LM3905N National Semiconductor, LM3905N Datasheet

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LM3905N

Manufacturer Part Number
LM3905N
Description
IC TIMER PRECISION 8-DIP
Manufacturer
National Semiconductor
Datasheet

Specifications of LM3905N

Voltage - Supply
*
Current - Supply
2.5mA
Operating Temperature
*
Package / Case
*
Frequency
*
Count
*
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Other names
*LM3905N
LM3905

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C 1995 National Semiconductor Corporation
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
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 V
achieved
Connection Diagrams
See NS Package Number H10C
Order Number LM122H
Metal Can Package
ADJ
Top View
pin Timing ratios of 50 1 can be easily
g
TL H 7768– 6
TL H 7768
40V even when using a 5V
See NS Package Number N14A
Dual-In-Line Package
Order Number LM322N
Top View
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 s to multi-hour timing range with excellent repeat-
ability
The LM122 operates over a temperature range of
0 C to
except that the boost and V
able limiting minimum timing period to 1 ms
Features
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
a
125 C An electrically identical LM322 is specified from
Immune to changes in trigger voltage during timing
interval
Timing periods from microseconds to hours
Internal logic reversal
Immune to power supply ripple during the timing
interval
Operates from 4 5V to 40V supplies
Input protected to
Floating transistor output with internal current limiting
Internal regulated reference
Timing period can be voltage controlled
TTL compatible input and output
a
TL H 7768 – 7
70 C The LM3905 is identical to the LM122 series
g
40V
See NS Package Number N08E
Order Number LM3905N
Dual-In-Line Package
ADJ
pin options are not avail-
Top View
RRD-B30M115 Printed in U S A
February 1995
TL H 7768 – 8
b
55 C to

Related parts for LM3905N

LM3905N Summary of contents

Page 1

... TTL compatible input and output Y Dual-In-Line Package TL H 7768 – 7 See NS Package Number N08E Top View Order Number LM322N See NS Package Number N14A February 1995 pin options are not avail- ADJ Dual-In-Line Package TL H 7768 – 8 Top View Order Number LM3905N RRD-B30M115 Printed ...

Page 2

... Absolute Maximum Ratings If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Power Dissipation a V Voltage Collector Output Voltage V Current REF Trigger Voltage V Voltage (Forced) ADJ Electrical Characteristics Parameter Conditions Timing Ratio ...

Page 3

Typical Performance Characteristics Comparator Bias Current Supply Current Output Transistor Saturation Characteristics at Low Currents Reference Regulation Short Output Pulse (LM122 LM322) Comparator Bias Current Comparator Bias Current (LM122 LM322) Trigger Input Characteristics Trigger Threshold Collector Output Saturation Timing Error ...

Page 4

Schematic Diagram 4 ...

Page 5

Functional Diagram Timing Diagram 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 ...

Page 6

Pin Function Description (Continued) trollers Typical temperature drift of the reference is less than 0 01% C The trigger terminal is used to start a timing cycle (see functional diagram) Initially Q1 is saturated C charged and the latching buffer ...

Page 7

Pin Function Description (Continued) for instance cannot be held for more than 4 seconds These levels are based maximum initial chip tem- perature When driving inductive loads always use a clamp diode to protect the transistor from ...

Page 8

Typical Applications (Continued) FIGURE 4 Time Out on Power Up (Relay Energized Until R C Seconds After V is Applied FIGURE 5 5V Logic Supply Driving 28V Relay 30V Supply Interfacing with 5V Logic Figure 6 indicates ...

Page 9

Typical Applications (Continued) The average charging current through R is about some attention must be paid to parts layout to prevent stray leakage paths The suggested timing capacitor has a typical self time constant of 300 ...

Page 10

Typical Applications (Continued) In this application the logic terminal is normally held high by R3 When a trigger pulse is received Q1 is turned on driv- ing the logic terminal to ground The result of triggering the timer and reversing ...

Page 11

Application Hints (Continued) Timer Protected Against Damage for up to 50V FIGURE 15 Comparator with Threshold Eliminating Timing Cycle Upon Initial Application of Power The LM122 will normally start a timing cycle (with no trigger input) when ...

Page 12

Application Hints (Continued) Triggering with Negative Edge Although the LM122 is triggered by a positive going trigger signal a differentiator tied to a normally ‘‘high’’ trigger will result in negative edge triggering In Figure 19 R1 serves the dual purpose ...

Page 13

Physical Dimensions inches (millimeters) Metal Can Package (H) Order Number LM122H NS Package Number H10C Dual-In-Line Package (N) Order Number LM322N NS Package Number N14A 13 ...

Page 14

... National does not assume any responsibility for use of any circuitry described no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications Dual-In-Line Package (N) Order Number LM3905N NS Package Number N08E 2 A critical component is any component of a life ...

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