Datasheet L4976D, L4976 Datasheet (SGS Thomson Microelectronics)



1A STEP DOWN SWITCHING REGULATOR

UP TO 1A STEP DOWN CONVERTER
OPERATINGINPUT VOLTAGE FROM 8V TO

55V
PRECISE5.1V REFERENCEVOLTAGE
OUTPUT VOLTAGE ADJUSTABLE FROM

3.3VTO 50V
SWITCHINGFREQUENCY ADJUSTABLE UP

TO 500KHz
VOLTAGEFEEDFORWARD
ZEROLOAD CURRENTOPERATION
INTERNAL CURRENT LIMITING (PULSE-BY-

PULSEAND HICCUPMODE)
PROTECTION AGAINST FEEDBACK DIS-

CONNECTION
THERMAL SHUTDOWN

DESCRIPTION

The L4976 is a step down monolithic power
switching regulator delivering 1A at a voltage be­tween 3.3V and 50V (selected by a simpleexter­nal divider). Realized in BCD mixed technology,
the device uses an internal power D-MOS transis­tor (with a typical Rdson of 0.25Ω) to obtain very
high efficency and high switching speed.
A switching frequency up to 250KHz is achiev­able (themaximum power dissipationof thepack-

L4976

Minidip SO16W

ORDERING NUMBERS: L4976 (Minidip)

L4976D (SO16)

ages must be observed).
A wide input voltage range between 8V to 55V
and output voltages regulated from 3.3V to 40V
cover the majority of today’s applications.
Features of this new generations of DC-DC con­verter include pulse-by-pulse current limit, hiccup
mode for short circuit protection, voltage feedfor­ward regulation, protection against feedbackloop
disconnectionand thermalshutdown.

The device is available in plastic dual in line,
MINIDIP 8 for standard assembly, and SO16W
for SMD assembly.

TYPICAL APPLICATIONCIRCUIT

Vi=8V to 55V

R

1

20K

C

2

2.7nF

May 2000

C1

220µ

63V

C

F

7

220nF

5

3

2

L4976

7

R

2

9.1K

22nF

1

C

4

6

C

6

100nF

8

4

L1

260µ

H

(77120)

D1

GI

SB360

C

8

330µF

=3.3V/1A

V

O

1/11

L4976

BLOCKDIAGRAM

2

V

REF

7

COMP

8

FB

3.3V

THERMAL

SHUTDOWN

VREF

E/A

OSCILLATOR

VOLTAGES

MONITOR

PWM

5.1V

INTERNAL

REFERENCE

3.3V

R

Q

S

DRIVE

CC

V

5

CBOOT

CHARGE

6

BOOT

CBOOT

CHARGE

AT LIGHT

LOADS

3

OSC GND OUT

1

4

PIN CONNECTIONS

GND

REF

V
OSC
OUT

1
2
3
4 VCC

FB8
COMP

7

BOOT

6
5

Minidip

N.C.
GND
V

REF

OSC

OUT
OUT

N.C.

N.C. N.C.

2
3
4
5
6
7
8

SO16W

16
15
14
13
12
11
10

9

PIN FUNCTIONS

DIP SO (*) Name Function

1 2 GND Ground
2 3 VREF 5.1V Reference voltage with 20mA current capability.
3 4 OSC An external resistor connected between the unregulated input voltage and this pin and

4 5,6 OUT Stepdown regulator output
511 V

CC Unregulated DC input voltage

6 12 BOOT A capacitor connected between this pin and OUT allows to drive the internal VDMOS
7 13 COMP E/A output to be used for frequency compensation
8 14 FB Stepdown feedback input. Connecting directly to this pin results in an output voltage of

(*) Pins 1, 7,8, 9, 10, 15 and 16 are not internally, electrically connected to the die.

a capacitor connected from this pin to ground fix the switching frequency. (Line feed
forward is automatically obtained)

3.3V. An externalresistive divider is required for higher output voltages.

N.C.1
N.C.
FB
COMP
BOOT
VCC
N.C.

2/11

THERMALDATA

Symbol Parameter Minidip SO16 Unit

R

th(j-amb)

(*) Package mounted on board.

Thermal Resistance Junction to ambient Max. 90 (*) 110 (*) °C/W

OPERATINGTEMPERATURE RATING

Symbol Parameter Value Unit

T

Junction Temperature Range -40 to 150 °C

J

ABSOLUTE MAXIMUM RATINGS

L4976

Symbol

Minidip S016

V

11

V5,V

I5,I

V12-V

V

12

V

13

V

14

P

tot

V

V

5

V

4

I

4

6-V5

V

6

V

7

V

8

Input voltage 58 V
Output DC voltage

6

Output peak voltage at t = 0.1µs f=200KHz
Maximum output current int. limit.

