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ICM7555/ICM7556
General-Purpose Timers
General Description
The Maxim ICM7555 and ICM7556 are respectively single and dual general-purpose RC timers capable of generating accurate time delays or frequencies. The primary
feature is an extremely low supply current, making this
device ideal for battery-powered systems. Additional features include low THRESHOLD, TRIGGER, and RESET
currents, a wide operating supply voltage range, and
improved performance at high frequencies.
These CMOS low-power devices offer significant performance advantages over the standard 555 and 556 bipolar
timers. Low-power consumption, combined with the virtually
nonexistent current spike during output transitions, make
these timers the optimal solution in many applications.
Applications
● Pulse Generator
● Precision Timing
● Time Delay Generation
● Pulse-Width Modulation
● Pulse Position Modulation
● Sequential Timing
● Missing Pulse Detector
Features
● Improved 2nd Source (See 4th Page for Maxim
Advantage)
● Wide Supply Voltage Range: 2V to 18V
● No Crowbarring of Supply During Output Transition
● Adjustable Duty Cycle
● Low THRESHOLD, TRIGGER, and RESET Currents
● TTL Compatible
● Monolithic, Low-Power CMOS Design
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
ICM7555ESA
-40°C to +85°C
8 SO
ICM7555IPA
-20°C to +85°C
8 PDIP
ICM7555ISA
-20°C to +85°C
8 SO
ICM7555MJA/HR
-55°C to +125°C
8 CERDIP
ICM7555/D
Pin Configurations
0°C to +70°C
Dice
ICM7556IPD
-20°C to +85°C
14 PDIP
ICM7556ISD
-20°C to +85°C
14 SO
ICM7556MJD
-55°C to +125°C
14 CERDIP
ICM7556/D
0°C to +70°C
Dice
Typical Operating Circuit
19-0481; Rev 3; 3/13
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ICM7555/ICM7556
General-Purpose Timers
Absolute Maximum Ratings (Note 1)
Supply Voltage ....................................................................+18V
Input Voltage TRIGGER
Control Voltage THRESHOLD...............< V+ +0.3V to ≥ -0.3V
RESET
Output Current...................................................................100mA
Power Dissipation (Note 2)
ICM7556.......................................................................300mW
ICM7555.......................................................................200mW
Operating Temperature Range
ICM75551JA (Maxim)...................................... -20°C to +85°C
ICM75551SA (Maxim) .................................... -20°C to +85°C
ICM75551PA.................................................... -20°C to +85°C
ICM75551TV................................................... -20°C to +85°C
ICM75561PD................................................... -20°C to +85°C
ICM7555MTV................................................ -55°C to +125°C
ICM7556MJD................................................. -55°C to +125°C
Storage Temperature......................................... -65°C to +150°C
Lead Temperature (soldering, 60s).................................. +300°C
Note 1: Due to the SCR structure inherent in the CMOS process used to fabricate these devices, connecting any terminal to a voltage greater than V+ + 0.3V or less than V- - 0.3V may cause destructive latchup. For this reason it is recommended that no
inputs from external sources not operating from the same power supply be applied to the device before its power supply is
established in multiple systems. The supply of the ICM7555/ICM7556 must be turned on first.
Note 2: Junction temperatures should not exceed 135°C and the power dissipation must be limited to 20mW at +125°C. Below
125°C, power dissipation may be increased to 300mW at 25°C. Derating factor is approximately 3mW/°C (ICM7556) or
2mW/°C (ICM7555).
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
(V+ = +2V to +15V; TA = +25°C, unless otherwise noted.)
