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National Semiconductor Electronic Components Datasheet

LM3905 Datasheet

Precision Timers

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February 1995
LM122 LM322 LM3905 Precision Timers
General Description
The LM122 series are precision timers that offer great ver-
satility 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 reg-
ulator circuits complement the basic timing function
enabling the LM122 series to operate in many different ap-
plications 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 driv-
ing and signal conditioning where an open collector or emit-
ter 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 g40V even 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 con-
venient 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 VADJ pin Timing ratios of 50 1 can be easily
achieved
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 repeat-
ability
The LM122 operates over a temperature range of b55 C to
a125 C An electrically identical LM322 is specified from
0 C to a70 C The LM3905 is identical to the LM122 series
except that the boost and VADJ pin options are not avail-
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 to g40V
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
Connection Diagrams
Metal Can Package
Dual-In-Line Package
Dual-In-Line Package
TL H 7768–6
Top View
Order Number LM122H
See NS Package Number H10C
TL H 7768 – 7
Top View
Order Number LM322N
See NS Package Number N14A
TL H 7768 – 8
Top View
Order Number LM3905N
See NS Package Number N08E
C1995 National Semiconductor Corporation TL H 7768
RRD-B30M115 Printed in U S A


National Semiconductor Electronic Components Datasheet

LM3905 Datasheet

Precision Timers

No Preview Available !

Absolute Maximum Ratings
If Military Aerospace specified devices are required
please contact the National Semiconductor Sales
Office Distributors for availability and specifications
Power Dissipation
Va Voltage
500 mW
40V
Collector Output Voltage
40V
VREF Current
Trigger Voltage
5 mA
g40V
VADJ Voltage (Forced)
5V
Logic Reverse Voltage
5 5V
Output Short Circuit Duration (Note 1)
Lead Temperature
(Soldering 10 sec )
260 C
Operating Temperature Range
LM122
LM322
LM3905
b55 C s TA s a125 C
0 C s TA s a70 C
0 C s TA s a70 C
Electrical Characteristics (Note 2)
Parameter
Conditions
LM122
LM322
LM3905
Units
Min Typ Max Min Typ Max Min Typ Max
Timing Ratio
TA e 25 C 4 5V s Va s 40V 0 626 0 632 0 638 0 620 0 632 0 644 0 620 0 632 0 644
Boost Tied to Va (Note 3)
0 620 0 632 0 644 0 620 0 632 0 644
Comparator Input
Current
TA e 25 C 4 5V s Va s 40V
Boost Tied to Va
03 10
30 100
03 15
30 100
0 5 1 5 nA
nA
Trigger Voltage
Trigger Current
Supply Current
Timing Ratio
TA e 25 C 4 5V s Va s 40V
TA e 25 C VTRIG e 2V
TA t 25 C 4 5V s Va s 40V
4 5V s Va s 40V
Boost Tied to Va
12
0 62
0 62
16 2 12
25
25 4
0 644 0 61
0 644 0 61
16 2 12
25
25 45
0 654 0 61
0 654
16 2
V
25 mA
2 5 4 5 mA
0 654
Comparator Input
Current
4 5V s Va s 40V
Boost Tied to Va (Note 4)
b5
5 b2
100
2 b2 5
150
2 5 nA
nA
Trigger Voltage
4 5V s Va s 40V
08 25 08 25 08 25 V
Trigger Current
Output Leakage
Current
VTRIG e 2 5V
VCE e 40V
200 200 200 mA
1 5 5 mA
Capacitor Saturation
Voltage
Reset Resistance
Rt t 1 MX
Rt e 10 kX
2 5 2 5 2 5 mV
25 25 25 mV
150 150 150 X
Reference Voltage
Reference Regulation
TA e 25 C
0 s IOUT s 3 mA
4 5V s Va s 40V
3 3 15 3 3
20 50
6 25
3 3 15 3 3
20 50
6 25
3 3 15 3 3 V
20 50 mV
6 25 mV
Collector Saturation
Voltage
Emitter Saturation
Voltage
Average Temperature
Coefficient of Timing
Ratio
IL e 8 mA
IL e 50 mA
TA e 25 C IL e 3 mA
TA e 25 C IL e 50 mA
0 25 0 4
07 14
18 22
21 3
0 003
0 25 0 4
07 14
18 22
21 3
0 003
0 25 0 4
07 14
18 22
21 3
V
V
V
V
0 003
%C
Minimum Trigger Width VTRIG e 3V
0 25 0 25 0 25 ms
Note 1 Continuous output shorts are not allowed Short circuit duration at ambient temperatures up to 40 C may be calculated from t e 120 VCE seconds where
VCE is the collector to emitter voltage across the output transistor during the short
Note 2 These specifications apply for TAMIN s TA s TAMAX unless otherwise noted
Note 3 Output pulse width can be calculated from the following equation t e (Rt) (Ct) 1 b 2(0 632 b r) b VC VREF) where r is timing ratio and VC is capacitor
saturation voltage This reduces to t e (Rt) (Ct) for all but the most critical applications
Note 4 Sign reversal may occur at high temperatures (l 100 C) where comparator input current is predominately leakage See typcial curves
Note 5 Refer to RETS122X drawing of military LM122H version for specifications
2


Part Number LM3905
Description Precision Timers
Maker National Semiconductor
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LM3905 Datasheet PDF






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