LP395
LP395 Ultra Reliable Power Transistor
Literature Number: SNOSBF3B
LP395
Ultra Reliable Power Transistor
General Description
The LP395 is a fast monolithic transistor with complete
overload protection. This very high gain transistor has in-
cluded on the chip, current limiting, power limiting, and ther-
mal overload protection, making it difficult to destroy from
almost any type of overload. Available in an epoxy TO-92
transistor package this device is guaranteed to deliver 100
mA.
Thermal limiting at the chip level, a feature not available in
discrete designs, provides comprehensive protection against
overload. Excessive power dissipation or inadequate heat
sinking causes the thermal limiting circuitry to turn off the
device preventing excessive die temperature.
The LP395 offers a significant increase in reliability while
simplifying protection circuitry. It is especially attractive as a
small incandescent lamp or solenoid driver because of its
low drive requirements and blowout-proof design.
The LP395 is easy to use and only a few precautions need
be observed. Excessive collector to emitter voltage can de-
stroy the LP395 as with any transistor. When the device is
used as an emitter follower with a low source impedance, it
is necessary to insert a 4.7 kΩresistor in series with the
base lead to prevent possible emitter follower oscillations.
Also since it has good high frequency response, supply
by-passing is recommended.
Areas where the LP395 differs from a standard NPN transis-
tor are in saturation voltage, leakage (quiescent) current and
in base current. Since the internal protection circuitry re-
quires voltage and current to function, the minimum voltage
across the device in the on condition (saturated) is typically
1.6 Volts, while in the off condition the quiescent (leakage)
current is typically 200 µA. Base current in this device flows
out of the base lead, rather than into the base as is the case
with conventional NPN transistors. Also the base can be
driven positive up to 36 Volts without damage, but will draw
current if driven negative more than 0.6 Volts. Additionally, if
the base lead is left open, the LP395 will turn on.
The LP395 is a low-power version of the 1-Amp LM195/
LM295/LM395 Ultra Reliable Power Transistor.
The LP395 is rated for operation over a −40˚C to +125˚C
range.
Features
nInternal thermal limiting
nInternal current and power limiting
nGuaranteed 100 mA output current
n0.5 µA typical base current
nDirectly interfaces with TTL or CMOS
n+36 Volts on base causes no damage
n2 µs switching time
Connection Diagram
TO-92 Package
00552501
Order Number LP395Z
See NS Package Z03A
Typical Applications
Fully Protected Lamp Driver
00552503
April 2005
LP395 Ultra Reliable Power Transistor
© 2005 National Semiconductor Corporation DS005525 www.national.com
Absolute Maximum Ratings (Note 1)
Collector to Emitter Voltage 36V
Collector to Base Voltage 36V
Base to Emitter Voltage (Forward) 36V
Base to Emitter Voltage (Reverse) 10V
Base to Emitter Current (Reverse) 20 mA
Collector Current Limit Internally Limited
Power Dissipation Internally Limited
Operating Temperature Range −40˚C to +125˚C
Storage Temperature Range −65˚C to +150˚C
Lead Temp. (Soldering, 10 seconds) 260˚C
Electrical Characteristics
Tested Design Units
Symbol Parameter Conditions Typical Limit Limit (Limit)
(Note 3) (Note 4)
V
CE
Collector to Emitter 0.5 mA ≤I
C
≤100 mA 36 36 V(Max)
Operating Voltage (Note 2)
I
CL
Collector Current Limit V
BE
= 2V, V
CE
= 36V 45 25 20 mA(Min)
(Note 5) V
BE
= 2V, V
CE
= 15V 90 60 50 mA(Min)
V
BE
= 2V, 2V ≤V
CE
≤6V 130 100 100 mA(Min)
I
B
Base Current 0 ≤I
C
≤100 mA −0.3 −2.0 −2.5 µA(Max)
I
Q
Quiescent Current V
BE
=0V,0≤V
CE
≤36V 0.24 0.50 0.60 mA(Max)
V
CE(SAT)
Saturation Voltage V
BE
= 2V, I
C
= 100 mA 1.82 2.00 2.10 V(Max)
BV
BE
Base to Emitter Break- 0 ≤V
CE
≤36V, I
B
=2µA 36 36 V(Min)
down Voltage (Note 5)
V
BE
Base to Emitter Voltage I
C
= 5 mA 0.69 0.79 0.90 V(Max)
(Note 6) I
C
= 100 mA (Note 5) 1.02 1.40 V (Max)
t
S
Switching Time V
CE
= 20V, R
L
= 200Ω2µs
V
BE
= 0V, +2V, 0V
θ
JA
Thermal Resistance 0.4" leads soldered to 150 180 ˚C/W
Junction to Ambient printed circuit board (Max)
0.125" leads soldered to 130 160 ˚C/W
printed circuit board (Max)
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits.
Note 2: Parameters identified with boldface type apply at temp. extremes. All other numbers, unless noted apply at +25˚C.
Note 3: Guaranteed and 100% production tested.
Note 4: Guaranteed (but not 100% production tested) over the operating temperature and supply voltage ranges. These limits are not used to calculate outgoing
quality levels.
Note 5: These numbers apply for pulse testing with a low duty cycle.
Note 6: Base positive with respect to emitter.
Simplified Circuit
00552505
LP395
www.national.com 2
Applications Information
One failure mode incandescent lamps may experience is
one in which the filament resistance drops to a very low
value before it actually blows out. This is especially rough on
most solid-state lamp drivers and in most cases a lamp
failure of this type will also cause the lamp driver to fail.
Because of its high gain and blowout-proof design, the
LP395 is an ideal candidate for reliably driving small incan-
descent lamps. Additionally, the current limiting characteris-
tics of the LP395 are advantageous as it serves to limit the
cold filament inrush current, thus increasing lamp life.
Typical Performance Characteristics
5 Volt Transfer Function 36 Volt Transfer Function
00552510 00552511
Collector Characteristics Available Collector Current
00552512 00552513
Quiescent Collector Current Saturation Voltage
00552514 00552515
LP395
www.national.com3
Typical Performance Characteristics (Continued)
Collector Current Threshold
00552509
Typical Applications
Lamp Flasher
(Short Circuit Proof)
Optically Isolated
Switch
00552506 00552507
Two Terminal
Current Limiter Composite PNP
00552508 00552502
LP395
www.national.com 4
Physical Dimensions inches (millimeters) unless otherwise noted
Order Number LP395Z
NS Package Z03A
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.
For the most current product information visit us at www.national.com.
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LP395 Ultra Reliable Power Transistor
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