19-3350; Rev 0; 7/04
Silicon Oscillator with Low-Power
Frequency Switching and Reset Output
The MAX7378 dual-speed silicon oscillator with reset, is
a replacement for ceramic resonators, crystals, crystaloscillator modules, and discrete reset circuits. The
MAX7378 provides the primary and secondary clock
source and reset function for microcontrollers in 3V,
3.3V, and 5V applications. The MAX7378 features a
factory-programmed high-speed oscillator, a
32.768kHz oscillator, a clock selector input, and a
microprocessor (µP) power-on-reset (POR) supervisor.
The clock output can be switched at any time between
the high-speed clock and the 32.768kHz clock for lowpower operation. Switchover is synchronized internally
to provide glitch-free clock switching.
Unlike typical crystal and ceramic resonator oscillator
circuits, the MAX7378 is resistant to vibration and EMI.
The high-output-drive current and absence of highimpedance nodes make the oscillator less susceptible
to dirty or humid operating conditions. With a wide
operating temperature range as standard, the
MAX7378 is a good choice for demanding home appliance, industrial, and automotive environments.
The MAX7378 is available in an 8-pin µMAX® package.
Refer to the MAX7384 data sheet for frequencies
≥10MHz. The MAX7378 standard operating temperature range is -40°C to +125°C. See the Applications
Information section for the extended operating temperature range.
Applications
White Goods
Automotive
Consumer Products
Appliances and Controls
Handheld Products
Portable Equipment
Microcontroller (µC) Systems
Features
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
2.7V to 5.5V Operation
Accurate High-Speed Oscillator: 600kHz to 10MHz
Accurate Low-Speed 32kHz Oscillator
Glitch-Free Switch Between High Speed and Low
Speed at Any Time
Reset Output Holds the µC in Reset for 100µs
After Clock Startup
±10mA Clock-Output Drive Capability
2% Initial Accuracy
±50ppm/°C Temperature Coefficient
50% ±7% Output Duty Cycle
5ns Output Rise and Fall Time
Low Jitter: 160ps (Peak-to-Peak) at 8MHz
2.4mA Fast-Mode Operating Current (8MHz)
11µA Slow-Mode Operating Current (32kHz)
-40°C to +125°C Temperature Range
Ordering Information
PART
TEMP RANGE
RESET
OUTPUT
MAX7378A _ _ _
-40oC to +125oC
Active high
push-pull
8 µMAX
MAX7378B _ _ _
-40oC to +125oC
Active low
push-pull
8 µMAX
MAX7378C _ _ _ -40oC to +125oC Open drain
PINPACKAGE
8 µMAX
Standard version is shown in bold. The first letter after the part
number designates the reset output option. Insert the letter corresponding to the desired reset threshold level from Table 1 in
the next position. Insert the two-letter code from Table 2 in the
remaining two positions for the desired frequency range. See
Table 3 for standard part numbers.
Typical Application Circuit
SUPPLY VOLTAGE
VCC
VL
ENABLE
OSC1
CLOCK
Pin Configuration appears at end of data sheet.
OSC2
MAX7378
RST
µC
RST/RST
I/O PORT
SPEED
µMAX is a registered trademark of Maxim Integrated Products, Inc.
