SGS Thomson Microelectronics L4990D, L4990A, L4990 Datasheet

L4990



CURRENT-MODECONTROLPWM
SWITCHINGFREQUENCYUP TO 1MHz
LOW START-UPCURRENT < 0.45mA
HIGH-CURRENT OUTPUT DRIVE SUITABLE

FOR POWER MOSFET(1A)
FULLY LATCHED PWM LOGIC WITH DOU-

BLE PULSESUPPRESSION
PROGRAMMABLEDUTY CYCLE
100% AND 50% MAXIMUM DUTY CYCLE

LIMIT
PROGRAMMABLESOFTSTART
PRIMARY OVERCURRENT FAULT DETEC-

TION WITH RE-START DELAY
PWMUVLO WITH HYSTERESIS
IN/OUTSYNCHRONIZATION
DISABLELATCHED
INTERNAL 100ns LEADING EDGE BLANK-

ING OF CURRENT SENSE
PACKAGE:DIP16ANDSO16W

DESCRIPTION

This primary controller I.C., developedin BCD60II
technology, has been designed to implement off

L4990A

PRIMARY CONTROLLER

MULTIPOWER BCD TECHNOLOGY

DIP16 SO16W

ORDERING NUMBERS:

line or DC-DC power supply applications using a
fixedfrequency current mode control.
Based on a standard current mode PWM control­ler this device includes some features as pro­grammable soft start, IN/OUT synchronization,
disable (to be used for over voltage protection
and for power management), precise maximum
Duty Cycle Control, 100ns (typ) leading edge
blanking on current sense, pulse by pulse current
limit and overcurrent protection with soft start in­tervention.

L4990/L4990A(DIP16)

L4990D/L4990AD (SO16W)

BLOCK DIAGRAM

RCT

3

DC

14

DIS

2.5V

13

ISEN

1.2V

SS

7

July 1999

+

-

-

+

OVER CURRENT

+

-

DIS

BLANKING

1V R

SYNC DC-LIM

TIMING2

T

PWM

FAULT

SOFT-START

2R

12

SGND COMP

25V

16V/10V

VREF OK

CLK

DIS

V

CC

Vref

+

PWM UVLO

-

SQ
R

2.5V

+

E/A

-

6

13V

VREF

48151

D98IN1002

9

V

C

10

OUT

11

PGND

5

VFB

1/24

L4990 - L4990A

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

CC Supply Voltage (I

I

OUT

Output Peak Pulse Current 1.5 A
Analog Inputs & Outputs (6,7) -0.3 to 8 V
Analog Inputs & Outputs (1,2,3,4,5,15,14 13) -0.3 to 6 V

P

tot

T

j

T

stg

(*) maximum package power dissipation limits must be observed

Power Dissipation @ T
Junction Temperature, Operating Range -25 to 125
Storage Temperature, Operating Range -55 to 150

PIN CONNECTION

< 50mA) (*) selflimit V

CC

=70°C1W

amb

C

°

C

°

SYNC

RCT

DC

VREF

VFB

COMP

SS

V

CC

1
2
3
4
5
6
7 OUT

15
14
13
12
11
10

8V

D95IN197

N.C.16
DC-LIM
DIS
ISEN
SGND
PGND

9

C

THERMAL DATA

Symbol Parameter Value Unit

R

th j-amb

R

th j-amb Thermal Resistance Junction to Ambient

Thermal Resistance Junction to Ambient DIP16 80 °C/W

SO16

120 °C/W

PIN FUNCTIONS

N. Name Function

1 SYNC Synchronization. A synchronization pulse terminates the PWM cycle and discharges Ct
2 RCT Oscillator pin for external C
3 DC Duty Cycle control
4 VREF 5.0V +/-1.5% reference voltage
5 VFB Error Amplifier Inverting input
6 COMP Error Amplifier Output
7 SS Soft start pin for external capacitor Css
8V
9V

CC

C

Supply for internal ”Signal” circuitry

Supply for Power section
10 OUT High current totem pole output
11 PGND Power ground
12 SGND Signal ground
13 ISEN Current sense
14 DIS Disable. It must never be leftfloating. Tie to SGND if not used.
15 DC-LIM Connecting this pin to Vref, DC is limitedto 50%. If it is left floating or grounded no limitation is

imposed
16 NC Not connected

components

t,Rt

2/24

L4990 - L4990A

ELECTRICALCHARACTERISTICS

CC

= 15V; Tj=0 to 70°C; unless otherwisespecified.)

