AS1335 Ver la hoja de datos (PDF) - austriamicrosystems AG

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AS1335

1.5A, 1.5MHz, Synchronous DC/DC Step-Down Converter

austriamicrosystems AG 

AS1335

Datasheet - Detailed Description

8 Detailed Description

The AS1335 is a high-efficiency buck converter that uses a constant-frequency current-mode architecture. The device

contains two internal MOSFET switches and is available with a user-adjustable output voltage.

Figure 18. AS1335 - Block Diagram

Ramp

Compensator

–

OSC

ICOMP

VIN

lid OSCN

+

Frequency

a Shift

v FB

0.6V

+

Error

Amp

ill –

t 0.6V +

ΔVOVL

–

OVDET

+

G s –

A t EN

0.6V

Reference

0.6V -

ΔVOVL

+

s n Shutdown

Power-OK

Compare

e Logic

m t RSI

AS1335

Main

Digital

Logic

Anti-

Shoot

Through

+

IRCMP

–

SW

GND

POK

a n Main Control Loop

o During normal operation, the internal top power MOSFET is turned on each cycle when the oscillator sets the RS latch.

This switch is turned off when the current comparator (ICOMP) resets the RS latch. The peak inductor current (IPK) at

c which ICOMP resets the RS latch, is controlled by the error amplifier. When ILOAD increases, VFB decreases slightly

relative to the internal 0.6V reference, causing the error amplifier’s output voltage to increase until the average inductor

l current matches the new load current.

a When the top MOSFET is off, the bottom MOSFET is turned on until the inductor current starts to reverse as indicated

by the current reversal comparator (IRCMP), or the next clock cycle begins. The over-voltage detection comparator

ic (OVDET) guards against transient overshoots >7.8% by turning the main switch off and keeping it off until the transient

Techn is removed.

www.austriamicrosystems.com/DC-DC_Step-Down/AS1335

Revision 1.03

9 - 18

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