________________________________________________________________ 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.
1
MAX7378
General Description
MAX7378
Silicon Oscillator with Low-Power
Frequency Switching and Reset Output
ABSOLUTE MAXIMUM RATINGS
VCC to GND .............................................................-0.3V to +6V
All Other Pins to GND ................................-0.3V to (VCC + 0.3V)
CLOCK Current ................................................................±10mA
Continuous Power Dissipation (TA = +70°C)
8-Pin µMAX (derate 4.5mW/°C above +70°C)....362mW (U8-1)
Operating Temperature Range .........................-40°C to +135°C
Junction Temperature .....................................................+150°C
Storage Temperature Range.............................-60°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
(VCC = 2.7V to 5.5V, VL = VCC, TA = -40°C to +125°C, unless otherwise noted. Typical values are at VCC = 5V, TA = +25°C.) (Note 1)
PARAMETER
Operating Supply Voltage
Logic Output Supply Voltage
Operating Supply Current
Shutdown Current
SYMBOL
CONDITIONS
VCC
VL
Must be connected to VCC
MIN
TYP
MAX
UNITS
2.7
5.5
V
2.7
5.5
V
mA
ICC + IL
fCLOCK = 8MHz, no load
2.4
5.5
ICC + IL
fCLOCK = 32.768kHz, no load
11
25
µA
ENABLE = 0V; ICC + IL
3.0
7.5
µA
ISHDN
LOGIC INPUT (SPEED, ENABLE)
0.7 x
VCC
Input High Voltage
VIH
V
Input Low Voltage
VIL
0.3 x
VCC
V
Input Current
IIN
2
µA
CLOCK OUTPUT
Output High Voltage
Output Low Voltage
Initial Fast CLOCK Frequency
Accuracy
Slow CLOCK Frequency
Temperature Sensitivity
2
VL 0.4
VL = 2.7V, ISOURCE = 2.5mA
VL 0.4
VOH
VOL
fFCLOCK
Fast CLOCK Frequency
Temperature Sensitivity
Initial Slow CLOCK Frequency
Accuracy
VL = 4.5V, ISOURCE = 9mA
V
VL = 4.5V, ISINK = 20mA
0.4
VL = 2.7V, ISINK = 10mA
0.4
VCC = 5V, TA = +25°C (Note 2)
-2
+2
VCC = 2.7V to 5.5V, TA = +25°C
-4
+4
(Note 3)
fSCLOCK
VCC = 5V, TA = +25°C
32.440
VCC = 2.7V to 5.5V, TA = +25°C
31.785
(Note 3)
±50
±325
32.768
33.096
33.751
±50
_______________________________________________________________________________________
±325
V
%
ppm/oC
kHz
ppm/oC
Silicon Oscillator with Low-Power
Frequency Switching and Reset Output
(VCC = 2.7V to 5.5V, VL = VCC, TA = -40°C to +125°C, unless otherwise noted. Typical values are at VCC = 5V, TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
CLOCK Output Duty Cycle
MIN
TYP
MAX
UNITS
43
50
57
%
Observation of 8MHz output for 20s using a
500MHz oscilloscope
CLOCK Output Jitter
160
psP-P
CLOCK Output Rise Time
tR
10% to 90%
5
ns
CLOCK Output Fall Time
tF
90% to 10%
5
ns
RST/RST OUTPUT
Reset Threshold
VTH+
Reset Hysteresis
VTHYS
POR Delay
TA = +25°C
VTH 1.5%
VTH +
1.5%
TA = -40°C to +125°C
VTH 5%
VTH +
5%
V
VCC rising
VHYST = {(VTH+) - ( VTH-)}/(VTH-) x 100%
VCC rising from 0V to (VTH +200mV) in 1µs
Output High Voltage
VOH
Output Low Voltage
VOL
VL = 4.5V, ISOURCE = 9mA
VL - 0.4
VL = 2.7V, ISOURCE = 2.5mA
VL - 0.4
2.0
%
100
µs
V
VL = 4.5V, ISINK = 20mA
0.4
VL = 2.7V, ISINK = 10mA
0.4
V
Note 1: All parameters are tested at TA = +25°C. Specifications over temperature are guaranteed by design.
Note 2: The frequency is determined by part number selection. See the Ordering Information.
Note 3: Guaranteed by design. Not production tested.
_______________________________________________________________________________________
3
MAX7378
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VCC = VL = 5V, TA = +25°C, unless otherwise noted.)