(V

Symbol Parameter Test Condition Min. Typ. Max. Unit

REFERENCE SECTION

V

O

T

S

Output Voltage Tj=25°C; IO= 1mA 4.925 5.0 5.075 V
Line Regulation V
Load Regulation I

= 12 to 20V 2.0 15 mV

CC

= 1 to 20mA 5.0 20 mV

O

Temperature Stability 0.4 mV/°C
Total Variation Line, Load,Temperature 4.875 5.0 5.125 V

I

OS

Short Circuit Current Vref = 0V 30 150 mA
Power Down/UVLO V

= 8.5V; I

CC

= 0.5mA 0.2 0.5 V

sink

OSCILLATOR SECTION

Initial Accuracy T

Accuracy R

Initial Accuracy T

Accuracy R

Duty Cycle pin 3 = 0,7V, pin 15 = Vref

Duty Cycle R

=25°C; RT= 4.42kΩ;

j

C

= 1nF; pin 15 Vref

T

= 4.42KΩ;VCC= 12 to 20V;

T

C

= 1nF; pin 15 = Vref

T

=25°C; RT= 4.42KΩ;

j

C

= 1nF; pin 15 OPEN

T

= 4.42KΩ;VCC= 12 to 20V;

T

C

= 1nF; pin 15 OPEN

T

pin 3 = 0.7V, pin 15 = OPEN

= 4.42kΩCT= 1nF

T

pin 3 = 3.2V, pin 15 = Vref
pin 3 = 3.2V, pin 15 = OPEN

285 300 315 kHz

279 300 321 kHz

280 295 310 kHz

275 295 315 kHz

0
0

45

90
Duty Cycle Accuracy pin 3 = 2.02V,pin 15 = OPEN 37 40 43 %
Oscillator Ramp Peak 3.0 V
Oscillator Ramp Valley 1.0 V

ERROR AMPLIFIER SECTION

Input Bias Current V

V

I

G

OPL

Input Voltage V
Open Loop Gain V

SVR Supply Voltage Rejection V

OL Output Low Voltage I

V

OH Output High Voltage I

V

I

O

Output SourceCurrent V
Output Sink Current V

to GND 0.2 1.0 µA

FB
COMP=VFB

= 2 to 4V 60 90 dB

COMP
CC = 12 to 20V 85 dB

= 2mA, VFB= 2.7V 1.1 V

sink

= 0.5mA, VFB= 2.3V 5 6 V

source

> 4V,VFB= 2.3V 0.5 1.3 mA

COMP

= 1.1V,VFB= 2.7V 2 6 mA

COMP

2.42 2.5 2.58 V

Unit Gain Bandwidth 2 4 MHz

S

R

Slew Rate 8 V/µs

PWM CURRENT SENSE SECTION

I

b

I

S

Input Bias Current I
Maximum Input Signal V

=0 3 15 µA

sen

= 5V 0.92 1.0 1.08 V

COMP

Delay to Output 100 ns
Gain 2.85 3 3.15 V/V

SOFT START

I

SSC

I

SSD

V

SSSAT

V

SSCLAMP

SS Charge Current 14 20 26
SS Discharge Current VSS = 0.6V 200
SS Saturation Voltage DC = 0% 0.6 V
SS Clamp Voltage 7 V

LEADING EDGE BLANKING

Internal Masking Time 100 ns

%
%

%
%

A

µ

A

µ

3/24

L4990 - L4990A

ELECTRICALCHARACTERISTICS

(continued.)

Symbol Parameter Test Condition Min. Typ. Max. Unit

OUTPUT SECTION

V

OL

V

OH

V

OUT CLAMP

Output Low Voltage IO= 250mA 1.0 V
Output High Voltage IO= 20mA; VCC= 12V 10 10.5 V

= 200mA; VCC= 12V 9 10 V

I

O

Output Clamp Voltage IO= 5mA; VCC = 20V 13 V
Collector Leakage V
Fall Time C

Rise Time C

UVLO Saturation V

CC = 20V VC = 24V 100 200 µA

= 1nF

O

C

= 2.5nF

O

= 1nF

O

C

= 2.5nF

O

CC =0VtoV

CCON;Isink

= 10mA 1.0 V

20
35

50
70

60 ns

100 ns

SUPPLY SECTION

V

CCON

V

CCOFF

V

hys Voltage AfterTurn-onHysteresis

I

S

I

op

I

q

I

SH

V

Z

Startup voltage

Minimum Operating Voltage L4990

Start Up Current Before Turn-on at:

Operating Current CT=1nF,RT=4.42kΩ,CO=1nF 12 18 mA
Quiescent Current (After turn on), Co =0nF

