ST L5991, L5991A User Manual

L5991

®

PRIMARY CONTR OLL ER WI TH STANDBY

CURRENT-MODE CONTROL PWM SWITCHING FREQUENCY UP TO 1MHz LOW START-UP CURRENT (< 120µA) HIGH-CURRENT OUTPUT DRIVE SUITABLE

FOR POW E R MO S F ET (1 A ) FULLY LATCHED PWM LOGIC WITH DOU-

BLE PULSE SUPPRESSION PROGRAMMABLE DUTY CY CLE 100% AND 50% MAX IMUM DU TY C YCLE LI MIT STANDBY FUNCTION PROGRAMMABLE SOFT START PRIMARY OVERCURRENT FAULT DETEC-

TION WITH RE-START DELAY PWM UV LO W I T H H YS T ERESIS IN/OUT SYNCHRONIZATION LATCHED DISABLE INTERNAL 100ns LEADING EDGE BLANK-

ING OF CURRENT SENSE PACKAGE: DIP16 AND SO16

DESCRIPTION

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

L5991A

MULTIPOWER BCD TECHNOLOGY

DIP16 SO16

ORDERING NUMBERS:

L5991D/L5991AD (SO16)

line or DC-DC power supply applications using a fixed frequency current mode control. Based on a standard current mode PWM controller this device includes some features such 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 leading edge blanking on current sense, pulse by pulse current limit, overcurrent protection with soft start intervention, and Standby function for oscillator frequency reduction when the converter is lightly loaded.

L5991/L5991A (DIP16)

BLOCK DIAGRAM

2

RCT

3

DC

14

DIS

2.5V

13

ISEN

1.2V

SS

7

August 2001

+

-

+

OVER CURRENT

+

-

DIS

BLANKING

1V R

SYNC DC-LIM

TIMING

T

PWM

FAULT

SOFT-START

2R

12

SGND COMP

25V

15V/10V

VREF OK

CLK

DIS

V

CC

Vref

+

PWM UVLO

-

SQ R

STAND-BY

+

2.5V

E/A

-

6

13V

VREF

VREF 48151

D97IN725A

9

V

C

10

OUT

11

PGND

16

ST-BY

5

VFB

1/23

L5991 - L5991A

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

CC

I

OUT

P

tot

T

j

T

stg

(*) maximum package power dissipation limits must be observed

PIN CONNECTION

Supply Voltage (ICC < 50mA) (*) selflimit V 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, 16) -0.3 to 6 V Power Dissipation @ T

@ T

= 70°C (DIP16)

amb

= 50°C (SO16)

amb

1

0.83 Junction Temperature, Operating Range -40 to 150 °C Storage Temperature, Operating Range -55 to 150 °C

W W

SYNC

RCT

DC

VREF

VFB

COMP

SS

V

CC

1 2 3 4 5 6 7OUT 8V

15 14 13 12 11 10

ST-BY16 DC-LIM DIS ISEN SGND PGND

9

C

THERMAL DATA

Symbol Parameter Value Unit

R

th j-amb

Thermal Resistance Junction -Ambient Thermal Resistance Junction -Ambient

(DIP16) (SO16)

80 °C/W

120 °C/W

PIN FU NCTIONS

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 @ 25°C 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 left floating. TIE to SGND if not used. 15 DC-LIM Connecting this pin to Vref, DC is limited to 50%. If it is left floating or grounded no limitation is

imposed 16 ST-BY Standby. Connect a resistor to RCT. Connect to VREF or floating if not used.

, RA, RB components

T

2/23

L5991 - L5991A

ELECTRICAL CHARACTERI STICS

CC

= 15V; Tj = 0 to 105°C; RT = 13.3kΩ (*) CT = 1nF;

(V

unless otherwise specified.)

Symbol Parameter Test Condition Min. Typ. Max. Unit

REFERENCE SECTION

V

REF

T

S

I

OS

OSCILLATOR SECTION

ERROR AMPLIFIER SECTION

V

I

G

OPL

SVR Supply Voltage Rejection V

V

OL

V

OH

I

O

S

R

PWM CURRENT SENSE SECTION

I

b

I

S

V

t

SOFT START SECTION

I

SSC

I

SSD

V

SSSAT

V

SSCLAMP

LEADING EDGE BLANKING

OUTPUT SECTION

V

OL

V

OH

V

OUT CLAMP

(*) RT = RA//RB, RA = RB = 27kΩ, see Fig. 23.

