ST L4916 User Manual

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VOLTAGEREGULATOR PLUSFILTER

.FIXEDOUTPUTVOLTAGE8.5 V

.

250mAOUTPUTCURRENT

.HIGH RIPPLEREJECTION

.HIGH LOADREGULATION

.HIGH LINE REGULATION

.SHORT CIRCUIT PROTECTION

.

THERMAL SHUTDOWN WITHHYSTERESIS

.DUMP PROTECTION

DESCRIPTION

Thiscircuitcombinesbothafilterandavoltageregu­latorin orderto providea highripplerejectionovera
widerinput voltagerange.

A supervisorlow-pass loopof theelement prevents
theoutputtransistorfromsaturationat lowinputvolt­ages.

The non linear behaviour of this control circuitry
allowsa fastsettlingofthefilter.

POWER MI NIDIP

(4 + 4)

ORDERING NUMBER :

L4916

L4916

BLOCK DIAGRAM

June 2000

1/8

L4916

PI N CONNE CTI ON (top view)

ABSOLUTEMAXIMUMRATINGS

Symbol Parameter Value Unit

Peak Input Voltage (300 ms) 40 V

V

i

DC Input Voltage 28 V

V

i

Output Current Internally Limited

I

O

Power Dissipation Internally Limited

P

tot

T

stg,Tj

Storage and Junction Temperature – 40 to 150

°C

THERMAL DATA

Symbol Parameter Value

R

th j-amb

R

th j-pins

Thermal Resistance Junction-ambient
Thermal Resistance Junction-pins

Max
Max

80
20

Unit

C/W

°
°C/W

2/8

L4916

(T

ELECTRICALCHARACTERISTICS

Symbol Parameter Test Conditions Min. Typ. Max. Unit

Input Voltage 20 V

V

i

Output Voltage Vi=12to18V

V

O

∆V

∆

∆

∆

∆

SVR Supply Voltage Rejection V

(* ) Dependi ng of t he CFTcapaci t or .

Controlled Input-output Dropout

I/O

Voltage
Line Regulation Vi=12to18V

V

O

Load Regulation IO= 5 to 250mA

V

O

Load Regulation

V

O

(filter mode)

Quiescent Current IO=5mA 1 2 mA

I

q

Quiescent Current Change Vi= 6 to 18 V

I

∆

q

Output Voltage Drift I

V

O

T

∆

Short Circuit Current 250 300 mA

I

SC

Switch On Time IO= 150 mA

T

on

Thermal Shutdown Junction

T

J

Temperature

=25°C;Vi=13.5V, testcircuitoffig.1, unlessotherwisespecified)

amb

8.1 8.5 8.9 V

= 5 to 150mA

I

O

Vi= 5 to 10 V

= 5 to 150mA

I

O

1.6 2.1 V

120mV

=10mA

I

O

50 100 mV

=30µs

t

on

=≥1ms

t

off

Vi= 8.5 V

= 5 to 150mA

I

O

=30µs

t

on

=≥1ms

t

off

150 250 mV

0.05 mA

I

= 5 to 150mA

O

= 10 mA 1.2

O

=1V

iac

rms

f = 100 Hz

= 150 mA

I

O

=12to18V

V

IDC

= 6 to 11 V

V

IDC

= 5 to 11 V

V

i

=11to18V

V

i

70

35(*)

500(*)

300
145 °

mV/°C

dB
dB

ms
ms

C

Figure1 :

Testand ApplicationCircuit.

3/8

L4916

Figure2 : P.C.Board and ComponentLayoutof Fig.1 (1 : 1scale).

PRI N CI PLE OF OPERATIO N

During normal operation (input voltageupper than
V

I MIN=VOUT NOM

+ ∆V

). Thedevice works as a

I/O

normalvoltageregulatorbuiltaroundtheOP1ofthe
blockdiagram.

The series pass elementuse a PNP-NPN connec­tionto reducethedropout.Thereferencevoltageof
theOP1isderivedfromaREFthroughtheOP2and
Q3, actingas an active zenerdiode of valueV

REF

Inthisconditionthedeviceworksintherange(1) of
the characteristicof the non linear dropcontrolunit
(seefig.3).

The outputvoltageis fixedto itsnominalvalue:

V

OUT NOM=VREF

R1

(1+ )=

R2

V

CFT

R1

(1 + )

R2

R1

=INTERNALLYFIXED RATIO= 2.4

R2
The ripple rejectionis quite high (70 dB)and inde-

pendentfrom C

FT

value.

Ontheusualvoltageregulators,whentheinputvol­tage goes belowthe nominal value, theregulation
transistors (series element) saturate bringing the
systemout of regulation makingit very sensible to
everyvariationoftheinput voltage.Onthecontrary,
a controlloop on the L4916 consentsto avoidthe
saturation of the series element by regulating the
valueof thereferencevoltage(pin2).Infact,when­ever the inputvoltage decreases below V

I MIN

the
supervisorloop, utilizing a non linear OTA, forces
the reference voltage at pin 2 to decreaseby dis­chargingC

. So,during thestaticmode,whenthe

FT

input voltagegoes below V
fixed to about 1.6V. In this condition the device
worksasa lowpassfilterintherange(2)of theOTA
characteristic. The ripple rejectionis externallyad­justableacting onC

.

1+

Where:
gm =2.10

R1

= fixed ratio

R2
C

FT

=valueof capacitorin µF

Thereactiontimeof the supervisorloopis given by
thetransconductanceoftheOTAandbyC
the valueof theripplevoltageis so high and its ne­gativepeakis fast enough to determinean istanta­neous decrease of the dropouttill 1.2 V, the OTA
works in a higher transconductance condition
[range (3) of the characteristic] and dischargethe
capacitorrapidously.

If the ripple frequencyis high enoughthe capacitor
won’t chargeitselfcompletely,andthe output volt­agereachesasmallvalueallowingabetterripplere­jection; the device’sagainworkingas a filter(fast
transientrange).

WithC

=10µF; f=100Hza SVRof35isobtained.

FT

the drop out iskept

MIN

asfollows:

FT

(jw)

V

V

(1 + )

FT

out

I

10

(jw)

-6

R

2

SVR(jw) = =

gm R1
jwC

-5Ω-1

=OTA’Stypicaltransconductance

valueon linearregion

.When

FT

4/8

Figure 3 : NonlinerTransferCharacteristicof the Drop ControlUnit.

L4916

1) Normaloperating range (high ripple
rejection)

2)Dropcontrolledrange(medium ripple
rejection)

3) Fast discharge of C

FT

Figure 4 : SupplyVoltageRejection vs.Input

Voltage.

Figure 6 :V

vs. SupplyVoltage. Figure7 : QuiescentCurrentvs. InputVoltage.

o

Figure5 : SupplyvoltageRejectionvs.

Frequency.

5/8

L4916

Figure 8 : Dropoutvs.LoadCurrent.

Figure 9 : InhibitFunctionRealizedonC

FT

Pin.

6/8

L4916

DIM.

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

A 3.3 0.130

a1 0.7 0.028

B 1.39 1.65 0.055 0.065

B1 0.91 1.04 0.036 0.041

b 0.5 0.020

b1 0.38 0.5 0.015 0.020

D 9.8 0.386
E 8.8 0.346

e 2.54 0.100
e3 7.62 0.300
e4 7.62 0.300

F 7.1 0.280

I 4.8 0.189
L 3.3 0.130
Z 0.44 1.6 0.017 0.063

mm inch

OUTLINE AND

MECHANICAL DATA

PowerMinidip

7/8

L4916

Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the conse­quences 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 of STMicroelectronics.

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8/8

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