19-3981; Rev 0; 1/06
Speed-Switching Clock Generator
with Power Fail
General Description
The MAX7391 replaces ceramic resonators, crystals,
and supervisory functions for microcontrollers in 3.3V
and 5V applications.
Features
♦ Robust Microcontroller Clock and Supervisory
Functions in a Single Package
♦ Integrated Reset and Power-Fail Functions
♦ Speed Select
The MAX7391 provides a clock source, reset, and
power-fail functions. The programmable power-fail func-
tion provides early warning of power failure and is con-
♦ +2.7V to +5.5V Operation
figurable to detect either an external voltage or the V
supply to the device.
CC
♦ Factory-Trimmed Oscillator
♦ Reset Valid Down to 1.1V Supply Voltage
♦ ±1ꢀmꢁ Clock-Output Drive Current
♦ ±±4 Total ꢁccuracy ꢂor -±ꢀ0C to +1250C
The clock output can be switched between normal and
half-speed operation. This functionality allows the micro-
controller to operate at reduced power and may be
used to extend the time available to perform house-
keeping 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.
♦ ±2.754 Total ꢁccurac ꢂor ꢀ0C to +ꢃ50C
♦ 5.5mꢁ Operating Current (12MHz Version)
♦ -±ꢀ0C to +1250C Temperature Range
♦ Surꢂace-Mount Package
The MAX7391 clock output is factory programmed to a
frequency in the 1MHz to 16MHz range. Four standard
frequencies are available. Other frequencies are avail-
able upon request. The maximum operating supply cur-
rent is 5.5mA (typ) with a clock frequency of 12MHz.
♦ 1MHz to 16MHz Factory Preset Frequency Range
Unlike typical crystal and ceramic resonator oscillator
circuits, the MAX7391 is resistant to EMI and vibration,
and operates reliably at high temperatures. The high-
output drive current and absence of high-impedance
nodes make the oscillator invulnerable to dirty or humid
operating conditions.
Ordering Information
PKG
CODE
PꢁRT
TEMP RꢁNGE
PIN-PꢁCKꢁGE
MAX7391srff -40°C to +125°C 8 µMAX
U8-1
The MAX7391 is available in an 8-pin µMAX® package.
The MAX7391 standard operating temperature range is
from -40°C to +125°C.
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.
Applications
White Goods
Automotive
Appliances and Controls
Handheld Products
Portable Equipment
Microcontroller Systems
Pin Configuration
TOP VIEW
PFI
1
2
3
4
8
7
6
5
CLOCK
RST/RST
SPEED
PFO
V
CC
MAX7391
Typical Application Circuit, Functional Diagram, and Selector
Guide appear at end of data sheet.
N.C.
GND
µMAX is a registered trademark of Maxim Integrated Products, Inc.
µMꢁX
________________________________________________________________ Maxim Integrated Products
1
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.