DUTY CYCLE vs. TEMPERATURE
53
49
51
50
49
47
CLOCK = 32kHz
47
-55
-30
-5
20
45
70
95
-30
-5
DUTY CYCLE vs. SUPPLY VOLTAGE
70
95
4.3
120
51
50
49
48
13.0
1.4
12.5
12.0
11.5
11.0
46
10.5
45
10.0
4.6
4.9
5.2
5.5
-30
-5
20
45
70
95
-55
120
9
1.3
-5
20
8
1.1
1.0
0.9
0.8
70
95
120
34.5
CLOCK = 32kHz
34.0
33.5
33.0
32.5
32.0
31.5
31.0
30.5
CLOCK = 4MHz
0.5
5.5
45
FREQUENCY vs. SUPPLY VOLTAGE
FREQUENCY (kHz)
1.2
0.6
CLOCK = 32kHz
SUPPLY VOLTAGE (V)
-30
35.0
MAX7378 toc08
1.4
0.7
5.2
0.8
SUPPLY CURRENT vs. SUPPLY VOLTAGE
SUPPLY CURRENT (mA)
10
4.9
0.9
TEMPERATURE (°C)
1.5
MAX7378 toc07
11
4.6
1.0
TEMPERATURE (°C)
12
4.3
1.1
0.5
-55
SUPPLY CURRENT vs. SUPPLY VOLTAGE
13
1.2
0.6
SUPPLY VOLTAGE (V)
14
CLOCK = 4 MHz
0.7
CLOCK = 32kHz
CLOCK = 4MHz
5.5
5.2
1.3
SUPPLY CURRENT (mA)
52
4.9
SUPPLY CURRENT vs. TEMPERATURE
1.5
MAX7378 toc05
13.5
SUPPLY CURRENT (µA)
53
4.3
4.6
SUPPLY VOLTAGE (V)
14.0
MAX7378 toc04
54
DUTY CYCLE (%)
45
SUPPLY CURRENT vs. TEMPERATURE
55
4
20
TEMPERATURE (°C)
TEMPERATURE (°C)
47
CLOCK = 32kHz
45
-55
120
49
46
45
45
50
47
CLOCK = 4MHz
46
46
51
48
48
48
52
MAX7378 toc06
50
53
MAX7378 toc09
51
52
54
DUTY CYCLE (%)
52
54
DUTY CYCLE (%)
DUTY CYCLE (%)
53
55
MAX7378 toc02
MAX7378 toc01
54
DUTY CYCLE vs. SUPPLY VOLTAGE
55
MAX7378 toc03
DUTY CYCLE vs. TEMPERATURE
55
SUPPLY CURRENT (µA)
MAX7378
Silicon Oscillator with Low-Power
Frequency Switching and Reset Output
30.0
4.3
4.6
4.9
SUPPLY VOLTAGE (V)
5.2
5.5
4.3
4.6
4.9
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5.2
5.5
Silicon Oscillator with Low-Power
Frequency Switching and Reset Output
FREQUENCY vs. TEMPERATURE
32.8
4.02
4.00
3.98
32.7
32.6
32.5
32.4
3.96
32.3
3.94
32.2
3.92
32.1
3.90
4.6
4.9
5.5
5.2
SUPPLY VOLTAGE (V)
4.02
4.00
3.98
CLOCK = 4MHz
3.92
3.90
-55
-30
-5
20
45
70
95
-55
120
-30
-5
20
45
120
MAX7378 toc15
F = 4MHz, CL = 50pF
F = 4MHz, CL = 100pF
40ns/div
40ns/div
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD
HIGH-SPEED TO LOW-SPEED
TRANSITION
40ns/div
HIGH-SPEED TO LOW-SPEED
TRANSITION (EXPANDED SCALE)
MAX7378 toc17
MAX7378 toc18
MAX7378 toc16
1000
95
CLOCK OUTPUT WAVEFORM (CL = 100pF)
MAX7378 toc14
F = 4MHz, CL = 10pF
70
TEMPERATURE (°C)
CLOCK OUTPUT WAVEFORM (CL = 50pF)
MAX7378 toc13
MAXIMUM TRANSIENT DURATION (µs)
4.04
3.94
TEMPERATURE (°C)
CLOCK OUTPUT WAVEFORM (CL = 10pF)
4.06
3.96
CLOCK = 32kHz
32.0
4.3
4.08
FREQUENCY (MHz)
4.04
32.9
FREQUENCY (kHz)
FREQUENCY (MHz)
4.06
FREQUENCY vs. TEMPERATURE
4.10
MAX7378 toc11
MAX7378 toc10
CLOCK = 4MHz
4.08
33.0
MAX7378 toc12
FREQUENCY vs. SUPPLY VOLTAGE
4.10
RESET OCCURS
ABOVE THE CURVE
100
CLOCK
CLOCK
SPEED
SPEED
RESET = 4.29V
10
0
200
400
600
800
1000
20µs/div
400µs/div
RESET THRESHOLD OVERDRIVE (mV)
_______________________________________________________________________________________
5
MAX7378
Typical Operating Characteristics (continued)
(VCC = VL = 5V, TA = +25°C, unless otherwise noted.)
MAX7378
Silicon Oscillator with Low-Power
Frequency Switching and Reset Output
Typical Operating Characteristics (continued)
(VCC = VL = 5V, TA = +25°C, unless otherwise noted.)
LOW-SPEED TO HIGH-SPEED
TRANSITION
LOW-SPEED TO HIGH-SPEED TRANSITION
(EXPANDED SCALE)
MAX7378 toc19
MAX7378 toc20
CLOCK
CLOCK
SPEED
SPEED
20µs/div
400µs/div
Pin Description
PIN
NAME
1
VCC
2
VL
3
FUNCTION
Positive Supply Voltage. Bypass VCC to GND with a 0.1µF capacitor.
