ST755 Ver la hoja de datos (PDF) - STMicroelectronics

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ST755

ADJUSTABLE INVERTING NEGATIVE OUTPUT CURRENT MODE PWM REGULATORS

STMicroelectronics 

ST755

APPLICATION CIRCUIT

To achieve the best performances from switching

power supply topology, particular care to layout

drawing is needed, in order to minimize EMI and

obtain low noise, jitter free operation moreover, it

ensures the full device functionality. Layout

design proposed on demoboard (see picture 2)

helps to lower the developing time.

Figure 1: TYPICAL APPLICATION CIRCUIT

Wire lengths must be minimized, filter and

by-pass capacitors C1, C2 and C3 must be low

ESR type, placed as close possible to the

integrated circuit. The 10µH inductor must be

chosen built on a core, taking care that saturation

current should be higher than the peak LX switch

current. See the PEAK INDUCTOR CURRENT

vs. LOAD CURRENT graph ( figure 6)

(*) R1 and R2 can be omitted for Iout<200mA.

(**) C6: Very low noise but poor transient and load response speed.

(***) C3 (alternative to C6): faster transient and load response.

Figure 2: Printed Demoboard

Component Values

Capacitor

C1

C2

C3

C4

C5

C6

4/9

Value

47

100

82

1

10

47

Unit

Resistor

µF

R1

µF

R2

pF

R3

µF

R4

µF

R5

pF

Symbol Pin

V CC

1

Vout

2

SHDN

3

GND

4

Value

Unit

130

KΩ

300

KΩ

10

KΩ

40.7

KΩ

10

KΩ

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