19-3896; Rev 1; 1/06
System Monitoring Oscillator with
Watchdog and Power Fail
General Description
The MAX7387/MAX7388 replace ceramic resonators,
crystals, and supervisory functions for microcontrollers
in 3.3V and 5V applications.
The MAX7387/MAX7388 provide a clock source together
with integrated reset, watchdog, and power-fail func-
tions. The watchdog timer is pin programmable and
provides watchdog timeout values in the 16ms to
2048ms range. The power-fail output provides early
warning of power failure. The power-fail threshold on the
MAX7388 is internally set. The MAX7387 also provides
a separate watchdog output that is used as a status
indicator or to control safety-critical system elements.
The MAX7387/MAX7388 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 (max) with a clock frequency of
12MHz.
Unlike typical crystal and ceramic resonator oscillator
circuits, the MAX7387/MAX7388 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 MAX7387/MAX7388 are available in 10-pin and 8-pin
µMAX
®
packages, respectively. The MAX7387/MAX7388
standard operating temperature range is from -40°C to
+125°C.
Features
♦
Robust Microcontroller Clock and Supervisor in a
Single Package
♦
Integrated Reset, Watchdog, and Power-Fail
Functions
♦
Pin-Programmable Watchdog Timeout
♦
+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
♦
-40°C to +125°C Temperature Range
♦
8- and 10-Pin µMAX Surface-Mount Packages
♦
5.5mA Operating Current (12MHz)
♦
1MHz to 16MHz Factory Preset Frequency
MAX7387/MAX7388
Ordering Information
PART
TEMP RANGE
o
o
o
o
PIN-PACKAGE PKG CODE
U10-2
U8-1
MAX7387srff
-40 C to +125 C 10 µMAX
MAX7388srff
-40 C to +125 C 8 µMAX
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, MAX7387CMTP 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
PFI 1
V
CC
WDS1
WDS2
GND
2
3
4
5
10 CLOCK
9
RST/RST
WDI
PFO
WDO
WDS2
3
TOP VIEW
V
CC
1
8
7
CLOCK
RST/RST
WDI
PFO
MAX7387
WDS1 2
8
7
6
MAX7388
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.
System Monitoring Oscillator with
Watchdog and Power Fail
MAX7387/MAX7388
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,
PFO
Output Current, RST/RST, WDO.................±50mA
Continuous Power Dissipation (T
A
= +70°C)
10-Pin µMAX (derate 5.6mW/°C over +70°C) ..............444mW
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)
(Note 2)
45
-2.75
-4
140
0.67
50
V
CC
- 0.3
0.3
+2.75
+4
400
1
55
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
CLOCK Duty Cycle
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
_______________________________________________________________________________________
System Monitoring Oscillator with
Watchdog and Power Fail
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 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
WDS1 = GND, WDS2 = open
Watchdog Timeout Period
(Figure 2)
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
CONDITIONS
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)
MIN
TYP
310
2.5
2.8
7.0
7.5
MAX
UNITS
ps
RMS
MAX7387/MAX7388
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
System Monitoring Oscillator with
Watchdog and Power Fail
MAX7387/MAX7388
Typical Operating Characteristics
(Typical
Application Circuit,
V
CC
= +5V, T
A
= +25°C, unless otherwise noted.)
FREQUENCY vs. SUPPLY VOLTAGE
MAX7387/88 toc01
FREQUENCY vs. TEMPERATURE
MAX7387/88 toc02
DUTY CYCLE vs. SUPPLY VOLTAGE
MAX7387/88 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
2.90
3.55
4.20
V
CC
(V)
4.85
5.50
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
DUTY CYCLE vs. TEMPERATURE
MAX7387/88 toc04
CLOCK OUTPUT WAVEFORM
WITH C
L
= 10pF
MAX7387/88 toc05
CLOCK OUTPUT WAVEFORM
WITH C
L
= 50pF
MAX7387/88 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
MAX7387/88 toc07
SUPPLY CURRENT vs. TEMPERATURE
MAX7387/88 toc08
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX7387/88 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
_______________________________________________________________________________________
System Monitoring Oscillator with
Watchdog and Power Fail
MAX7387/MAX7388
Typical Operating Characteristics (continued)
(Typical
Application Circuit,
V
CC
= +5V, T
A
= +25°C, unless otherwise noted.)
CLOCK SETTLING TIME FROM START
MAX7387/88 toc10
POWER-ON RESET BEHAVIOR
MAX7387/88 toc11
MAXIMUM V
CC
TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
MAX7387/88 toc12
1000
V
CC
2V/div
V
CC
2V/div
TRANSIENT DURATION (µs)
RESET OCCURS ABOVE THIS CURVE
100
CLOCK
2V/div
CLOCK
5V/div
t
RST
RST
5V/div
PFI = V
CC
PFO
5V/div
10
V
CC
FALLING FROM V
TH+
+ 100mV
1
100 200 300 400 500 600 700 800 900 1000
RESET THRESHOLD OVERDRIVE (mV)
1µs/div
100µs/div
RESPONSE OF RST AND WDO
WDI EXCEEDING t
WDG
RISING THRESHOLD vs. TEMPERATURE
MAX7387/88 toc14
MAX7387/88 toc13
2.90
WDI
2V/div
2.88
t
WDG
V
TH+
(V)
WDO
5V/div
RST
5V/div
t
RST
2.86
2.84
2.82
2.80
2ms/div
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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