NSC LM122H, LM322N Datasheet
LM122/LM322/LM3905 Precision Timers
General Description
The LM122 series are precision timers that offer great versatility with high accuracy. They operate with unregulated
supplies from 4.5V to 40V while maintaining constant timing
periods from microseconds to hours. Internal logic and regulator circuits complement the basic timing function
enabling the LM122 series to operate in many different applications with a minimum of external components.
The output of the timer is a floating transistor with built in
current limiting. It can drive either ground referred or supply
referred loads up to 40V and 50 mA. The floating nature of
this output makes it ideal for interfacing, lamp or relay driving, and signal conditioning where an open collector or emitter is required. A ‘‘logic reverse’’ circuit can be programmed
by the user to make the output transistor either ‘‘on’’ or
‘‘off’’ during the timing period.
The trigger input to the LM122 series has a threshold of
1.6V independent of supply voltage, but it is fully protected
against inputs as high as
g
40VÐeven when using a 5V
supply. The circuitry reacts only to the rising edge of the
trigger signal, and is immune to any trigger voltage during
the timing periods.
An internal 3.15V regulator is included in the timer to reject
supply voltage changes and to provide the user with a convenient reference for applications other than a basic timer.
External loads up to 5 mA can be driven by the regulator. An
internal 2V divider between the reference and ground sets
the timing period to 1 RC. The timing period can be voltage
controlled by driving this divider with an external source
through the V
achieved.
pin. Timing ratios of 50:1 can be easily
ADJ
The comparator used in the LM122 utilizes high gain PNP
input transistors to achieve 300 pA typical input bias current
over a common mode range of 0V to 3V. A boost terminal
allows the user to increase comparator operating current for
timing periods less than 1 ms. This lets the timer operate
over a 3 ms to multi-hour timing range with excellent repeatability.
The LM122 operates over a temperature range of
a
125§C. An electrically identical LM322 is specified from
0
Ctoa70§C. The LM3905 is identical to the LM122 series
§
except that the boost and V
able, limiting minimum timing period to 1 ms.
Features
Y
Immune to changes in trigger voltage during timing
interval
Y
Timing periods from microseconds to hours
Y
Internal logic reversal
Y
Immune to power supply ripple during the timing
interval
Y
Operates from 4.5V to 40V supplies
Y
Input protected tog40V
Y
Floating transistor output with internal current limiting
Y
Internal regulated reference
Y
Timing period can be voltage controlled
Y
TTL compatible input and output
February 1995
pin options are not avail-
ADJ
b
55§Cto
LM122/LM322/LM3905 Precision Timers
Connection Diagrams
Metal Can Package
TL/H/7768– 6
Dual-In-Line Package
Top View
Order Number LM122H
See NS Package Number H10C
Top View
TL/H/7768– 7
Order Number LM322N
See NS Package Number N14A
C
1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.
TL/H/7768
Dual-In-Line Package
TL/H/7768– 8
Top View
Order Number LM3905N
See NS Package Number N08E
Absolute Maximum Ratings
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Power Dissipation 500 mW
a
V
Voltage 40V
Collector Output Voltage 40V
Current 5 mA
V
REF
Trigger Voltage
V
Voltage (Forced) 5V
ADJ
g
40V
Logic Reverse Voltage 5.5V
Output Short Circuit Duration (Note 1)
Lead Temperature
(Soldering, 10 sec.) 260
Operating Temperature Range
LM122
LM322 0
LM3905 0
b
55§CsT
CsT
§
CsT
§
s
a
125§C
A
s
a
70§C
A
s
a
70§C
A
§
Electrical Characteristics (Note 2)
Parameter Conditions
a
Timing Ratio T
Comparator Input T
Current Boost Tied to V
Trigger Voltage T
Trigger Current T
Supply Current T
Timing Ratio 4.5VsV
e
25§C, 4.5VsV
A
Boost Tied to V
e
25§C, 4.5VsV
A
e
25§C, 4.5VsV
A
e
25§C, V
A
t
25§C, 4.5VsV
A
a
s
Boost Tied to V
a
Comparator Input 4.5VsV
s
TRIG
s
a
a
40V 0.62 0.644 0.61 0.654 0.61 0.654
