MAXIM MAX7391 User Manual

General Description

The MAX7391 replaces ceramic resonators, crystals,
and supervisory functions for microcontrollers in 3.3V
and 5V applications.

The MAX7391 provides a clock source, reset, and
power-fail functions. The programmable power-fail func­tion provides early warning of power failure and is con­figurable to detect either an external voltage or the V

CC

supply to the device.

The clock output can be switched between normal and
half-speed operation. This functionality allows the micro­controller to operate at reduced power and may be
used to extend the time available to perform house­keeping tasks, such as writing data to flash during a
power failure. Connecting the power-fail output to the
SPEED input reduces clock speed automatically during
power-fail events.

The MAX7391 clock output is factory programmed to a
frequency in the 1MHz to 16MHz range. Four standard
frequencies are available. Other frequencies are avail­able upon request. The maximum operating supply cur­rent is 5.5mA (typ) with a clock frequency of 12MHz.

Unlike typical crystal and ceramic resonator oscillator
circuits, the MAX7391 is resistant to EMI and vibration,
and operates reliably at high temperatures. The high­output drive current and absence of high-impedance
nodes make the oscillator invulnerable to dirty or humid
operating conditions.

The MAX7391 is available in an 8-pin µMAX

®

package.
The MAX7391 standard operating temperature range is
from -40°C to +125°C.

Applications

White Goods

Automotive

Appliances and Controls

Handheld Products

Portable Equipment

Microcontroller Systems

Features

♦ Robust Microcontroller Clock and Supervisory

Functions in a Single Package

♦ Integrated Reset and Power-Fail Functions

♦ Speed Select

♦ +2.7V to +5.5V Operation

♦ Factory-Trimmed Oscillator

♦ Reset Valid Down to 1.1V Supply Voltage

♦ ±10mA Clock-Output Drive Current
♦ ±4% Total Accuracy for -40°C to +125°C

♦ ±2.75% Total Accurac for 0°C to +85°C

♦ 5.5mA Operating Current (12MHz Version)

♦ -40°C to +125°C Temperature Range

♦ Surface-Mount Package

♦ 1MHz to 16MHz Factory Preset Frequency Range

MAX7391

Speed-Switching Clock Generator

with Power Fail

________________________________________________________________ Maxim Integrated Products 1

19-3981; Rev 0; 1/06

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

SPEED

PFOGND

1

2

87CLOCK

RST/RSTV

CC

N.C.

PFI

TOP VIEW

µMAX

3

4

6

5

MAX7391

Pin Configuration

Ordering Information

Note: “s” is a placeholder for the reset output type. Insert the
symbol found in Table 2 in the place of “s.” “r” is a placeholder
for the power-on reset (POR) voltage. Insert the symbol found in
Table 1 in the place of “r.” “ff” is a placeholder for the nominal
output frequency. Insert the symbol found in Table 3 in the
place of “ff.” For example, MAX7391CMTP describes a device
with 4.38V reset level, open-collector

RST

output, and a clock

output frequency of 8MHz.

Typical Application Circuit, Functional Diagram, and Selector
Guide appear at end of data sheet.

µMAX is a registered trademark of Maxim Integrated Products, Inc.

PART TEMP RANGE PIN-PACKAGE

MAX7391srff -40°C to +125°C 8 µMAX U8-1

PKG

CODE

MAX7391

Speed-Switching Clock Generator
with Power Fail

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

VCCto GND...........................................................-0.3V to +6.0V

All Other Pins to GND ................................-0.3V to (V

CC

+ 0.3V)

CLOCK, RST/RST, PFO Output Current ..........................±50mA

Continuous Power Dissipation

8-Pin µMAX (derate 4.5mW/°C over T

A

= +70°C)........362mW

Operating Temperature Range .........................-40°C to +125°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

ELECTRICAL CHARACTERISTICS

(Typical Application Circuit, VCC= +2.7V to +5.5V, TA= -40°C to +125°C, 1MHz to 16MHz output frequency range, typical values at
V

CC

= +5.0V, TA= +25°C, unless otherwise noted.) (Note 1)

POWER REQUIREMENTS

Operating Supply Voltage V

Valid RST/RST Supply Voltage V

Operating Supply Current I

LOGIC INPUT: SPEED

Input Leakage Current I

Logic-Input High Voltage V

Logic-Input Low Voltage V

PUSH-PULL LOGIC OUTPUTS: RST/RST

Output High V

Output Low V

OPEN-DRAIN LOGIC OUTPUTS: RST, PFO

Output Low V

OUTPUT: CLOCK

CLOCK Output High Voltage V

CLOCK Output Low Voltage V

CLOCK Accuracy f

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

CC

CCR

LEAK

OLOISINK

OHCISOURCE

OLCISINK

CLOCK

Minimum supply voltage for valid RST/RST
output, T

f

= 12MHz 5.5

CC

OHISOURCE

OL

CLOCK

f

= 8MHz 4.5

CLOCK

Input is high 0.5 µA

IH

IL

I

= 3mA 0.05 0.4 V

SINK

= 3mA 0.05 0.4 V

= 5mA 0.3 V

Table 3, VCC = +5.0V -4 +4 %

2.7 5.5 V

= 0°C to +85°C

A

0.7 x V

CC

= 1mA VCC - 1.5 V

= 5mA VCC - 0.3 V

1.1 V

0.3 x V

CC

mA

V

V

MAX7391

Speed-Switching Clock Generator

with Power Fail

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(Typical Application Circuit, VCC= +2.7V to +5.5V, TA= -40°C to +125°C, 1MHz to 16MHz output frequency range, typical values at
V

CC

= +5.0V, TA= +25°C, unless otherwise noted.) (Note 1)

Note 1: All parameters are tested at TA= +25°C. Specifications over temperature are guaranteed by design.
Note 2: Guaranteed by design. Not production tested.

Clock Frequency Temperature
Coefficient

Clock Frequency Supply Voltage
Coefficient

CLOCK Duty Cycle (Note 2) 45 50 55 %

CLOCK Output Jitter

Output Rise Time t

Output Fall Time t

INTERNAL POWER-ON RESET

Reset Voltage

Reset Timeout Period t

POWER FAIL

Power-Fail Select Threshold V

VCC Monitoring Threshold
(Internal Threshold)

Internal Threshold Hysteresis V

PFI Monitoring Threshold
(External Threshold)

External Threshold Hysteresis V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

V

= +5.0V (Note 2) 140 400 ppm/°C

CC

= +25°C (Note 2) 0.67 1 %/V

T

A

Observation for 20s using a 500MHz
oscilloscope

C

R

(Note 2)

C

F

(Note 2)

V

TH+

V

RST

V

IHYSTVCC

V

ETH

EHYST

VCC rising, Table 1

VCC falling

TH-

Figure 1 86 135 250 µs

PFI input

SEL

VCC rising 4.06 4.38 4.60 V

ITH

PFI rising 0.9 1.1 1.4 V

PFI falling 1.0 3.5 8.0 %V

310

= 10pF, 10% to 90% of full scale

LOAD

= 10pF, 90% to 10% of full scale

LOAD

V

TA = +25°C

T

= -40°C to

A

+125°C

falling 1.0 2 4.0 %V

TH

- 1.5%

V

TH

- 2.5%

0.65 x
V

CC

2.5 7.0 ns

2.5 7.5 ns

V

TH

+ 1.5%

V

TH

+ 2.5%

0.98 x
V

TH+

0.85 x
V

CC

ps

RMS

V

V

ITH

ETH