, and 5V applications (Figure 1). The MAX7378 is a

replacement for two crystal-oscillator modules, crystals,

or ceramic resonators and a system-reset IC. The high-

speed clock frequency is factory trimmed to specific

values. A variety of popular standard frequencies are

available (Table 2). The low-speed clock frequency is

fixed at 32.768kHz (Figure 1). No external components

are required for setting or adjusting the frequency.

Supply Voltage

The MAX7378 has been designed for use in systems

with nominal supply voltages of 3V, 3.3V, or 5V and is

specified for operation with supply voltages in the 2.7V

to 5.5V range. See the Absolute Maximum Ratings sec-

tion for limit values of power-supply and pin voltages.

Oscillator

The clock output is a push-pull configuration and is

capable of driving a ground-connected 500

Ω or a posi-

tive-supply connected 250

Ω 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 when switching between high- and

low-speed modes. A typical startup characteristic is

shown in the Typical Operating Characteristics.

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. See the RST Reset Output Options section for more details.

5

CLOCK

Push-Pull Clock Output

6

GND

Ground

7

ENABLE

Active-High Clock Enable Input. See the ENABLE Input section for more details.

8N. C.

No Connect. No internal connection.

LOW-SPEED TO HIGH-SPEED

TRANSITION

MAX7378 toc19

CLOCK

SPEED

20

µs/div

LOW-SPEED TO HIGH-SPEED TRANSITION

(EXPANDED SCALE)

MAX7378 toc20

CLOCK

SPEED

400

µs/div

Typical Operating Characteristics (continued)