19-3897; Rev 1; 2/06
Microcontroller Clock Generator with
Watchdog
General Description
The MAX7389/MAX7390 replace ceramic resonators,
crystals, and supervisory functions for microcontrollers
in 3.3V and 5V applications.
The MAX7389/MAX7390 provide a clock source, reset,
and watchdog functions. The watchdog timer is pin pro-
grammable and provides watchdog timeout values in
the 16ms to 2048ms range. The MAX7389 provides a
separate watchdog output that is used as a status indi-
cator or to control safety-critical system elements.
The MAX7390 features a clock-speed select that
reduces the output frequency by half. This functionality
allows the microcontroller to operate at reduced power
and may be used to extend the time available to per-
form housekeeping tasks, such as writing data to flash
during a power failure.
The MAX7389/MAX7390 clock outputs are factory pro-
grammed to a frequency in the 1MHz to 16MHz range.
Four standard frequencies are available. Other frequen-
cies are available upon request. The maximum operating
supply current is 5.5mA with a clock frequency of 12MHz.
Unlike typical crystal and ceramic resonator oscillator
circuits, the MAX7389/MAX7390 are resistant to EMI
and vibration, and operate reliably at high tempera-
tures. The high-output drive current and absence of
high-impedance nodes make the oscillator invulnerable
to dirty or humid operating conditions.
The MAX7389/MAX7390 are available in an 8-pin µMAX
®
package. The MAX7389/MAX7390 standard operating
temperature range is from -40°C to +125°C.
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
Features
♦
Robust Microcontroller Clock and Supervisor in a
Single Package
Integrated Reset and Watchdog Functions
Pin-Programmable Watchdog Timeout
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 Accuracy for 0°C to +85°C
5.5mA Operating Current (12MHz Version)
MAX7389/MAX7390
♦
-40°C to +125°C Temperature Range
♦
8-Pin µMAX Surface-Mount Package
♦
1MHz to 16MHz Factory Preset Frequency
Ordering Information
PART
MAX7389srff
MAX7390srff
TEMP RANGE
-40
o
C to +125
o
C
-40 C to +125 C
o
o
PIN-
PACKAGE
8 µMAX
8 µMAX
PKG
CODE
U8-1
U8-1
Applications
White Goods
Automotive
Appliances and Controls
Handheld Products
Portable Equipment
Microcontroller Systems
Note:
“s” is a placeholder for the reset output type. Insert the
symbol found in Table 3 in the place of “s.” “r” is a placeholder
for the power-on reset (POR) voltage. Insert the symbol found in
Table 2 in the place of “r.” “ff” is a placeholder for the nominal
output frequency. Insert the symbol found in Table 4 in the
place of “ff.” For example, MAX7389CMTP 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.
Pin Configurations
TOP VIEW
V
CC
WDS1
WDS2
1
2
8
7
CLOCK
RST/RST
WDI
WDO
TOP VIEW
V
CC
1
8
7
CLOCK
RST/RST
WDI
SPEED
MAX7389
3
6
5
GND 4
WDS1 2
MAX7390
WDS2
3
6
5
GND 4
µMAX
µMAX
1
________________________________________________________________
Maxim Integrated Products
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.
Microcontroller Clock Generator with
Watchdog
MAX7389/MAX7390
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ...........................................................-0.3V to +6.0V
All Other Pins to GND ................................-0.3V to (V
CC
+ 0.3V)
CLOCK, RST/RST,
WDO
Output Current .........................±50mA
Continuous Power Dissipation (T
A
= +70°C)
8-Pin µMAX (derate 4.5mW/°C over +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
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.