PARAMETER
Supply Voltage
SYMBOL
V+
CONDITIONS
2
18
3
16
I+
Timing Error
RA, RB = 1kΩ to
100kΩ, C = 0.1µF
Initial Accuracy
(Note 4)
Drift with Temperature
(Note 4)
Drift with Supply Voltage
V+ = 5V
Trigger Voltage
Trigger Current
Threshold Current
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MAX
-55°C ≤ TA ≤ +125°
ICM7556
Threshold Voltage
TYP
-20°C ≤ TA ≤ +70°
ICM7555
Supply Current (Note 3)
MIN
V+ = 2V
60
200
V+ = 18V
120
300
V+ = 2V
120
400
V+ = 18V
240
600
2.0
5.0
UNITS
V
µA
5V ≤ V+ ≤ 15V
V+ = 5V
50
V+ = 10V
75
V+ = 15V
100
%
ppm/°C
1.0
3.0
%/V
VTH
V+ = 5V
0.63
0.66
0.67
V+
VTRIG
V+ = 5V
0.29
0.33
0.34
V+
ITRIG
ITH
V+ = 18V
50
V+ = 5V
10
V+ = 2V
1
V+ = 18V
50
V+ = 5V
10
V+ = 2V
1
pA
pA
Analog Devices │ 2
ICM7555/ICM7556
General-Purpose Timers
Electrical Characteristics (continued)
(V+ = +2V to +15V; TA = +25°C, unless otherwise noted.)
PARAMETER
Reset Current
SYMBOL
IRST
Reset Voltage
VRST
Control Voltage Lead
VCV
CONDITIONS
VREST = Ground
TYP
V+ = 18V
100
V+ = 5V
20
V+ = 2V
2
MAX
0.4
0.7
1.0
V+ = 2V
0.4
0.7
1.0
V+ = 5V
0.62
0.66
0.67
VO
Output Hi
V+ = 18V
ISINK = 3.2mA
0.1
0.4
V+ = 5V
ISINK = 3.2mA
0.15
0.4
V+ = 18V
ISOURCE = 1.0mA
17.25
17.8
V+ = 5V
ISOURCE = 1.0mA
4.0
4.5
Rise Time of Output
tr
RL = 10MΩ
CL = 10pF V+ = 5V
35
40
75
Fall Time of Output
tf
RL = 10MΩ
CL = 10pF V+ = 5V
35
40
75
Guaranteed Max Osc.
Frequency
fmax
Astable operation
UNITS
pA
V+ = 18V
Output Lo
Output Voltage Drop
MIN
500
V
V
V
ns
kHz
Note 3: The supply current value is essentially independent of the TRIGGER, THRESHOLD, and RESET voltages.
Note 4: Parameter is not 100% tested. Majority of all units meet this specification.
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Analog Devices │ 3
ICM7555/ICM7556
General-Purpose Timers
Maxim Advantage
● Lower Supply Current
● Increased Output Source Current
● Guaranteed THRESHOLD, TRIGGER, and RESET
Input Currents
● Guaranteed Discharge Output Voltage
● Supply Current Guaranteed Over Temperature
● Significantly Improved ESD Protection (Note 6)
● Maxim Quality and Reliability
Absolute Maximum Ratings
This device conforms to the Absolute Maximum Ratings on adjacent page.
Electrical Characteristics
Specifications below satisfy or exceed all “tested” parameters on adjacent page.
(V+ = +2V to +15V; TA = +25°C, unless otherwise noted.)
PARAMETER
Supply Voltage
SYMBOL
V+
CONDITIONS
MIN
16.5
-55°C ≤ TA ≤ +125°
3
16
ICM7555
I+
30
120
V+ = 5V; -20°C ≤ TA ≤ +85°C
250
V+ = 5V; -55°C ≤ TA ≤ +125°C
300
60
240
V+ = 5V; -20°C ≤ TA ≤ +85°C
500
V+ = 5V; -55°C ≤ TA ≤ +125°C
600
2.0
Drift with Temperature
Drift with Supply Voltage
Threshold Current
Reset Current
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µA
500
V+ = 5V; TA = +25°C
Initial Accuracy (Note 5)
Trigger Current
V
µA
Circuit of Figure 1b;
RA = RB 100kΩ, C = 0.1µF, V+ = 5V
Timing Error (Note 4)
Trigger Voltage
UNITS
250
V+ = 5V; TA = +25°C
V+ = 2V to 16.5V; TA = +25°C
ICM7556
Threshold Voltage
MAX
2
V+ = 2V to 16.5V; TA = +25°C
Supply Current
(Note 3)
TYP
-20°C ≤ TA ≤ +85°
5.0
%
V+ = 5V
50
V+ = 10V
75
V+ = 15V
100
V+ = 5V
1.0
3.0
%V
ppm/°C
VTH
V+ = 5V
0.63
0.66
0.67
V+
VTRIG
V+ = 5V
0.29
0.33
0.34
V+
ITRIG
ITH
IRST
V+ = 16.5V
50
V+ = 5V
10
V+ = 2V
1
V+ = 16.5V
50
V+ = 5V
10
V+ = 2V
1
VREST = Ground
V+ = 16.5V
100
V+ = 5V
20
V+ = 2V
2
pA
pA
pA
Analog Devices │ 4
ICM7555/ICM7556
General-Purpose Timers
Electrical Characteristics (continued)
Specifications below satisfy or exceed all “tested” parameters on adjacent page.
