LX1571MYT データシートの表示（PDF） - Microsemi Corporation

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LX1571MYT

PHASE MODULATED AC SYNCHRONOUS SECONDARY-SIDE CONTROLLER

Microsemi Corporation 

LX1570/1571

PRODUCT DATABOOK 1996/1997

PHASE MODULATED AC SYNCHRONOUS SECONDARY-SIDE CONTROLLER

PR E L I M I N A RY D ATA S H E E T

Parameter

PWM Section

E.A. Output to PWM Drive Offset

Fixed Duty Cycle

Output Drive Section

Rise / Fall Time

Output HI

Output LO

Output Pull Down

UVLO Section

Start-Up Threshold

Turn Off Threshold

Hysterises

Supply Current Section

Dynamic Operating Current

Start-Up Current

E L E C T R I C A L C H A R A C T E R I S T I C S (Con't.)

Symbol

Test Conditions

VOFS

D

tR / tF

VDH

VDL

VDPD

CL = 1000pF

ISOURCE = 200mA, VCS = 0V, VFB = 2.3V

ISINK = 200mA, VCS = 1.2V, VFB = 2.3V

VCC = 0V, IPULL UP = 2mA

VST

VOFF

VH

IQd Out Freq = 100kHz, CL = 0

IST

LX1570/1571

Units

Min. Typ. Max.

1.7 2.0 2.4

V

52

54

56

%

50

ns

13.5

V

0.8

V

1

V

15

16

17

V

9

10

11

V

5.5

6

6.5

V

18

30

mA

150 250 µA

Pin

S.S.

VFB

COMP

C.S.

GND

OUT

DRV

VCC

CT

# Description

FUNCTIONAL PIN DESCRIPTION

1 This pin acts as the soft-start pin. A capacitor connected from this pin to GND allows slow ramp up of the NI input

resulting in output soft start during start up. This pin is clamped to the internal voltage reference during the normal

operation and sets the reference for the feedback regulator.

2 This pin is the inverting input of the Error Amplifier. It is normally connected to the switching power supply output

through a resistor divider to program the power supply voltage. This pin instead of the NI pin is internally trimed to

1% tolerance to include the offset voltage error of the error amp.

3 This pin is the Error Amplifier output and is made available for loop compensation. Typically a series R&C network

is connected from this pin to GND.

4 A voltage proportional to the inductor current is sensed by an external sense resistor (1570) or current transformer (1571)

in series with the return line and is connected to this pin. The output drive is terminated and latched off when this voltage

amplified by the internal gain (see option table) exceeds the voltage set by the E.A output voltage. The maximum

allowable voltage at this pin during normal operation is -0.8V typ for LX1570 and 6V typ for LX1571.

5 This pin is combined control circuitry and power GND. All other pins must be positive with respect to this pin, except

for C.S pin.

6 This pin drives a gate drive transformer which drives the power mosfet. A Schottky diode such as 1N5817 must be

connected from this pin to GND in order to prevent the substrate diode conduction.

7 This pin is the positive supply voltage for the control IC. A high frequency capacitor must be closely placed and

connected from this pin to GND to provide the turn-on and turn-off peak currents required for fast switching of the power

Mosfet.

8 The free running oscillator frequency is programmed by connecting a capacitor from this pin to GND.

4

Copyright © 1997

Rev. 0.9.3 1/97

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