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

= 12 to 20V; Tj = 25°C 2.0 10 mV

CC

= 1 to 10mA; Tj = 25°C 2.0 10 mV

O

Temperature Stability 0.4 mV/°C Total Variation Line, Load, Temperature 4.80 5.0 5.130 V Short Circuit Current Vref = 0V 30 150 mA Power Down/UVLO V

= 6V; I

CC

Initial Accuracy pin 15 = Vref; T

pin 15 = Vref; V V

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

pin 3 = 0.7V, pin 15 = OPEN pin 3 = 3.2V, pin 15 = V

pin 3 = 3.2V, pin 15 = OPEN

= 0.5mA 0.2 0.5 V

sink

= 25°C; V

j

= 12 to 20V

CC

comp

= 12 to 20V

CC

comp

= 4.5V 95 100 105 kHz

comp

93 100 107 kHz

= 4.5V

46.5 50 53.5 kHz

= 2V

REF

0 0

REF

47

93 Duty Cycle Accuracy pin 3 = 2.79V, pin 15 = OPEN 75 80 85 % Oscillator Ramp Peak 2.8 3.0 3.2 V Oscillator Ramp Valley 0.75 0.9 1.05 V

Input Bias Current V Input Voltage V Open Loop Gain V

Output Low Voltage I Output High Voltage I Output Source Current V Output Sink Current V

to GND 0.2 3.0 µA

FB

= V

COMP COMP

CC sink source

COMP

FB

= 2 to 4V 60 90 dB

= 12 to 20V 85 dB

= 2mA 1.1 V

= 0.5mA, VFB = 2.3V 5 6 V

> 4V, VFB = 2.3V 0.5 1.3 2.5 mA = 1.1V, VFB = 2.7V 2 6 mA

2.42 2.5 2.58 V

Unit Gain Bandwidth 1.7 4 MHz Slew Rate 8 V/µs

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 70 100 ns Gain 2.85 3 3.15 V/V Fault Threshold Voltage 1.1 1.2 1.3 V

SS Charge Current Tj = 25°C 142026µA SS Discharge Current VSS = 0.6V Tj = 25°C 5 10 15 µA SS Saturation Voltage DC = 0% 0.6 V SS Clamp Voltage 7 V

Internal Masking Time 100 ns

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

I

= 200mA; VCC = 12V 9 10 V

O

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

= 20V VC = 24V 2 20 µA

CC

% %

3/23

L5991 - L5991A

ELECTRICAL CHARACTERI STICS

(continued.)

Symbol Parameter Test Condition Min. Typ. Max. Unit

OUTPUT SECTION

Fall Time C

O

C

O

= 1nF = 2.5nF

Rise Time CO = 1nF

C

= 2.5nF

O

UVLO Saturation VCC = VC = 0 to V

CCON; Isink

= 10mA 1.0 V

20 35

50 70

60 ns

100 ns

SUPPLY SECTION

V

CCON

V

CCOFF

V

Startup voltage Minimum Operating

Voltage

hys

I

S

I

op

I

q

V

Z

UVLO Hysteresis Start Up Current Before Turn-on at:

V

= VC = V

CC

CCON

-0.5V Operating Current CT = 1nF, RT = 13.3kΩ, CO =1nF 9 13 mA Quiescent Current (After turn on), CT = 1nF,

R

= 13.3kΩ, CO =0nF

T

Zener Voltage I8 = 20mA 21 25 30 V

L5991

L5991A

L5991

L5991A

L5991

L5991A

14

7.8 9

7

4.5

0.5

15

8.4 10

7.6

5

0.8

16

9

11

8.2

40 75 120 µA

7.0 10 mA

STANDBY FUNCTION

I

V

REF-VST-BY

V

T1

Standby Threshold V

= 2mA 45 mV

ST-BY

Falling 2.5 V

comp

V

Rising 4.0 V

comp

SYNCHRONIZATION SECTION

Master Operation

V

1

I

1

Clock Amplitude I Clock Source Current Vclock = 3.5V 3 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 0.5 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

= 0 to 3V -1 1 µA

pin14

VCC = 15V 330 µA

I

qSH

Input Bias Current V Quiescent current After

Disable

Figure 1. L5991 - Quiescent current vs. input

voltage. (X = 7.6V and Y= 8.4V for L5991A)

Iq [m A ]

30 20

8 6

4

0.2

0.15

0.1

0.05 0

04 8

V14 = 0, Pin2 = open

Tj = 25°C

X

12 16 20 24

Y

Vcc [V]

28

Figure 2. L5991 - Quiescent current vs. input

voltage (after disable). (X = 7.6V and Y= 8.4V for L5991A)

Iq [µ A ]

350 300 250 200 150 100

50

0

0 4 8 12 16 20 24

X

Vcc [V]

V14 = Vref Tj = 25 °C

Y

ns ns

V V

4/23

)

L5991 - L5991A

Figure 3. Quiescent current vs. input voltage.