Output Supply Voltage. Connect VL to VCC. Bypass VL to GND with a 0.1µF capacitor.
Clock Speed-Select Input. Drive SPEED low to select the 32kHz fixed frequency. Drive SPEED high to
select factory-trimmed frequency.
SPEED
4
RST
5
CLOCK
Reset Output. See the RST Reset Output Options section for more details.
6
GND
7
ENABLE
8
N. C.
Push-Pull Clock Output
Ground
Active-High Clock Enable Input. See the ENABLE Input section for more details.
No Connect. No internal connection.
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 highspeed 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.
6
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 section 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 500Ω or a positive-supply connected 250Ω 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.
_______________________________________________________________________________________
Silicon Oscillator with Low-Power
Frequency Switching and Reset Output
VL
Interfacing to a Microcontroller
Clock Input
MAX7378
32kHz
(LF OSCILLATOR)
POR
RST/RST
SPEED
MUX
LOGIC
CLOCK
ENABLE
The MAX7378 clock output is a push-pull, CMOS logic
output that directly drives any µP or µC clock input.
There are no impedance-matching issues when using
the MAX7378. The MAX7378 is not sensitive to its position on the board and does not need to be placed right
next to the µP. Connect the MAX7378 VL pin and µC (or
other clock-input device) to the same supply voltage
level. Refer to the µC data sheet for clock-input compatibility with external clock signals. The MAX7378 requires
no biasing components or load capacitance. When
using the MAX7378 to retrofit a crystal oscillator, remove
all biasing components from the oscillator input.
RST Reset Output Options
The MAX7378 is available with three reset output stage
options: push-pull with active-low output, push-pull with
active-high output, and open drain with active-low output. The RST output is asserted when the monitored
input (VCC) drops below the internal VTH- threshold and
remains asserted for 100µs after the monitored input
exceeds the internal VTH+ threshold. The open-drain
RST output requires an external pullup resistor.
600kHz TO 10MHz
(HF OSCILLATOR)
Figure 1. Functional Diagram
ENABLE Input
The MAX7378 has an active-high enable input that controls the clock and reset outputs. The clock output is
driven high when disabled. The reset asserts when disabled (low for active-low reset, high for active-high
reset). Drive ENABLE low to disable the clock output on
the next rising edge. Drive ENABLE high to activate the
clock output.
Clock-Speed Select Input
The MAX7378 uses logic input pin, SPEED, to set clock
speed. Take this pin low to select slow clock speed
(nominally 32.768kHz) or high to select full clock
speed. The SPEED input may be strapped to VCC or to
GND to select fast or slow clock speed, or connected
to a logic output (such as a processor port) used to
change clock speed on the fly. If the SPEED input is
connected to a processor port that powers up in the
input condition, connect a pullup or pulldown resistor to
the SPEED input to set the clock to the preferred speed
on power-up. The leakage current through the resistor
into the SPEED input is very low, so a resistor value as
high as 500kΩ may be used.
Output Jitter
The MAX7378’s jitter performance is given in the
Electrical Characteristics table as a peak-to-peak value
obtained by observing the output of the MAX7378 for
20s with a 500MHz oscilloscope. Jitter values are
approximately proportional to the period of the output
frequency of the device. Thus, a 4MHz part has
approximately twice the jitter value of an 8MHz part.
The jitter performance of clock sources degrades in the
presence of mechanical and electrical interference.
The MAX7378 is relatively immune to vibration, shock,
and EMI influences, and thus provides a considerably
more robust clock source than crystal or ceramic resonator-based oscillator circuits.
Initial Power-Up and Operation
An intial power-up reset holds the reset output active for
100µs (typ). However, the clock starts up within 30µs
(typ) at the frequency determined by the SPEED pin.
Power-Supply Brownout
The RST output is asserted whenever VCC drops below
the specified threshold level. The action of VCC dropping below the reset threshold and then rising back
above the threshold asserts RST and starts a normal
_______________________________________________________________________________________
7
MAX7378
Applications Information
VCC
MAX7378
Silicon Oscillator with Low-Power
Frequency Switching and Reset Output
power-on reset cycle. The MAX7378 reset circuit features internal hysteresis that creates two trip points: one
for rising supply voltage and one for falling supply voltage. The standard threshold values (see Table 1) are
the trip points for rising supply voltage. The trip point
for falling supply voltage is calculated by subtracting
the hysteresis value from the rising supply trip point.