6

11

Bootstrap voltage 70 V
Analogs input voltage (VCC= 24V) 12 V
(VCC= 20V) 6

Power dissipation a T

Parameter Value Unit

-1

-5

V
V

14 V

V

-0.3

≤ 60°C Minidip 1W

amb

V

SO16 0.8 W

T

j,Tstg

Junction and storage temperature -40 to 150 °C

ELECTRICAL CHARACTERISTICS (Tj = 25°C, Cosc = 2.7nF, Rosc = 20kΩ,VCC = 24V, unless other-
wisespecified.) * SpecificationRefered to Tj from 0 to 125°C

Symbol Parameter Test Condition Min. Typ. Max. Unit

DYNAMICCHARACTERISTIC

V

V

o Output voltage Io = 0.5A 3.33 3.36 3.39 V

V

d Dropout voltage Vcc = 10V;Io = 1A 0.44 0.55 V

I

l Maximum limiting current Vcc = 8 to 55V * 1.5 2 2.5 A

f

s Switching frequency * 90 100 110 KHz

SVRR Supply voltage ripple rejection V

Operating input voltage range Vo= 3.3 to 50V; Io=1A * 8 55 V

I

I

o = 0.2 to 1A 3.292 3.36 3.427 V

V

cc = 8to 55V * 3.22 3.36 3.5 V

* 0.88 V

Efficiency V

Voltage stability of switching

o = 3.3V; Io =1A 85 %

+2V

i=Vcc

I

o = 1.A; f ripple = 100Hz

RMS;Vo=Vref

;

60 dB

Vcc = 8 to 55V 3 6 %

frequency
Temp. stability of switching

T

j = 0 to 125°C4%

frequency

3/11

L4976

ELECTRICAL CHARACTERISTICS (continued)

Symbol Parameter Test Condition Min. Typ. Max. Unit

Reference Section

Reference Voltage 5.0 5.1 5.2 V

I

= 0 to 10mA;

ref

V

= 8 to 55V

CC

Line Regulation I

Load Regulation V

= 0mA;

ref

V

= 8 to 55V

CC

= 0 to 5mA;

ref

V

= 0 to 20mA

CC

Short Circuit Current 30 65 100 mA

DC Characteristics

Iqop Total operating quiescent

I

q Quiescent current Duty Cycle = 0; V

current

= 3.8V 2.5 3.5 mA

FB

Error Amplifier

V

FB

R

L

V

oH High level output voltage V

V

oL Low level output voltage V

I

o source Source output current V

I

o sink Sink output current V

I

b Source bias current 2 3 µA

SVRR E/A Supply voltage ripple rejection V

gm Transconductance I

Voltage Feedback Input 3.33 3.36 3.39 V
Line regulation Vcc= 8 to 55V 5 10 mV
Ref. voltage stability vs

temperature

= 2.5V 10.3 V

FB

= 3.8V 0.65 V

FB

= 6V; VFB= 2.5V 180 220 µA

comp

= 6V; VFB= 3.8V 200 300 µA

comp

; Vcc = 8 to 55V 60 80 dB

= ∞ 50 57 dB

= -0.1 to 0.1mA

=6V

DC open loop gain R

comp=Vfb
L

comp

V

comp

OscillatorSection

Ramp Valley 0.78 0.85 0.92 V
Ramp peak Vcc= 8V 2 2.15 2.3 V

Vcc = 55V 9 9.6 10.2 V
Maximum duty cycle 95 97 %
Maximum Frequency Duty Cycle = 0%

R

osc

= 13kΩ,C

= 820pF

osc

* 4.950 5.1 5.250 V

510mV

2
6

10
25

46mA

* 0.4 mV/°C

2.5 ms

500 kHz

mV
mV

4/11

L4976

Figure1. Quiescentdraincurrent vs. input

voltage.

Iq

(mA)

200KHz
R1=22K

5

C2=1.2nF

4

3

2

Tamb=25°

C

0% DC

1

0 5 10 15 20 25 30 35 40 45 50

100KHz
R1=20K
C2=2.7nF

0Hz

D97IN724

Vcc(V)

Figure3. LineRegulation

VO
(V)

3.377

Tj=125°C

3.376

3.375

3.374

3.373

3.372

3.371

3.370
0 5 10 15 20 25 30 35 40 45 50 VCC(V)

D97IN733

Tj=25°C

Figure 2. Quiescentcurrent vs. junction

temperature

200KHz
R

=22K

1

=1.2nF

C

2

0Hz

D97IN731

Iq

(mA)

5

4

100KHz

=20K

R

1

=2.7nF

C

2

3

VCC=35V

2

0% DC

1

-50 -30 -10 10 30 50 70 90 110 Tj(°C)

Figure 4. Loadregulation

VO
(V)

3.378

3.376

3.374

Tj=25°C

3.372

3.370

Tj=125°C

3.368

3.366

3.364

3.362

3.360
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)

D97IN734

=35V

V

CC

Figure5. Switchingfrquencyvs. R1 and C2

fsw

(KHz)

500

200

0.82nF

1.2nF

100

50

20

2.2nF

3.3nF

4.7nF

5.6nF

10

5

0 20 40 60 80 R1(KΩ)

D97IN784

Tamb=25°C

Figure 6. SwitchingFrequencyvs. input

voltage.

fsw

(KHz)

107.5

105.0

102.5

Tj=25°C

100.0

97.5

95.0

92.5

90.0
0 5 10 15 20 25 30 35 40 45 50 VCC(V)

D97IN735

5/11

L4976

Figure7. Switchingfrequency vs. junction

temperature.

fsw

(KHz)

105

100

95

90

-50 0 50 100 Tj(°C)

D97IN785

Figure9. Efficiencyvs output voltage.