Shutdown Current 100 270 450
Zener Voltage I8= 20mA 21 25 30 V

V

=V

CC

C

= 1nF, RT= 4.42kΩ,

T

CCON

- 0.5V

L4990

L4990A157.8

9

L4990A

L4990

L4990A

7

5.5

0.5

100 270 450

16

8.4
10

7.6

17

9

11

8.2

6

0.8

7.0 10 mA

SYNCHRONIZATION SECTION

Master Operation

V

1

I

1

Clock Amplitude I
Clock Source Current Vclock = 3.5V 7 mA

= 0.8mA 4 V

SOURCE

Slave Operation

V

1

Sync Pulse Low Level 1 V

High Level 3.5 V

I

1

Sync Pulse Current VSYNC = 3.5V 0.8 mA

OVER CURRENT PROTECTION

V

t

Fault Threshold Voltage 1.1 1.2 1.3 V

DISABLE SECTION

Shutdown threshold 2.4 2.5 2.6 V

ns

ns

µ

µ

V
V

V

v

V

v

A

A

FUNCTIONAL DESCRIPTION

The I.C. contains a standard PWM current mode
control section with improved performance with
respectto the UC384Xfamily.
Enhanced features include start-up bias current
reduced to < 270µA (typ), improved E/A perform­ance (4MHz B/W, 1.3mA Source Current, high­slew rate) accurate 1MHz oscillator, and also re­duced propagation delays in the critical path from
Current Sense to Output.

4/24

ADDITIONALFEATURES

SoftStart (SS)

An external capacitor is charged by an internal
constant current source (20µA) to generate a SS
signal which clamps the E/A output
The SS pin doubles as a Fault Reset Delay func­tion as describedbelow.

Current Limit/ Reset Delay

An internal high-speed current limit comparator

L4990 - L4990A

referenced to 1.2V detects primary over-current
conditions. On detection of an overcurrent fault
the output is immediately shutdown and the fault
is also latched. A Fault Reset Delay is imple­mented by discharging the external Soft Start
(SS) timing capacitor before resetting the fault
latch and initiating a softstart cycle.
In case of a continuous fault condition the SS ca­pacitor is charged to 5V before being discharged
again, to ensure that the fault frequency does not
exceed the programmedsoft start frequency.

Duty CycleLimit

A simple connectionbetween the DC-LIM and the
available Vref activatesan internal T- FlipFlop lim­iting the DC to about 50%. If this pin is not con­nected or grounded, the limit of the duty cycle is
extended to about 100%

Duty CycleControl

Duty Cycle DC is externally programmed by set­ting a voltage between 1V (0% DC) and 3V
(100% DC) at the DC pin. The programmed volt­age is compared with the oscillator C

capacitor

T

charging waveform to determine the maximum
ON-time in each period. This function gives a fine
control of DC.
If this pin is floating the maximum duty cycle de­pends on DC-LIM status.

Synchronization

A SYNC pin eases Synchronization of the IC to
the external world ( e.g. another IC working in

parallelor to TV/monitorsyncsignal).
In TV/monitor applications the timing components

,CTare set for a frequency lower than the

R

T

minimum TV sync frequency.When the TV circuit
has powered-up it takes over and the system fre­quencyis that of the SYNC. Duty Cycle is control­lableusing the DC function.
In parallel operation of several IC’s no Mas­ter/Slavedesignationis requiredas the higherfre­quency IC is automaticallythe master. Controllers
to be synchronized have their SYNC pins tied to­gether and each SYNC pin operatesas a bidirec­tional circuit. The first IC to drive its SYNC pin is
the master and it initiates a discharge of the C
timing capacitor of every controller. The Sync in­put signal is edge-triggered and sets an internal
”sync latch” which ensures full discharge of C

.

T

DisableFunction

The DIS pin performs a logic level latched-shut­down function. When pulled above 2.5V it shuts
down the complete IC with a standby current of
<270µA(typ).

To reset the IC the V

pin must be pulled-down

CC

belowthe lower UVLO threshold (10V).

LeadingEdge Blanking (LEB)

An LEB interval of 100ns has been incorporated
into the IC to blank out the current sense signal
during the first 100ns from switch turn-on.
This provides noise immunity to turn-on spikes
and reduces external RC filteringrequirementson
the current-sensesignal.

T

Figure 1. Quiescentcurrent vs. input voltage.

(X = 7.6V and Y = 8.4V for L4990A)

Iq [mA]

30

20

8

6

1

0.8

0.6

0.4

0.2
0

0 4 8 12162024

V14 = 0, OSC=disabled
Tj = 25°C

X

Vcc [V]

Y

Figure2. Quiescentcurrentvs. input voltage

(after disable).