ELECTRICAL CHARACTERISTICS
(Typical
Application Circuit,
V
CC
= +2.7V to +5.5V, T
A
= -40°C to +125°C, 1MHz to 16MHz output frequency range, typical values at
V
CC
= +5.0V, T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
POWER REQUIREMENTS
Operating Supply Voltage
Valid RST/RST Supply Voltage
Operating Supply Current
V
CC
V
CCR
I
CC
T
A
= 0°C to +85°C
T
A
= -40°C to +125°C
f
CLOCK
= 12MHz
f
CLOCK
= 8MHz
V
CC
- 0.55V
0.9
V
CC
- 1.1V
0.45
I
LEAK
V
IH
V
IL
V
OH
V
OL
V
OLO
V
OHC
V
OLC
f
CLOCK
I
SOURCE
= 1mA
I
SINK
= 3mA
I
SINK
= 3mA
I
SOURCE
= 5mA
I
SINK
= 5mA
T
A
= 0°C to +85°C, V
CC
= 5.0V
T
A
= -40°C to +125°C, V
CC
= 5.0V
V
CC
= 5.0V (Note 2)
T
A
= +25°C (Note 2)
-2.75
-4
140
0.67
V
CC
- 0.3
0.3
+2.75
+4
400
1
V
CC
- 1.5
0.05
0.05
0.4
0.4
Input high
0.7 x V
CC
0.3 x V
CC
0.5
2.7
5.5
1.1
1.18
5.5
4.5
V
V
mA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
TRI-LEVEL ANALOG INPUTS: WDS1, WDS2
Input-High Voltage Level
Input-Middle Voltage Level
Input-Low Voltage Level
LOGIC INPUT: WDI
Input Leakage Current
Logic-Input High Voltage
Logic-Input Low Voltage
Output High
Output Low
Output Low
OUTPUT: CLOCK
Output High Voltage
Output Low Voltage
CLOCK Accuracy
Clock Frequency Temperature
Coefficient
Clock Frequency Supply Voltage
Coefficient
V
V
%
ppm/°C
%/V
µA
V
V
V
V
V
V
V
V
PUSH-PULL LOGIC OUTPUTS: RST/RST
OPEN-DRAIN LOGIC OUTPUTS:
RST, PFO, WDO
2
_______________________________________________________________________________________
Microcontroller Clock Generator with
Watchdog
ELECTRICAL CHARACTERISTICS (continued)
(Typical
Application Circuit,
V
CC
= +2.7V to +5.5V, T
A
= -40°C to +125°C, 1MHz to 16MHz output frequency range, typical values at
V
CC
= +5.0V, T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
CLOCK Duty Cycle
CLOCK Output Jitter
Output Rise Time
Output Fall Time
INTERNAL POWER-ON RESET
T
A
= +25°C
V
TH+
Reset Voltage
V
TH-
Reset Timeout Period
WATCHDOG
WDS1 = GND, WDS2 = GND
WDS1 = open, WDS2 = GND
WDS1 = V
CC
, WDS2 = GND
Watchdog Timeout Period
(Figure 2)
WDS1 = GND, WDS2 = open
t
WDG
WDS1 = open, WDS2 = open
WDS1 = V
CC
, WDS2 = open
WDS1 = GND, WDS2 = V
CC
WDS1 = open, WDS2 = V
CC
WDS1 = WDS2 = V
CC
(watchdog disabled)
POWER FAIL
Power-Fail Select Threshold
V
CC
Monitoring Threshold
(Internal Threshold)
Internal Threshold Hysteresis
PFI Monitoring Threshold
(External Threshold)
External Threshold Hysteresis
V
SEL
V
ITH
V
IHYST
V
ETH
V
EHYST
PFI input
V
CC
rising
V
CC
falling
PFI rising
PFI falling
0.65 x
V
CC
4.06
1.0
0.9
1.0
4.38
2
1.1
3.5
0.85 x
V
CC
4.60
4.0
1.4
8.0
V
V
%V
ITH
V
%V
ETH
11
22
44
88
177
354
708
1416
16
32
64
128
256
512
1024
2048
22
44
88
177
354
708
1416
2832
ms
t
RST
V
CC
falling
Figures 1, 2
86
V
CC
rising, Table 2
T
A
= -40°C to +125°C
V
TH
- 1.5%
V
TH
- 2.5%
0.98 x
V
TH+
135
250
µs
V
TH
+ 1.5%
V
TH
+ 2.5%
V
t
R
t
F
SYMBOL
(Note 2)
Observation for 20s using a 500MHz
oscilloscope
C
LOAD
= 10pF, 10% to 90% of full scale (Note 2)
C
LOAD
= 10pF, 90% to 10% of full scale (Note 2)
CONDITIONS
MIN
45
TYP
50
310
2.5
2.8
7.0
7.5
MAX
55
UNITS
%
ps
RMS
MAX7389/MAX7390
ns
ns
Note 1:
All parameters are tested at T
A
= +25°C. Specifications over temperature are guaranteed by design.