(%)

96
94
92
90
88
86

η

100KHz

200KHz

V
I

O

=35V

CC

=1.5A

D97IN737

Figure 8. Dropoutvoltagebetweenpin5 and 4.

∆V

(V)

0.5

0.4

0.3

0.2

0.1

0.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)

D97IN736

Tj=125°C

Tj=25°C

Tj=-25°C

Figure 10. Efficiencyvs.outputcurrent.

η

(%)

90

85

80

75

70

V

=12V

CC

V

=24V

CC

=48V

V

CC

D97IN738

VCC=8V

fsw=100KHz
VO=5.1V

84
82

0 5 10 15 20 25 VO(V)

Figure11. Efficiencyvs. outputcurrent.

η

6/11

(%)

90

85

80

75

=12V

V

CC

VCC=8V

V

=24V

CC

V

=48V

CC

70

65

60

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)

D97IN739

fsw=100KHz
VO=3.36V

65

60

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)

Figure 12. Efficiencyvs.outputcurrent.

η

(%)

90

85

80

=12V

V

CC

V

CC

V

=24V

CC

VCC=8V

=48V

75

70

65

60

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)

D97IN740

fsw=200KHz
VO=5.1V

L4976

Figure13. Efficiencyvs.outputcurrent.

η

(%)

90
85
80

VCC=8V

V

=12V

CC

=24V

V

CC

75
70

V

=48V

CC

65
60
55

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 IO(A)

D97IN741

fsw=200KHz
VO=3.36V

Figure15. Powerdissipationvs.Vcc.

I

O

=1A

I

O

D97IN743

=0.5A

Pdiss
(mW)

800

600

400

200

=5.1V

V

O

fsw=100KHz

IO=1.5A

Figure 14. Efficiencyvs.Vcc.

η

(%)

85

80

75

70

0 1020304050VCC(V)

IO=1.5A

V

0

V

0

=5.1V-f

=5.1V-f

V

V

0

=3.36V-f

SW

SW

0

=3.36V-f

Figure 16. Efficiencyvs.Vo.

Pdiss
(mW)

800

600

400

200

V

=35V

CC

fsw=100KHz

=100KHz

=200KHz

SW

SW

=

1

200KHz

IO=1.5A

I

O

D97IN742

=100KHz

D97IN744

I

=1A

O

=0.5A

0

0 1020304050VCC(V)

Figure17. Pulseby pulse limitingcurrent vs.

junctiontemperature.

Ilim

(A)

2.9

fsw=100KHz
VCC=35V

2.8

2.7

2.6

2.5

2.4

2.3

-50 -25 0 25 50 75 100 125 Tj(°C)

D97IN747

0

0 5 10 15 20 25 30 V0(V)

Figure 18. Load transient.

7/11

L4976

Figure19. Line transient.

V

CC

(V)

30

20
10

1

2

1ms/DIV

IO=

1A

fsw= 100KHz

D97IN786

V

O

(mV)

100

0

-100

Figure 20. Openloopfrequencyandphaseof er-

roramplifier

GAIN

(dB)

50

0

-50

-100

-150

-200
10 10

3

2

10

5

4

10

10

6

GAIN

Phase

10

7

D97IN787

8

10

Phase

0

45

90

135

f(Hz)10

8/11

L4976

DIM.

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

A 3.32 0.131

a1 0.51 0.020

B 1.15 1.65 0.045 0.065

b 0.356 0.55 0.014 0.022

b1 0.204 0.304 0.008 0.012

D 10.92 0.430
E 7.95 9.75 0.313 0.384

e 2.54 0.100
e3 7.62 0.300
e4 7.62 0.300

F 6.6 0.260

I 5.08 0.200

L 3.18 3.81 0.125 0.150

Z 1.52 0.060

mm inch

OUTLINE AND

MECHANICAL DATA

Minidip

9/11

L4976

DIM.

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

A 2.35 2.65 0.093 0.104

A1 0.1 0.3 0.004 0.012

B 0.33 0.51 0.013 0.020

C 0.23 0.32 0.009

D 10.1 10.5 0.398 0.413

E 7.4 7.6 0.291 0.299

e 1.27 0.050

H 10 10.65 0.394 0.419

h 0.25 0.75 0.010 0.030

L 0.4 1.27 0.016 0.050

K0°(min.)8° (max.)

mm inch

0.013

OUTLINE AND

MECHANICAL DATA

SO16 Wide

10/11

L

hx

45

A

B

e

K

A1

C

H

D

16

9

E

1

8

L4976

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