(V+ = +2V to +15V; TA = +25°C, unless otherwise noted.)
PARAMETER
SYMBOL
Reset Voltage
VRST
Control Voltage
VCV
CONDITIONS
MIN
TYP
MAX
V+ = 16.5V
0.4
0.7
1.2
V+ = 2V
0.4
0.7
1.2
V+ = 5V
0.62
0.66
0.67
Output Lo
Output Voltage Drop
VO
Output Hi
Discharge Output Voltage
VDIS
V+ = 16.5V
ISINK = 3.2mA
0.1
0.4
V+ = 5V
ISINK = 3.2mA
0.15
0.4
V+ = 16.5V
ISOURCE = 2.0mA
15.75
16.25
V+ = 5V
ISOURCE = 2.0mA
4.0
4.5
V+ = 5V, IDIS = 3.2mA
Rise Time of Output
(Note 4)
tr
RL = 10MΩ
CL = 10pF
V+ = 5V
Fall Time of Output
(Note 4)
tf
RL = 10MΩ
CL = 10pF
V+ = 5V
Guaranteed Max Osc.
Frequency (Note 4)
fmax
Astable Operation
35
0.1
0.4
40
75
UNITS
V
V+
V
V
ns
35
500
40
75
kHz
Note 1: Due to tho SCR structure inherent in the CMOS process used to fabricate these devices, connecting any terminal to a voltage greater than V+ + 3V or less than V- - 0.3V may cause destructive latchup. For this reason it is recommended that no
inputs from external sources not operating from the same power supply be applied to the device before its power supply is
established. In multiple systems, the supply of the ICM7555/ICM7556 must be turned on first.
Note 2: Junction temperatures should not exceed 135°C and the power dissipation must be limited to 20mW at 125°C. Below
125°C, power dissipation may be increased to 300mW at 25°C. Derating factor is approximately 3mW/°C (ICM7556) or
2mW/°C (ICM7555).
Note 3: The supply current value is essentially independent of the TRIGGER, THRESHOLD, and RESET voltages.
Note 4: Parameter is not 100% tested. Majority of all units meet this specification.
Note 5: Deviation from f = 1.46/(RA + 2 RB)C. V+ = 5V.
Note 6: All pins are designed to withstand electrostatic discharge (ESD) level in excess of 2000V. (Mil Std 883B Method 3015 1
Test Circuit).
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Analog Devices │ 5
ICM7555/ICM7556
General-Purpose Timers
Typical Operating Characteristics
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Analog Devices │ 6
ICM7555/ICM7556
General-Purpose Timers
Typical Operating Characteristics (continued)
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Analog Devices │ 7
ICM7555/ICM7556
General-Purpose Timers
Detailed Description
Both the ICM7555 timer and the ICM7556 dual timer can
be configured for either astable or monostable operation.
In the astable mode, the free-running frequency and the
duty cycle are controlled by two external resistors and
one capacitor. Similarly, the pulse width in the monostable
mode is precisely controlled by one external resistor and
capacitor.
The external component count is decreased when replacing a bipolar timer with the ICM7555 or ICM7556. The
bipolar devices produce large crowbar currents in the
output driver. To compensate for this spike, a capacitor
is used to decouple the power-supply lines. The CMOS
timers produce supply spikes of only 2mA to 3mA vs.
300mA to 400mA (Bipolar), therefore supply decoupling
is typically not needed. This current spike comparison is
illustrated in Figure 3. Another component is eliminated at
the control voltage pin. These CMOS timers, due to the
high-impedance inputs of the comparators, do not require
decoupling capacitors on the control voltage pin.