Iq [uA]

300

270

240

210

8 1012141618202224

Vcc [V]

V14 = Vref

Tj = 25°C

5/24

L4990 - L4990A

Figure 3. Quiescentcurrent vs. input voltage.

Iq [m A ]

9.0

V14 = 0, V5 = Vref

8.5

8.0

7.5

7.0

8 1012141618202224

igure5. Quiescentcurrent vs. input voltage

F

Iq [mA]

36

30

24

Rt = 4 .5 Kohm ,Tj = 2 5°C

1M hz

500Khz
300Khz

100Khz

Vcc [V]

and switching frequency.

Co = 1nF, Tj = 25°C

DC = 100%

1MHz

igure4. Quiescentcurrentvs. input voltage

F

and switching frequency.

Iq [mA]

36

30

24

18

12

6

0

8 10121416182022

Co = 1nF, Tj = 25°C

DC = 0%

1MHz

500KHz

300KHz
100KHz

Vcc [V]

Figure6. Referencevoltage vs. load current.

Vref [V]

5.1

5.05

Vcc=15V
Tj = 25°C

18

12

500KHz
300KHz

100KHz

6

0

8 10121416182022

Vcc [V]

Figure 7. Vref vs. junction temperature.

Vref [V])

5.1

5.05

5

4.95

Vcc = 15V
Iref = 1mA

5

4.95

4.9
0 5 10 15 20 25

Iref [mA]

Figure8. Vref vs. junctiontemperature.

Vref [V]

5.1

Vcc = 15V

5.05

5

4.95

Iref= 20mA

4.9

-50 -25 0 25 50 75 100 125 150
Tj (°C)

6/24

4.9

-50 -25 0 25 50 75 100 125 150
Tj (°C)

L4990 - L4990A

Figure 9. Vref SVRR vs. switchingfrequency.

SVRR (dB)

120

80

40

0

1 10 100 1000 10000

fsw (Hz)

Vcc=15V
Vp-p=1V

Figure 11. Outputsaturation.

Vsat = V [V]

2.5

1.5

10

2

Vcc = 15V
Tj= 25°C

Figure10. Output saturation.

Vsat = V [V]

16

14

12

10

10

Vcc = 15V
Tj = 25°C

8

6

0 0.2 0.4 0.6 0.8 1 1.2

Isource [A]

Figure12. UVLO Saturation

Ipin10 [mA]
50

40

30

Vcc < Vccon

beforetu rn-on

1

0.5

0

0 0.2 0.4 0.6 0.8 1 1.2

Isink [A]

Figure13.Timingresistorvs.switchingfrequency.

fsw(KHz)

5000
2000

Vcc =15V,V15=0V
Tj= 25° C

1000

50 0
20 0

10 0

50
20

5.6nF

2.2nF

100p F
220pF

470pF

1nF

10

10 20 30 40

Rt (kohm)

20

10

0

0 200 400 600 800 1,000 1,200 1,400

Vpin10 [mV]

Figure14. Switchingfrequencyvs. temperature.

fsw (KHz)
320

Rt= 4.5Kohm, Ct = 1nF

310

300

290

280

-50 -25 0 25 50 75 100 125 150

Vcc = 15V, V15=Vref

Tj (°C)

7/24

L4990 - L4990A

Figure 15. Switchingfrequencyvs. temperature.

fsw (KHz)
320

Rt= 4.5Kohm, Ct = 1nF

310

300

290

280

-50 -25 0 25 50 75 100 125 150

Vcc = 15V,V15= 0

Tj (°C)

Figure 17. Maximum Duty Cycle vs Vpin3.

DC ControlVoltage Vpin3 [V]

3.5

V15 = Vref

3

2.5

V15 = 0V

Figure16. Dead time vs Ct.

Dead time[ns]

1,500

Rt=4.5Kohm

V15= 0V

1,200

900

V15= Vref

600

300

246810

TimingcapacitorCt [nF]

Figure18.Delaytooutputvsjunctiontemperature.

Delayto output (ns)

130

120

110

100

2

Rt = 4.5Kohm,

1.5

Ct = 1nF

1

0 102030405060708090100

Duty Cy cle [%]

Figure 19. E/A frequencyresponse.

G [dB]

150

100

50

0

0.01 0.1 1 10 100 1000 10000 100000
f(KHz)

Phase

140

120

100

80

60

40

20

90

80

70

60

-50 -25 0 25 50 75 100 125 150
Tj(°C)

PIN10=OPEN

1Vpulse
onPIN13

8/24