a
40V 0.626 0.632 0.638 0.620 0.632 0.644 0.620 0.632 0.644
, (Note 3) 0.620 0.632 0.644 0.620 0.632 0.644
a
s
40V 0.3 1.0 0.3 1.5 0.5 1.5 nA
a
s
40V 1.2 1.6 2 1.2 1.6 2 1.2 1.6 2 V
e
2V 25 25 25 mA
a
s
40V 2.5 4 2.5 4.5 2.5 4.5 mA
40V
Current Boost Tied to Va, (Note 4) 100 150 nA
a
Trigger Voltage 4.5VsV
Trigger Current V
Output Leakage V
Current
Capacitor Saturation R
Voltage R
TRIG
CE
t
t
s
40V 0.8 2.5 0.8 2.5 0.8 2.5 V
e
2.5V 200 200 200 mA
e
40V
t
1MX 2.5 2.5 2.5 mV
e
10 kX 25 25 25 mV
Reset Resistance 150 150 150 X
Reference Voltage T
Reference Regulation 0sI
Collector Saturation I
Voltage I
Emitter Saturation T
Voltage T
e
25§C 3 3.15 3.3 3 3.15 3.3 3 3.15 3.3 V
A
s
3mA 2050 2050 2050mV
OUT
a
s
4.5V
L
L
A
A
s
V
40V 6 25 6 25 6 25 mV
e
8 mA 0.25 0.4 0.25 0.4 0.25 0.4 V
e
50 mA 0.7 1.4 0.7 1.4 0.7 1.4 V
e
e
25§C, I
25§C, I
e
3 mA 1.8 2.2 1.8 2.2 1.8 2.2 V
L
e
50 mA 2.1 3 2.1 3 2.1 3 V
L
Average Temperature
Coefficient of Timing 0.003 0.003 0.003 %/
Ratio
Minimum Trigger Width V
Note 1: Continuous output shorts are not allowed. Short circuit duration at ambient temperatures up to 40§C may be calculated from te120/VCEseconds, where
is the collector to emitter voltage across the output transistor during the short.
V
CE
Note 2: These specifications apply for T
Note 3: Output pulse width can be calculated from the following equation: t
saturation voltage. This reduces to t
Note 4: Sign reversal may occur at high temperatures (
Note 5: Refer to RETS122X drawing of military LM122H version for specifications.
e
3V 0.25 0.25 0.25 ms
TRIG
s
s
T
T
AMIN
e
(Rt)(Ct) for all but the most critical applications.
unless otherwise noted.
A
AMAX
l
100§C) where comparator input current is predominately leakage. See typcial curves.
LM122 LM322 LM3905
Min Typ Max Min Typ Max Min Typ Max
30 100 30 100 nA
0.62 0.644 0.61 0.654
b
55
b
22
b
2.5 2.5 nA
155mA
e
(Rt)(Ct)[1b2(0.632br)bVC/V
) where r is timing ratio and VCis capacitor
REF
Units
C
C
§
2
Typical Performance Characteristics
Comparator Bias Current Comparator Bias Current (LM122/LM322)
Supply Current Trigger Input Characteristics Trigger Threshold
Comparator Bias Current
TL/H/7768– 3
Output Transistor Saturation
Characteristics at Low Currents
Reference Regulation Reference Regulation Suggested Timing Components
Short Output Pulse
(LM122/LM322)
Collector Output Saturation
Characteristics at High Current
Short Output Pulse
(LM122/LM322)
Timing Error Due to
Comparator Bias Current
Logic Pin Characteristics
TL/H/7768– 4
3
Schematic Diagram
TL/H/7768– 5
4
Functional Diagram
Timing Diagram
TL/H/7768– 9
Pin Function Description
One of the main features of the LM122 is its great versatility.
Since this device is unique, a description of the functions
and limitations of each pin is in order. This will make it much
easier to follow the discussion of the various applications
presented in this note.
a
V
is the positive supply terminal of the LM122. When using a single supply, this terminal may be driven by any voltage between 4.5V and 40V. The effect of supply variations
on timing period is less than 0.005%/V, so supplies with
high ripple content may be used without causing pulse width
changes. Supply bypassing on V
but may be necessary when driving highly reactive loads.
a
is not generally needed
Quiescent current drawn from the V
2.5 mA, independent of the supply voltage. Of course, additional current will be drawn if the reference is externally
loaded.
The V
enced to the ground pin. Up to 5.0 mA can be drawn from
this pin for driving external networks. In most applications
the timing resistor is tied to V
situations where a more linear charging current is required.
The regulated voltage is very useful in applications where
the LM122 is not used as a timer; such as switching regulators, variable reference comparators, and temperature con-
5
pin is the output of a 3.15V series regulator refer-
REF
a
terminal is typically
, but it need not be in
REF
TL/H/7768– 10
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