Figure 3. Supply Current Transient Compared With A Standard
Bipolar 555 During An Output Transition
Applications Information
Astable Operation
Maxim recommends either of the two astable circuit configurations illustrated in Figure 1. The circuit in Figure 1a
provides a 50% duty-cycle output using one timing resistor
and capacitor. The oscillator waveform across the capacitor is symmetrical and triangular, swinging from 1/3 to 2/3
of the supply voltage. The frequency generated is defined
by:
f=
1
1.4 RC
The circuit in Figure 1b provides a means of varying the
duty cycle of the oscillator. The frequency is defined by:
f=
1.46
(R A + 2R B ) C
The duty cycle is:
Figure 1. Maxim ICM7555 Used in Two Different Astable
Configurations
D=
RB
(R A + 2R B )
Monostable Operation
The circuit diagram in Figure 2 illustrates monostable
operation. In this mode the timer acts as a one shot.
Initially the external capacitor is held discharged by
the discharge output. Upon application of a negative
TRIGGER pulse to pin 2, the capacitor begins to charge
exponentially through RA. The device resets after the voltage across the capacitor reaches ⅔(V+).
Figure 2. Maxim ICM7555 in Monostable Operation
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tOUTPUT = -In(1/3)RAC = 1.1RAC
Analog Devices │ 8
ICM7555/ICM7556
General-Purpose Timers
Reset
The reset function is significantly improved over the
standard bipolar 555 and 556 in that it controls only the
internal flip-flop, which in turn simultaneously controls the
state of the Output and Discharge pins. This avoids the
multiple threshold problems sometimes encountered with
slow-falling edges of the bipolar devices. This input is
designed to have essentially the same trip voltage as the
standard bipolar devices (0.6V to 0.7V). At all supply voltages this input maintains an extremely high impedance.
Control Voltage
The control voltage regulates the two trip voltages for the
THRESHOLD and TRIGGER internal comparators. This
pin can be used for frequency modulation in the astable
mode. By varying the applied voltage to the control voltage
pin, delay times can be changed in the monostable mode.
Power-Supply Considerations
Since the TRIGGER, THRESHOLD, and Discharge
leakage currents are very low, high-impedance timing
components may be used, keeping total system supply
current at a minimum.
Output Drive Capability
The CMOS output stage is capable of driving most logic
families including CMOS and TTL. The ICM7555 and
ICM7556 will drive at least two standard TTL loads at a
supply voltage of 4.5V or greater. When driving CMOS,
the output swing at all supply voltage levels will equal the
supply voltage.
Figure 5. Equivalent Circuit
Function Table
RESET
TRIGGER THRESHOLD
VOLTAGE
VOLTAGE
OUTPUT
DISCHARGE
SWITCH
Low
Irrelevant
Irrelevant
Low
On
High
< 1/3 V+
Irrelevant
High
Off
High
> 1/3 V+
> 2/3 V+
Low
On
< 2/3 V+
As previously established
High
†Voltage
> 1/3 V+
levels shown are nominal.
Note: RESET will dominate all other inputs. TRIGGER will
dominate over THRESHOLD.
Figure 4. Block Diagram of ICM7555
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Analog Devices │ 9
ICM7555/ICM7556
Chip Information
PROCESS: CMOS
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General-Purpose Timers
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
8 PDIP
P8-1
21-0043
—
8 SO
S8-2
21-0041
90-0096
14 PDIP
P14-3
21-0043
—
14 CERDIP
J14-3
21-0045
—
14 SO
S14-1
21-0041
90-0112
Analog Devices │ 10
ICM7555/ICM7556
General-Purpose Timers
Revision History
REVISION
NUMBER
REVISION
DATE
0
4/88
Initial Release
—
2
11/92
Revised Electrical Characteristics
3
3
3/13
Updated Ordering Information
1
DESCRIPTION
PAGES
CHANGED
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is
assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that
may result from its use.Specifications subject to change without notice. No license is granted by implicationor
otherwise under any patent or patent rights of Analog Devices. Trademarks andregistered trademarks are the
property of their respective owners.
w w w . a n a l o g . c o m
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