Rev 1.1a

Copyright

© 1994

11861 Western Avenue

∞

∞

∞

∞

∞ Garden Grove, CA 92841

3

(714) 898-8121

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LO Output

1.0

0.5

.01

.3

1.0

0.5

V

I

Off Leakage

On Voltage

SG1549/SG2549/SG3549

(V

S

= 5V, T

A

= 25

°C)

Reset Minimum Pulse Width (T

Delay from Reset to LO Output (T

LO Input Minimum Pulse Width (T

Delay from LO Input to LO Output (T

Delay from HI Input to LO Output (T

Delay from HI Output to LO Output

ns

ns

ns

ns

ns

ns

300

600

300

360

900

60

150

300

50

180

300

30

Min. Typ. Max.

SG1549 Series

Test Conditions

Parameter

Units

DYNAMIC TEST CIRCUIT

SWITCHING WAVEFORMS

APPLICATION NOTES

HIGH LINE SENSING - The SG1549 will provide current sensing in the

positive supply line in the typical SG1524 single-ended switching

regulator application shown in Figure 1. The HI CM sense circuitry can

be used with input voltages between 2 and 40 volts.

A value for R

the peak current desired. High-frequency noise, or switching transients,

can usually be eliminated by a small capacitor between pins 3 and 4.

Current control may be accomplished by either the HI OUTPUT pin

connected to the SG1524’s Shutdown pin, or the LO OUTPUT pin

connected directly to the Compensation Terminal.

In either case,

activation of the current sense latch will tend to discharge the compen-

sation capacitor, C

If this feature is desired, the LO OUTPUT pin may be used to discharge

a soft-start network instead of coupling directly to the SG1524. If it is not

desired, the use of a small value of C

will enhance recovery.

ELECTRICAL CHARACTERISTICS

(V

5V, and over recomended operating temperature, unless otherwise specified.)

Min. Typ. Max. Min. Typ. Max.

SG3549

SG1549/2549

Test Conditions

Parameter

Units

Amplitude = 3.0V

R

LO CM Amplitude = 200mV

LO CM Amplitude = 200mV, R

Amplitude = 200mV, V

LO CM Input = 200mV

Off Voltage

On Voltage

0

3.2

0.1

V

V

0

3.2

0.1

I

2.8

Note 4: These parameters, although guaranteed, are not tested in production.

FIGURE 1 — HIGH LINE SENSING WITH THE SG1549 IN CONJUNCTION

WITH AN SG1524 PWM CONTROL IC

HI Output Section

2.8

.01

.3

µA

V