The hysteresis prevents the reset output from oscillating (chattering) when VCC is near the voltage threshold.
The reset circuit is immune to short transient VCC drops
(see Maximum Transient Duration vs. Reset Threshold
in the Typical Operating Characteristics).
Extended Temperature Operation
The MAX7378 was tested to +135°C during product
characterization and shown to function normally at
this temperature (see the Typical Operating Characteristics). However, production test and qualification is only
performed from -40°C to +125°C at this time. Contact the
factory if operation outside this range is required.
Power-Supply Considerations
The MAX7378 operates with a 2.7V and 5.5V powersupply voltage. There are two power-supply pins, VCC
and VL. V CC provides the main power input to the
device and VL supplies the clock and reset output circuits. Good power-supply decoupling is needed to
maintain the power-supply rejection performance of the
MAX7378. Bypass both V CC and VL to GND with a
0.1µF surface-mount ceramic capacitor. Mount the
bypassing capacitors as close to the device as possible. If possible, mount the MAX7378 close to the µC’s
decoupling capacitor so that additional decoupling is
not required. A larger value bypass capacitor is recommended if the MAX7378 is to operate with a large
capacitive load. Use a bypass capacitor value of at
least 1000 times that of the output load capacitance.
Note: VL must be equal to VCC.
Pin Configuration
Table 1. Standard Reset Threshold Levels
SUFFIX
RESET THRESHOLD (V)
R
2.57
M
4.29
For all other reset threshold options, contact the factory.
Table 2. Standard Frequencies
SUFFIX
STANDARD FREQUENCY (MHz)
MG
1
OK
1.8432
QT
3.39545
QW
3.6864
RD
4
RH
4.1943
TOP VIEW
VCC
1
8
VL
2
7
ENABLE
SPEED
3
6
GND
RST
4
5
CLOCK
MAX7378
µMAX
TP
8
For all other frequency options, contact the factory.
8
_______________________________________________________________________________________
N.C.
Silicon Oscillator with Low-Power
Frequency Switching and Reset Output
MAX7378
Table 3. Standard Part Numbers
PART
PIN-PACKAGE
RESET OUTPUT TYPE
RESET THRESHOLD (V)
MAX7378CRMG
8 µMAX
Open drain
2.57
FREQUENCY (MHZ)
1
MAX7378CROK
8 µMAX
Open drain
2.57
1.8432
MAX7378CRQT
8 µMAX
Open drain
2.57
3.39545
MAX7378CRQW
8 µMAX
Open drain
2.57
3.6864
MAX7378CRRD
8 µMAX
Open drain
2.57
4
MAX7378CRRH
8 µMAX
Open drain
2.57
4.1943
MAX7378CRTP
8 µMAX
Open drain
2.57
8
MAX7378CMMG
8 µMAX
Open drain
4.29
1
MAX7378CMOK
8 µMAX
Open drain
4.29
1.8432
MAX7378CMQT
8 µMAX
Open drain
4.29
3.39545
MAX7378CMQW
8 µMAX
Open drain
4.29
3.6864
MAX7378CMRD
8 µMAX
Open drain
4.29
4
MAX7378CMRH
8 µMAX
Open drain
4.29
4.1943
MAX7378CMTP
8 µMAX
Open drain
4.29
8
Chip Information
TRANSISTOR COUNT: 2027
PROCESS: BiCMOS
_______________________________________________________________________________________
9
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
4X S
8
8
INCHES
DIM
A
A1
A2
b
E
ÿ 0.50±0.1
H
c
D
e
E
H
0.6±0.1
L
1
1
α
0.6±0.1
S
BOTTOM VIEW
D
MIN
0.002
0.030
MAX
0.043
0.006
0.037
0.014
0.010
0.007
0.005
0.120
0.116
0.0256 BSC
0.120
0.116
0.198
0.188
0.026
0.016
6∞
0∞
0.0207 BSC
8LUMAXD.EPS
MAX7378
Silicon Oscillator with Low-Power
Frequency Switching and Reset Output
MILLIMETERS
MAX
MIN
0.05
0.75
1.10
0.15
0.95
0.25
0.36
0.13
0.18
2.95
3.05
0.65 BSC
2.95
3.05
4.78
5.03
0.41
0.66
0∞
6∞
0.5250 BSC
TOP VIEW
A1
A2
A
α
c
e
b
L
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL
DOCUMENT CONTROL NO.
21-0036
REV.
J
1
1
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2004 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.