Note 2:
Guaranteed by design. Not production tested.
_______________________________________________________________________________________
3
Microcontroller Clock Generator with
Watchdog
MAX7389/MAX7390
Typical Operating Characteristics
(Typical
Application Circuit,
V
CC
= +5V, f
CLOCK
= 16MHz, T
A
= +25°C, unless otherwise noted.)
FREQUENCY vs. SUPPLY VOLTAGE
MAX7389 toc01
FREQUENCY vs. TEMPERATURE
MAX7389 toc02
DUTY CYCLE vs. SUPPLY VOLTAGE
MAX7389 toc03
1.020
1.040
1.030
NORMALIZED FREQUENCY
1.020
1.010
1.000
0.990
0.980
NORMALIZED TO T
A
= +25°C
52
NORMALIZED FREQUENCY
1.010
51
DUTY CYCLE (%)
1.000
50
0.990
NORMALIZED TO V
CC
= +5V
V
TH+
= +2.9V
0.980
2.90
3.55
4.20
V
CC
(V)
4.85
5.50
49
V
TH+
= +2.9V
48
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
2.90
3.55
4.20
V
CC
(V)
4.85
5.50
DUTY CYCLE vs. TEMPERATURE
MAX7389 toc04
CLOCK OUTPUT WAVEFORM
WITH C
L
= 10pF
MAX7389 toc05
CLOCK OUTPUT WAVEFORM
WITH C
L
= 50pF
MAX7389 toc06
52
V
CC
= +3.3V
V
CC
= +3.3V
51
DUTY CYCLE (%)
50
CLOCK
1V/div
CLOCK
1V/div
49
48
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
40ns/div
40ns/div
CLOCK OUTPUT WAVEFORM
WITH C
L
= 100pF
MAX7389 toc07
SUPPLY CURRENT vs. TEMPERATURE
MAX7389 toc08
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX7389 toc09
5
5
4
I
CC
(mA)
CLOCK
1V/div
V
CC
= +5V
4
I
CC
(mA)
3
V
CC
= +3.3V
2
3
2
V
TH+
= +2.9V
1
40ns/div
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
1
2.90
3.55
4.20
V
CC
(V)
4.85
5.50
4
_______________________________________________________________________________________
Microcontroller Clock Generator with
Watchdog
MAX7389/MAX7390
Typical Operating Characteristics (continued)
(Typical
Application Circuit,
V
CC
= +5V, f
CLOCK
= 16MHz, T
A
= +25°C, unless otherwise noted.)
CLOCK SETTLING TIME FROM START
MAX7389 toc10
POWER-ON RESET BEHAVIOR
MAX7389/90 toc11
V
CC
2V/div
V
CC
2V/div
CLOCK
2V/div
t
RST
CLOCK
5V/div
RST
5V/div
1µs/div
100µs/div
MAXIMUM V
CC
TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
MAX7389 toc12
RESPONSE OF RST AND WDO
WDI EXCEEDING t
WDG
1000
MAX7389/90 toc13
TRANSIENT DURATION (µs)
RESET OCCURS ABOVE THIS CURVE
100
t
WDG
WDI
2V/div
WDO
5V/div
RST
5V/div
t
RST
10
V
CC
FALLING FROM V
TH+
+ 100mV
1
100 200 300 400 500 600 700 800 900 1000
RESET THRESHOLD OVERDRIVE (mV)
2ms/div
RISING THRESHOLD vs. TEMPERATURE
MAX7389 toc14
CLOCK RESPONSE TO SPEED SELECT INPUT
MAX7389/90 toc15
2.90
2.88
SPEED
2V/div
V
TH+
(V)
2.86
2.84
CLOCK
2V/div
2.82
2.80
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
200ns/div
_______________________________________________________________________________________
5
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