LM2902NS datasheet, PDF - EEWORLD Datasheet

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LM2902NS: DescriptionOperational Amplifier, 4 Func, BIPolar, PDIP14; CategoryAnalog mixed-signal IC Amplifier circuit; File Size548KB，11 Pages; ManufacturerMotorola ( NXP ); Websitehttps://www.nxp.com

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LM2902NS Overview

Operational Amplifier, 4 Func, BIPolar, PDIP14

LM2902NS Parametric

Parameter Name	Attribute value
Is it Rohs certified?	incompatible
Maker	Motorola ( NXP )
package instruction	DIP, DIP14,.3
Reach Compliance Code	unknow
Amplifier type	OPERATIONAL AMPLIFIER
Architecture	VOLTAGE-FEEDBACK
frequency compensation	YES
JESD-30 code	R-PDIP-T14
JESD-609 code	e0
low-dissonance	NO
micropower	YES
Number of functions	4
Number of terminals	14
Maximum operating temperature	85 °C
Minimum operating temperature	-40 °C
Package body material	PLASTIC/EPOXY
encapsulated code	DIP
Encapsulate equivalent code	DIP14,.3
Package shape	RECTANGULAR
Package form	IN-LINE
power supply	5/26 V
Certification status	Not Qualified
surface mount	NO
technology	BIPOLAR
Temperature level	INDUSTRIAL
Terminal surface	Tin/Lead (Sn/Pb)
Terminal form	THROUGH-HOLE
Terminal pitch	2.54 mm
Terminal location	DUAL

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Application Report

SLVA650 – April 2014

Design of a Low Cost, 45W Flasher with Short Circuit

Protection Using LM2902 (Quad Op-Amp) and CSD18534

Gitesh Bhagwat

ABSTRACT

This Application note presents the design of a low cost, flasher circuit with short circuit protection. The

design incorporates the entire recommended design feature set for two wheeler flashers and includes -

low/high voltage operation, half load frequency doubling, and short circuit protection.

A circuit simulation and reference schematic are also provided.

Topic

...........................................................................................................................

Page

Introduction

........................................................................................................

Flasher Specifications

..........................................................................................

Design Using LM2902 (Quad Op-Amp) and CSD18534

..............................................

Operation

............................................................................................................

Test Results

........................................................................................................

Conclusion

........................................................................................................

References

........................................................................................................

SLVA650 – April 2014

Submit Documentation Feedback

Design of a Low Cost, 45W Flasher with Short Circuit Protection Using

LM2902 (Quad Op-Amp) and CSD18534

www.ti.com

Operation

The design of the flasher can be divided into three main segments:

4.1

Ocillator

The Op-amp U2-A acts as an oscillator triggering transistor Q5. This in turn triggers MOSFET Q4. The

frequency of oscillation is set to about 85 c/m as required by the specifications.

4.2

Frequency Doubling Circuit

The Op-amps U2-C (Current Sensing Amplifier) and U2-D (Comparator) form a frequency doubling circuit.

U2-C senses the load current across resistor R12, and amplifies it by a factor of 6.

U2-D then compares this amplified voltage with a threshold set by resistors R17 and R23.

4.2.1

Full Load Operation

As long as the amplified sensed voltage is higher than the threshold level, output of the comparator is

driven high which keeps the transistor Q3 turned on. This transistor, when turned on, brings the capacitor

C2 into action by connecting it to ground.

Thus the effective capacitance seen by the U2-A oscillator is approximately a parallel combination of C2

and C3. It is for this combination that the oscillation frequency is set to 85c/m.

4.2.2

Half Load Operation

When the load is halved (failure of one of the bulbs), the sensed and amplified voltage provided by U2-C

falls below the threshold set for U2-D. The output of U2-D comparator goes low thereby turning off the

transistor Q3. This disconnects capacitor C2.

Now, the U2-A oscillator sees only C3 which is approximately half of the parallel combination of C2 and

C3. This results in doubling of the oscillation frequency.

4.3

Short Circuit Protection

The U2-B is another comparator which is used for implementing short circuit protection.

When the output of U2-C exceeds the threshold set by R9 and R15, the output of U2-B goes high. The

transistor Q2 latches this high output. The diode D1 provides a unidirectional path for this high output to

latch Q6 which in turn latches off MOSFET Q4. This latching action is reversed only by resetting the circuit

(disconnecting V

Capacitor C5 connected on the positive terminal of U2-B, introduces a delay in the triggering of U2-B. This

is used to avoid false triggering due to high inrush current during cold start.

Figure 2

shows the worst case

cold start condition with 12.8V battery voltage. The circuit starts up within 1 second and avoids false

detection of the initial current spike as a short circuit. The capacitor C5 takes care of the same.

The start up time is measured to be 658 ms.

SLVA650 – April 2014

Submit Documentation Feedback

Design of a Low Cost, 45W Flasher with Short Circuit Protection Using

LM2902 (Quad Op-Amp) and CSD18534

LM2902NS Related Products

	LM2902NS
Description	Operational Amplifier, 4 Func, BIPolar, PDIP14
Is it Rohs certified?	incompatible
Maker	Motorola ( NXP )
package instruction	DIP, DIP14,.3
Reach Compliance Code	unknow
Amplifier type	OPERATIONAL AMPLIFIER
Architecture	VOLTAGE-FEEDBACK
frequency compensation	YES
JESD-30 code	R-PDIP-T14
JESD-609 code	e0
low-dissonance	NO
micropower	YES
Number of functions	4
Number of terminals	14
Maximum operating temperature	85 °C
Minimum operating temperature	-40 °C
Package body material	PLASTIC/EPOXY
encapsulated code	DIP
Encapsulate equivalent code	DIP14,.3
Package shape	RECTANGULAR
Package form	IN-LINE
power supply	5/26 V
Certification status	Not Qualified
surface mount	NO
technology	BIPOLAR
Temperature level	INDUSTRIAL
Terminal surface	Tin/Lead (Sn/Pb)
Terminal form	THROUGH-HOLE
Terminal pitch	2.54 mm
Terminal location	DUAL

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