L4990 Просмотр технического описания (PDF) - STMicroelectronics

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производитель

L4990

PRIMARY CONTROLLER

STMicroelectronics 

L4990 - L4990A

ELECTRICAL CHARACTERISTICS (continued.)

Symbol

Parameter

OUTPUT SECTION

VOL

Output Low Voltage

VOH

Output High Voltage

VOUT CLAMP

Output Clamp Voltage

Collector Leakage

Fall Time

Rise Time

UVLO Saturation

SUPPLY SECTION

VCCON

Startup voltage

VCCOFF Minimum Operating Voltage

Vh ys

Voltage After Turn-on Hysteresis

IS

Start Up Current

Iop

Operating Current

Iq

Quiescent Current

ISH

Shutdown Current

VZ

Zener Voltage

SYNCHRONIZATION SECTION

V1

Clock Amplitude

I1

Clock Source Current

V1

Sync Pulse

I1

Sync Pulse Current

OVER CURRENT PROTECTION

Vt

Fault Threshold Voltage

DISABLE SECTION

Shutdown threshold

Test Condition

IO = 250mA

IO = 20mA; VCC = 12V

IO = 200mA; VCC = 12V

IO = 5mA; VCC = 20V

VCC = 20V VC = 24V

CO = 1nF

CO = 2.5nF

CO = 1nF

CO = 2.5nF

VCC = 0V to VCCON; Isink = 10mA

L4990

L4990A

L4990

L4990A

L4990

L4990A

Before Turn-on at:

VCC = VCCON - 0.5V

CT = 1nF, RT = 4.42kΩ, CO =1nF

(After turn on), Co =0nF

CT = 1nF, RT = 4.42kΩ,

I8 = 20mA

Master Operation

ISOURCE = 0.8mA

Vclock = 3.5V

Slave Operation

Low Level

High Level

VSYNC = 3.5V

Min.

10

9

15

7.8

9

7

5.5

0.5

100

100

21

4

3.5

0.8

1.1

2.4

Typ.

10.5

10

13

100

20

35

50

70

16

8.4

10

7.6

6

0.8

270

12

7.0

270

25

7

1.2

2.5

Max.

1.0

200

60

100

1.0

17

9

11

8.2

450

18

10

450

30

1

1.3

2.6

Unit

V

V

V

V

µA

ns

ns

ns

ns

V

V

V

V

v

V

v

µA

mA

mA

µA

V

V

mA

V

V

mA

V

V

FUNCTIONAL DESCRIPTION

The I.C. contains a standard PWM current mode

control section with improved performance with

respect to the UC384X family.

Enhanced features include start-up bias current

reduced to < 270µA (typ), improved E/A perform-

ance (4MHz B/W, 1.3mA Source Current, high-

slew rate) accurate 1MHz oscillator, and also re-

duced propagation delays in the critical path from

Current Sense to Output.

4/24

ADDITIONAL FEATURES

Soft Start (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 func-

tion as described below.

Current Limit / Reset Delay

An internal high-speed current limit comparator

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