Iq [m A ]

9.0

V14 = 0, V5 = Vref

8.5

8.0

7.5

7.0 8 1012141618202224

Rt = 4.5Kohm,Tj = 25°C

1Mhz

500K hz 300K hz

100K hz

Vc c [V]

Figure 5. Quiescent current vs. input voltage

and switching fre que nc y .

Iq [mA ] 36

Co = 1nF, Tj = 25°C

30

24

18

12

6

0

8 10121416182022

DC = 100 %

1MHz

500KHz 300KHz

100KHz

Vcc [V]

Figure 4. Quiescent current vs. input voltage

and switching frequency.

Iq [m A] 36

30

24

18

12

6

0

Co = 1nF, Tj = 25°C DC = 0%

1MHz

500KHz 300KHz

100KHz

8 10121416182022

Vcc [V]

Figure 6. IC Consumption vs. Temperature.

[mA]

100

10

Quiescent current

Vcc =15V, after turn-on

RT=13.3 kΩ, CT=1nF

1

DC = 0

0.1

Start-up current

Vc=Vcc= Vccon-0.5V , before turn-on

0.01

-50 -25 0 25 50 75 100 125 150

Junction temperature [˚C]

Operating current

Vcc =15V, after turn-on

RT=13.3kΩ, CT=1nF

DC=75%, Co=1nF

Figure 7. Reference voltage vs. load current.

Vref [V]

5.1

5.05

5

4.95

4.9 0 5 10 15 20 25

Vcc=15V Tj = 25°C

Iref [mA]

Figure 8. Vref vs. junction temperature.

Vref [V])

5.1

5.05

5

4.95

4.9

-50 -25 0 25 50 75 100 125 150

Vcc = 15V Iref = 1mA

Tj (°C

5/23

L5991 - L5991A

Figure 9. Vref vs. junction temperature.

Vref [V]

5.1

Vcc = 15V

5.05

5

4.95

4.9

-50 -25 0 25 50 75 100 125 150

Iref= 20mA

Tj (°C)

Figure 11. Output saturation.

Vsa t = V [V]

16

14

12

10

Vcc = Vc = 15V

Tj = 25°C

Figure 10. Vref SVRR vs. switching frequency.

SVRR (dB)

120

80

40

0

1 10 100 1000 10000

fsw (Hz)

Vcc=15V Vp-p=1V

Figure 12. Output saturation.

Vs at = V [V]

2.5

2

1.5

10

Vcc = Vc = 15V

Tj = 25°C

10

8

6

0 0.2 0.4 0.6 0.8 1 1.2

Isource [A]

Figure 13. UVLO Saturation

Ipin10 [mA] 50

40

30

20

10

0

Vcc < Vccon

before turn-on

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

Vp in 1 0 [mV]

1

0.5

0

0 0.2 0.4 0.6 0.8 1 1.2

Isink [A]

Figure 14. Timing resistor vs. switching frequency.

fsw (KHz) 5000

2000 1000

500

200 100

50

20 10

5.6nF

10 20 30 40

Vcc = 15V, V15 =0V Tj = 25°C

2.2nF

Rt (kohm)

100pF

220pF

470pF

1nF

6/23

)

L5991 - L5991A

Figure 15. Switching frequency vs. tempera-

ture.

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)

Figure 17. Dead time vs Ct.

Dea d time [ns]

1,500

1,200

900

600

300

Rt =4.5Kohm

V15 = 0V

V15 = Vref

Figure 16. Switching freque nc y v s. t emp er atu re .

fsw (KHz) 320

Rt= 4.5Kohm, Ct = 1nF

310

Vcc = 15V, V15= 0

300

290

280

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

Figure 18. Maximum Duty Cycle vs Vpin3.

DC Control Voltage Vpin3 [V]

3.5

V15 = 0V

2.5

1.5

V15 = Vref

3

2

Rt = 4.5Kohm, Ct = 1nF

246810

Timing capacitor Ct [nF]

Figure 19. Delay to out put vs jun ction temperat ure.

Delay to output (ns)

42

40

38

36

34

32

30

28

-50 -25 0 25 50 75 100 125 150 Tj (°C

PIN10 = OPEN

1V pulse on PIN13

1

0 102030405060708090100

Duty Cycle [%]

Figure 20. E/A frequency response.

G [dB]

150

100

50

0

0.01 0.1 1 10 10 0 1000 10000 100000 f (KHz)

Phase

140

120

100

80

60

40

20

7/23