Datasheet L4945 Datasheet (SGS Thomson Microelectronics)



5V VERY LOW DROP VOLTAGE REGULATOR

5V ± 4%PRECISEOUTPUTVOLTAGE
OVER FULL TEMPERATURE RANGE
(– 40 / 125

VERY LOW VOLTAGE DROP (0.75Vmax)
OVER FULL TEMPERATURE RANGE

OUTPUTCURRENT UP TO 500mA
OVERVOLTAGE AND REVERSE VOLTAGE

PROTECTIONS
REVERSEVOLTAGEPROTECTION
SHORT CIRCUIT PROTECTION AND THER-

MAL SHUT-DOWN(with hysteresis)
LOW START UP CURRENT

DESCRIPTION

The L4945 is a monolithic integrated circuit in
Versawatt package specially designed to provide
a stabilized supply voltage for automotive and in­dustrial electronic systems. Thanks to their very
low voltage drop, in automotive applications the
devices can work correctly even during the crank-

C)

°

L4945

TO220

ORDERING NUMBER: L4945

ing phase, when the battery voltage could fall as
low as 6V. Furthermore, they incorporate a com­plete range of protection circuits against the dan­gerous overvoltages always present on the bat­tery rail of the car.

BLOCK DIAGRAM

This is advanced information on a new product now in development or undergoing evaluation.Details are subject tochange without notice.

March 1999

1/6

L4945

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

i

DC Input Voltage
DC Reverse Input Voltage
Transient Input Overvoltages :
Load Dump :

rise

≥ 0.5Ω

fall

=1µs, t

≤ 10ms

10ms, R

≤

= 500µs, R

fall

SOURCE

SOURCE

5ms ≤ t

Fall TimeConstant = 100ms

τ

f

R

SOURCE

Field Decay :
5ms≤t

Rise Time Constant = 33ms

τ

r

Low Energy Spike :
t

rise

Repetition Frequency = 5Hz

f

r

35

–18

80

–80

≥10Ω

±100

≥ 10Ω

V
V
V

V

V

T

J

T

OP

T

stg

Note: The circuitis ESD protectedaccording to MIL-STD-883C.

Junction Temperature Range – 40 to 150 °C
Operating Temperature Range – 40 to 125
Storage Temperature Range – 55 to 150 °C

PIN CONNECTION (Top view)

C

°

THERMAL DATA

Symbol Parameter Value Unit

Thermal Resistance Junction-case Max 3 °C/W

2/6

R

th j-case

TEST CIRCUIT

L4945

ELECTRICAL CHARACTERISTICS (refer to the test circuit, V

R

=1KΩ,RL=1KΩ, –40°C ≤ TJ≤ 125°C, unlessotherwise specified)

p

Symbol Parameter Test Conditions Min. Typ. Max. Unit

V

o

V

V

∆

∆V

V

i–Vo

I

q

V

∆

T

SVR Supply Volt.Rej. I

I

sc

Output Voltage Io= 0mA to 500mA

Operating Input Voltage Io= 0mA to (*) 500mA 6 26 V

i

Line Regulation Vi= 6V to 26V ;

o

Load Regulation Io= 5mA to 500mA 15 60 mV

o

Dropout Voltage Io= 500mA, TJ=25°C

Quiescent Current Io= 0mA, TJ=25°C

o

Temperature Output Voltage
Drift

Output Short Circuit Current 0.50 0.80 1.50 A

Over Full T Range

=25°C 4.90 5.00 5.10 V

T

j

I

= 5mA

o

Over Full T Range

I

= 0mA Over Full T

o

I

= 500mA Over Full T

o

= 350mA ; f = 120Hz

o

C

= 100µF;

o

V

= 12V±5V

i

pp

= 14.4V, Co=47µF, ESR < 10Ω,

i

4.80 5.00 5.20 V

210mV

0.40 0.55

6.5

110

– 0.5 mV/°C

50 60 dB

0.75

5

10
13

180

V
V

mA
mA
mA

(*) For a DC voltage 26 < Vi< 37V the device is not operating

FUNCTIONAL DESCRIPTION

The block diagram shows the basic structure of
the devices: the reference,the error amplifier,the
driver, the power PNP, the protection and reset
functions.

The power stage is a Lateral PNP transistor
which allows a very low dropout voltage (typ.
400mV at T
temperature range @ I

=25°C, max. 750mV over the full

J

= 500mA). The typical

O

curve of the dropout voltage as a function of the
junction temperature is shown in Fig. 1 : that is
the worst case, where I

= 500mA.

O

The current consumption of the devices (quies­cent current) are maximum 10mA - over full T -

when no load current is required.
The internal antisaturation circuit allows a drastic

reduction in the current peak which takes place
during the start up.

The three gain stages (operational amplifier,
driver and power PNP) require the external ca­pacitor (C

=20µF) to guarantee the global

omin

stabilityof the system.
Load dump and field decay protections(±80V,t =

300ms), reverse voltage (– 18V) and short circuit
protection, thermal shutdown are the main fea­tures that make the devices specially suitable for
applicationsin the automotive enviroment.

3/6

L4945

Figure 1:

TypicalDropout Voltage vs. T

j

(Io= 500mA).

EXTERNALCOMPENSATION
Since the purpose of a voltageregulatoris to sup-

ply and load variations, the open loop gain of the
regulators must be very high at low frequencies.
This may cause instability as a result of the vari-

ous poles present in the loop. To avoid this insta­bility dominant pole compensation is used to re­duce phase shift due to other poles at the unity
gain frequency. The lower the frequency of these
others poles at the unity gain frequency. The
lower the frequency of these other poles, the
greater must be capacitor esed to create the
dominantpole for the same DC gain.

Where the output transistor is a lateral PNP type
there is a pole in the regulation loop at a fre­quencybtoo low to be compensated by a capaci­tor which can be integrated. An external compen­sation is thereforenecessary so a very high value
capacitor must be connected from the output to
ground.

The paeassitic equivalent series resistance of the
capacitor used adds a zero to the regulation loop.
This zero may compromise the stability of the
system since its effect tends to cancel the effect
of the pole added. In regulatorsthis ESR must be
less than 3Ω and the minimum capacitor value is
47µF.

4/6

L4945

DIM.

MIN. TYP. MAX. MIN. TYP. MAX.

A 4.40 4.60 0.173 0.181
C 1.23 1.32 0.048 0.051
D 2.40 2.72 0.094 0.107
E 0.49 0.70 0.019 0.027

F 0.61 0.88 0.024 0.034
F1 1.14 1.70 0.044 0.067
F2 1.14 1.70 0.044 0.067

G 4.95 5.15 0.194 0.203

G1 2.40 2.70 0.094 0.106

H2 10.0 10.4 0.393 0.409

L2 16.4 0.645
L4 13.0 14.0 0.511 0.551
L5 2.65 2.95 0.104
L6 15.25 15.75 0.600 0.620
L7 6.20 6.60 0.244 0.260
L9 3.50 3.93 0.137 0.154

M 2.6 0.102

Dia 3.75 3.85 0.147 0.151

mm inch

0.116

OUTLINE AND

MECHANICAL DATA

Versawatt (TO220)

M

TO220MEC

5/6

L4945

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of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is
granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specification mentioned in this publication are
subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products
are not authorized for use as critical components in life support devices or systems without express written approval ofSTMicroelectronics.

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